bionic (5) procfs.5.gz

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NAME

       proc - process information pseudo-filesystem

DESCRIPTION

       The  proc filesystem is a pseudo-filesystem which provides an interface to kernel data structures.  It is
       commonly mounted at /proc.  Typically, it is mounted automatically by the system,  but  it  can  also  be
       mounted manually using a command such as:

           mount -t proc proc /proc

       Most  of  the  files  in  the proc filesystem are read-only, but some files are writable, allowing kernel
       variables to be changed.

   Mount options
       The proc filesystem supports the following mount options:

       hidepid=n (since Linux 3.3)
              This option controls who can access the information in /proc/[pid] directories.  The argument,  n,
              is one of the following values:

              0   Everybody  may  access all /proc/[pid] directories.  This is the traditional behavior, and the
                  default if this mount option is not specified.

              1   Users may not access files and subdirectories inside any /proc/[pid] directories but their own
                  (the   /proc/[pid]   directories   themselves   remain  visible).   Sensitive  files  such  as
                  /proc/[pid]/cmdline and /proc/[pid]/status are now protected against other users.  This  makes
                  it  impossible to learn whether any user is running a specific program (so long as the program
                  doesn't otherwise reveal itself by its behavior).

              2   As for mode 1, but in addition the /proc/[pid] directories belonging  to  other  users  become
                  invisible.   This means that /proc/[pid] entries can no longer be used to discover the PIDs on
                  the system.  This doesn't hide the fact that a process with a specific PID  value  exists  (it
                  can  be  learned by other means, for example, by "kill -0 $PID"), but it hides a process's UID
                  and GID, which could otherwise be learned by employing stat(2)  on  a  /proc/[pid]  directory.
                  This  greatly  complicates an attacker's task of gathering information about running processes
                  (e.g., discovering whether some daemon is running with elevated  privileges,  whether  another
                  user  is  running  some sensitive program, whether other users are running any program at all,
                  and so on).

       gid=gid (since Linux 3.3)
              Specifies the ID of a group whose members are authorized to learn  process  information  otherwise
              prohibited  by  hidepid  (i.e.,  users  in  this  group  behave  as  though /proc was mounted with
              hidepid=0).  This group should be used instead of approaches such as putting  nonroot  users  into
              the sudoers(5) file.

   Files and directories
       The following list describes many of the files and directories under the /proc hierarchy.

       /proc/[pid]
              There  is  a  numerical  subdirectory  for  each running process; the subdirectory is named by the
              process ID.

              Each /proc/[pid] subdirectory contains the pseudo-files and directories  described  below.   These
              files are normally owned by the effective user and effective group ID of the process.  However, as
              a security measure, the ownership is made root:root if the process's "dumpable" attribute  is  set
              to a value other than 1.  This attribute may change for the following reasons:

              *  The attribute was explicitly set via the prctl(2) PR_SET_DUMPABLE operation.

              *  The  attribute was reset to the value in the file /proc/sys/fs/suid_dumpable (described below),
                 for the reasons described in prctl(2).

              Resetting the "dumpable" attribute to 1 reverts the ownership of the /proc/[pid]/*  files  to  the
              process's real UID and real GID.

       /proc/[pid]/attr
              The  files  in this directory provide an API for security modules.  The contents of this directory
              are files that can be read  and  written  in  order  to  set  security-related  attributes.   This
              directory  was  added  to support SELinux, but the intention was that the API be general enough to
              support other security modules.  For the purpose of explanation,  examples  of  how  SELinux  uses
              these files are provided below.

              This directory is present only if the kernel was configured with CONFIG_SECURITY.

       /proc/[pid]/attr/current (since Linux 2.6.0)
              The contents of this file represent the current security attributes of the process.

              In  SELinux,  this  file is used to get the security context of a process.  Prior to Linux 2.6.11,
              this file could not be used to set the security context (a write was always denied), since SELinux
              limited  process  security transitions to execve(2) (see the description of /proc/[pid]/attr/exec,
              below).  Since Linux 2.6.11, SELinux lifted this restriction and began supporting "set" operations
              via  writes  to this node if authorized by policy, although use of this operation is only suitable
              for applications that are trusted to maintain any desired  separation  between  the  old  and  new
              security  contexts.   Prior to Linux 2.6.28, SELinux did not allow threads within a multi-threaded
              process to set their security context via this node as it would yield an inconsistency  among  the
              security  contexts  of  the  threads  sharing  the same memory space.  Since Linux 2.6.28, SELinux
              lifted this restriction and began supporting "set" operations for threads within  a  multithreaded
              process  if  the  new  security  context is bounded by the old security context, where the bounded
              relation is defined in policy and guarantees that the new security context has  a  subset  of  the
              permissions  of  the  old  security  context.   Other security modules may choose to support "set"
              operations via writes to this node.

       /proc/[pid]/attr/exec (since Linux 2.6.0)
              This file represents the attributes to assign to the process upon a subsequent execve(2).

              In SELinux, this is needed to support role/domain transitions,  and  execve(2)  is  the  preferred
              point  to  make  such  transitions because it offers better control over the initialization of the
              process in the new security label and the inheritance of state.  In  SELinux,  this  attribute  is
              reset on execve(2) so that the new program reverts to the default behavior for any execve(2) calls
              that it may make.  In SELinux, a process can set only its own /proc/[pid]/attr/exec attribute.

       /proc/[pid]/attr/fscreate (since Linux 2.6.0)
              This file represents the attributes to assign to files created by  subsequent  calls  to  open(2),
              mkdir(2), symlink(2), and mknod(2)

              SELinux employs this file to support creation of a file (using the aforementioned system calls) in
              a secure state, so that there is no risk of inappropriate access being obtained between  the  time
              of  creation  and  the  time  that  attributes  are  set.   In SELinux, this attribute is reset on
              execve(2), so that the new program reverts to the default behavior for any file creation calls  it
              may  make,  but  the  attribute  will persist across multiple file creation calls within a program
              unless  it  is   explicitly   reset.    In   SELinux,   a   process   can   set   only   its   own
              /proc/[pid]/attr/fscreate attribute.

       /proc/[pid]/attr/keycreate (since Linux 2.6.18)
              If  a process writes a security context into this file, all subsequently created keys (add_key(2))
              will be labeled  with  this  context.   For  further  information,  see  the  kernel  source  file
              Documentation/security/keys/core.rst (or file Documentation/security/keys.txt on Linux between 3.0
              and 4.13, or Documentation/keys.txt before Linux 3.0).

       /proc/[pid]/attr/prev (since Linux 2.6.0)
              This file contains the security context of the process before the last  execve(2);  that  is,  the
              previous value of /proc/[pid]/attr/current.

       /proc/[pid]/attr/socketcreate (since Linux 2.6.18)
              If  a  process  writes a security context into this file, all subsequently created sockets will be
              labeled with this context.

       /proc/[pid]/autogroup (since Linux 2.6.38)
              See sched(7).

       /proc/[pid]/auxv (since 2.6.0-test7)
              This contains the contents of the ELF interpreter information passed to the process at exec  time.
              The  format  is  one unsigned long ID plus one unsigned long value for each entry.  The last entry
              contains two zeros.  See also getauxval(3).

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

       /proc/[pid]/cgroup (since Linux 2.6.24)
              See cgroups(7).

       /proc/[pid]/clear_refs (since Linux 2.6.22)

              This is a write-only file, writable only by owner of the process.

              The following values may be written to the file:

              1 (since Linux 2.6.22)
                     Reset  the  PG_Referenced  and  ACCESSED/YOUNG  bits  for all the pages associated with the
                     process.  (Before kernel 2.6.32, writing any nonzero value to this file had this effect.)

              2 (since Linux 2.6.32)
                     Reset the PG_Referenced and ACCESSED/YOUNG bits for all anonymous pages associated with the
                     process.

              3 (since Linux 2.6.32)
                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all file-mapped pages associated with
                     the process.

              Clearing the PG_Referenced and ACCESSED/YOUNG bits provides a method to measure approximately  how
              much  memory a process is using.  One first inspects the values in the "Referenced" fields for the
              VMAs shown in /proc/[pid]/smaps to get an idea of the memory footprint of the process.   One  then
              clears  the  PG_Referenced  and  ACCESSED/YOUNG  bits and, after some measured time interval, once
              again inspects the values in the "Referenced" fields to get  an  idea  of  the  change  in  memory
              footprint  of  the  process during the measured interval.  If one is interested only in inspecting
              the selected mapping types, then the value 2 or 3 can be used instead of 1.

              Further values can be written to affect different properties:

              4 (since Linux 3.11)
                     Clear the soft-dirty bit for all the pages associated with the process.  This is  used  (in
                     conjunction  with  /proc/[pid]/pagemap) by the check-point restore system to discover which
                     pages of a process have been dirtied since the file /proc/[pid]/clear_refs was written to.

              5 (since Linux 4.0)
                     Reset the peak resident set size ("high water mark") to the process's current resident  set
                     size value.

              Writing any value to /proc/[pid]/clear_refs other than those listed above has no effect.

              The   /proc/[pid]/clear_refs   file   is  present  only  if  the  CONFIG_PROC_PAGE_MONITOR  kernel
              configuration option is enabled.

       /proc/[pid]/cmdline
              This read-only file holds the complete command line for the  process,  unless  the  process  is  a
              zombie.   In  the  latter  case,  there is nothing in this file: that is, a read on this file will
              return 0 characters.  The command-line arguments appear in this file as a set of strings separated
              by null bytes ('\0'), with a further null byte after the last string.

       /proc/[pid]/comm (since Linux 2.6.33)
              This  file exposes the process's comm value—that is, the command name associated with the process.
              Different  threads  in  the  same  process  may  have  different  comm  values,   accessible   via
              /proc/[pid]/task/[tid]/comm.   A  thread may modify its comm value, or that of any of other thread
              in the same thread group (see the discussion of CLONE_THREAD in clone(2)), by writing to the  file
              /proc/self/task/[tid]/comm.   Strings  longer  than  TASK_COMM_LEN  (16)  characters  are silently
              truncated.

              This file provides a superset of the prctl(2)  PR_SET_NAME  and  PR_GET_NAME  operations,  and  is
              employed by pthread_setname_np(3) when used to rename threads other than the caller.

       /proc/[pid]/coredump_filter (since Linux 2.6.23)
              See core(5).

       /proc/[pid]/cpuset (since Linux 2.6.12)
              See cpuset(7).

       /proc/[pid]/cwd
              This  is a symbolic link to the current working directory of the process.  To find out the current
              working directory of process 20, for instance, you can do this:

                  $ cd /proc/20/cwd; /bin/pwd

              Note that the pwd command is often a shell built-in, and might not work properly.  In bash(1), you
              may use pwd -P.

              In  a  multithreaded  process,  the  contents  of this symbolic link are not available if the main
              thread has already terminated (typically by calling pthread_exit(3)).

              Permission to dereference or read (readlink(2)) this symbolic link is governed by a ptrace  access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/environ
              This  file  contains the initial environment that was set when the currently executing program was
              started via execve(2).  The entries are separated by null bytes ('\0'), and there may  be  a  null
              byte at the end.  Thus, to print out the environment of process 1, you would do:

                  $ strings /proc/1/environ

              If,  after  an execve(2), the process modifies its environment (e.g., by calling functions such as
              putenv(3) or modifying the environ(7)  variable  directly),  this  file  will  not  reflect  those
              changes.

              Furthermore,  a  process  may  change  the  memory  location  that  this  file refers via prctl(2)
              operations such as PR_SET_MM_ENV_START.

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

       /proc/[pid]/exe
              Under  Linux  2.2  and  later,  this file is a symbolic link containing the actual pathname of the
              executed command.  This symbolic link can be dereferenced normally; attempting  to  open  it  will
              open the executable.  You can even type /proc/[pid]/exe to run another copy of the same executable
              that is being run by process [pid].  If the pathname has been unlinked,  the  symbolic  link  will
              contain the string '(deleted)' appended to the original pathname.  In a multithreaded process, the
              contents of this symbolic link are not  available  if  the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

              Permission  to dereference or read (readlink(2)) this symbolic link is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

              Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the binary which  was  executed,  and
              appears  as  a symbolic link.  A readlink(2) call on this file under Linux 2.0 returns a string in
              the format:

                  [device]:inode

              For example, [0301]:1502 would be inode 1502 on device major 03 (IDE, MFM, etc. drives)  minor  01
              (first partition on the first drive).

              find(1) with the -inum option can be used to locate the file.

       /proc/[pid]/fd/
              This is a subdirectory containing one entry for each file which the process has open, named by its
              file descriptor, and which is a symbolic link to the actual file.  Thus, 0 is  standard  input,  1
              standard output, 2 standard error, and so on.

              For  file  descriptors  for pipes and sockets, the entries will be symbolic links whose content is
              the file type with the inode.  A readlink(2) call on this file returns a string in the format:

                  type:[inode]

              For example, socket:[2248868] will be a socket and its inode is 2248868.  For sockets, that  inode
              can be used to find more information in one of the files under /proc/net/.

              For  file descriptors that have no corresponding inode (e.g., file descriptors produced by bpf(2),
              epoll_create(2), eventfd(2), inotify_init(2), perf_event_open(2), signalfd(2),  timerfd_create(2),
              and userfaultfd(2)), the entry will be a symbolic link with contents of the form

                  anon_inode:<file-type>

              In many cases (but not all), the file-type is surrounded by square brackets.

              For  example,  an  epoll  file  descriptor  will  have a symbolic link whose content is the string
              anon_inode:[eventpoll].

              In a multithreaded process, the contents of this directory are not available if  the  main  thread
              has already terminated (typically by calling pthread_exit(3)).

              Programs that take a filename as a command-line argument, but don't take input from standard input
              if no argument is supplied, and programs that write to a file named as  a  command-line  argument,
              but  don't  send  their  output to standard output if no argument is supplied, can nevertheless be
              made to use standard input or standard  output  by  using  /proc/[pid]/fd  files  as  command-line
              arguments.  For example, assuming that -i is the flag designating an input file and -o is the flag
              designating an output file:

                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

              and you have a working filter.

              /proc/self/fd/N is approximately the same as /dev/fd/N in some UNIX and UNIX-like  systems.   Most
              Linux MAKEDEV scripts symbolically link /dev/fd to /proc/self/fd, in fact.

              Most  systems  provide symbolic links /dev/stdin, /dev/stdout, and /dev/stderr, which respectively
              link to the files 0, 1, and 2 in /proc/self/fd.  Thus the example command above could  be  written
              as:

                  $ foobar -i /dev/stdin -o /dev/stdout ...

              Permission  to  dereference or read (readlink(2)) the symbolic links in this directory is governed
              by a ptrace access mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

              Note that for file descriptors referring to inodes (pipes and sockets, see  above),  those  inodes
              still  have  permission  bits  and ownership information distinct from those of the /proc/[pid]/fd
              entry, and that the owner may differ from the user and group IDs of the process.  An  unprivileged
              process may lack permissions to open them, as in this example:

                  $ echo test | sudo -u nobody cat
                  test
                  $ echo test | sudo -u nobody cat /proc/self/fd/0
                  cat: /proc/self/fd/0: Permission denied

              File descriptor 0 refers to the pipe created by the shell and owned by that shell's user, which is
              not nobody, so cat does not have permission to create a new file  descriptor  to  read  from  that
              inode, even though it can still read from its existing file descriptor 0.

       /proc/[pid]/fdinfo/ (since Linux 2.6.22)
              This is a subdirectory containing one entry for each file which the process has open, named by its
              file descriptor.  The files in this directory are readable only by the owner of the process.   The
              contents  of  each file can be read to obtain information about the corresponding file descriptor.
              The content depends on the type of file referred to by the corresponding file descriptor.

              For regular files and directories, we see something like:

                  $ cat /proc/12015/fdinfo/4
                  pos:    1000
                  flags:  01002002
                  mnt_id: 21

              The fields are as follows:

              pos    This is a decimal number showing the file offset.

              flags  This is an octal number that displays the file access  mode  and  file  status  flags  (see
                     open(2)).   If  the close-on-exec file descriptor flag is set, then flags will also include
                     the value O_CLOEXEC.

                     Before Linux 3.1, this field incorrectly displayed the setting of O_CLOEXEC at the time the
                     file was opened, rather than the current setting of the close-on-exec flag.

              mnt_id This  field,  present  since Linux 3.15, is the ID of the mount point containing this file.
                     See the description of /proc/[pid]/mountinfo.

              For eventfd file descriptors (see eventfd(2)), we see (since Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  eventfd-count:               40

              eventfd-count is the current value of the eventfd counter, in hexadecimal.

              For epoll file descriptors (see epoll(7)), we see (since Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  tfd:        9 events:       19 data: 74253d2500000009
                  tfd:        7 events:       19 data: 74253d2500000007

              Each of the lines beginning tfd describes one of the file  descriptors  being  monitored  via  the
              epoll  file  descriptor  (see  epoll_ctl(2) for some details).  The tfd field is the number of the
              file descriptor.  The events field is a hexadecimal mask of the events being  monitored  for  this
              file descriptor.  The data field is the data value associated with this file descriptor.

              For signalfd file descriptors (see signalfd(2)), we see (since Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  sigmask:  0000000000000006

              sigmask  is  the  hexadecimal mask of signals that are accepted via this signalfd file descriptor.
              (In this example, bits 2 and 3 are set, corresponding to  the  signals  SIGINT  and  SIGQUIT;  see
              signal(7).)

              For inotify file descriptors (see inotify(7)), we see (since Linux 3.8) the following fields:

                  pos: 0
                  flags:    00
                  mnt_id:   11
                  inotify wd:2 ino:7ef82a sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:2af87e00220ffd73
                  inotify wd:1 ino:192627 sdev:800001 mask:800afff ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:27261900802dfd73

              Each  of  the lines beginning with "inotify" displays information about one file or directory that
              is being monitored.  The fields in this line are as follows:

              wd     A watch descriptor number (in decimal).

              ino    The inode number of the target file (in hexadecimal).

              sdev   The ID of the device where the target file resides (in hexadecimal).

              mask   The mask of events being monitored for the target file (in hexadecimal).

              If the kernel was built with exportfs support, the path to the target file is exposed  as  a  file
              handle, via three hexadecimal fields: fhandle-bytes, fhandle-type, and f_handle.

              For fanotify file descriptors (see fanotify(7)), we see (since Linux 3.8) the following fields:

                  pos: 0
                  flags:    02
                  mnt_id:   11
                  fanotify flags:0 event-flags:88002
                  fanotify ino:19264f sdev:800001 mflags:0 mask:1 ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:4f261900a82dfd73

              The   fourth   line  displays  information  defined  when  the  fanotify  group  was  created  via
              fanotify_init(2):

              flags  The flags argument given to fanotify_init(2) (expressed in hexadecimal).

              event-flags
                     The event_f_flags argument given to fanotify_init(2) (expressed in hexadecimal).

              Each additional line shown in the file contains information about one of the marks in the fanotify
              group.  Most of these fields are as for inotify, except:

              mflags The flags associated with the mark (expressed in hexadecimal).

              mask   The events mask for this mark (expressed in hexadecimal).

              ignored_mask
                     The mask of events that are ignored for this mark (expressed in hexadecimal).

              For details on these fields, see fanotify_mark(2).

       /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/io (since kernel 2.6.20)
              This file contains I/O statistics for the process, for example:

                  # cat /proc/3828/io
                  rchar: 323934931
                  wchar: 323929600
                  syscr: 632687
                  syscw: 632675
                  read_bytes: 0
                  write_bytes: 323932160
                  cancelled_write_bytes: 0

              The fields are as follows:

              rchar: characters read
                     The number of bytes which this task has caused to be read from storage.  This is simply the
                     sum of bytes which this process passed to read(2) and similar system  calls.   It  includes
                     things  such  as  terminal I/O and is unaffected by whether or not actual physical disk I/O
                     was required (the read might have been satisfied from pagecache).

              wchar: characters written
                     The number of bytes which this task has caused, or shall  cause  to  be  written  to  disk.
                     Similar caveats apply here as with rchar.

              syscr: read syscalls
                     Attempt  to  count  the number of read I/O operations—that is, system calls such as read(2)
                     and pread(2).

              syscw: write syscalls
                     Attempt to count the number of write I/O operations—that is, system calls such as  write(2)
                     and pwrite(2).

              read_bytes: bytes read
                     Attempt to count the number of bytes which this process really did cause to be fetched from
                     the storage layer.  This is accurate for block-backed filesystems.

              write_bytes: bytes written
                     Attempt to count the number of bytes which this process caused to be sent  to  the  storage
                     layer.

              cancelled_write_bytes:
                     The  big  inaccuracy  here is truncate.  If a process writes 1MB to a file and then deletes
                     the file, it will in fact perform no writeout.  But it will have been accounted  as  having
                     caused  1MB of write.  In other words: this field represents the number of bytes which this
                     process caused to not happen, by truncating pagecache.  A task  can  cause  "negative"  I/O
                     too.   If  this  task  truncates some dirty pagecache, some I/O which another task has been
                     accounted for (in its write_bytes) will not be happening.

              Note: In the current implementation, things are a bit racy on 32-bit systems: if process  A  reads
              process  B's  /proc/[pid]/io  while  process B is updating one of these 64-bit counters, process A
              could see an intermediate result.

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

       /proc/[pid]/limits (since Linux 2.6.24)
              This  file displays the soft limit, hard limit, and units of measurement for each of the process's
              resource limits (see getrlimit(2)).  Up to and including Linux 2.6.35, this file is  protected  to
              allow  reading  only by the real UID of the process.  Since Linux 2.6.36, this file is readable by
              all users on the system.

       /proc/[pid]/map_files/ (since kernel 3.3)
              This subdirectory contains entries corresponding to memory-mapped files  (see  mmap(2)).   Entries
              are  named by memory region start and end address pair (expressed as hexadecimal numbers), and are
              symbolic links to the mapped files themselves.  Here is an example, with the  output  wrapped  and
              reformatted to fit on an 80-column display:

                  # ls -l /proc/self/map_files/
                  lr--------. 1 root root 64 Apr 16 21:31
                              3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
                  ...

              Although these entries are present for memory regions that were mapped with the MAP_FILE flag, the
              way anonymous shared memory (regions created with the MAP_ANON | MAP_SHARED flags) is  implemented
              in  Linux  means  that  such  regions also appear on this directory.  Here is an example where the
              target file is the deleted /dev/zero one:

                  lrw-------. 1 root root 64 Apr 16 21:33
                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

              This directory appears only  if  the  CONFIG_CHECKPOINT_RESTORE  kernel  configuration  option  is
              enabled.  Privilege (CAP_SYS_ADMIN) is required to view the contents of this directory.

       /proc/[pid]/maps
              A  file  containing the currently mapped memory regions and their access permissions.  See mmap(2)
              for some further information about memory mappings.

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

              The format of the file is:

    address           perms offset  dev   inode       pathname
    00400000-00452000 r-xp 00000000 08:02 173521      /usr/bin/dbus-daemon
    00651000-00652000 r--p 00051000 08:02 173521      /usr/bin/dbus-daemon
    00652000-00655000 rw-p 00052000 08:02 173521      /usr/bin/dbus-daemon
    00e03000-00e24000 rw-p 00000000 00:00 0           [heap]
    00e24000-011f7000 rw-p 00000000 00:00 0           [heap]
    ...
    35b1800000-35b1820000 r-xp 00000000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a20000-35b1a21000 rw-p 00020000 08:02 135522  /usr/lib64/ld-2.15.so
    35b1a21000-35b1a22000 rw-p 00000000 00:00 0
    35b1c00000-35b1dac000 r-xp 00000000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1dac000-35b1fac000 ---p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
    35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870  /usr/lib64/libc-2.15.so
    ...
    f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0    [stack:986]
    ...
    7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0   [stack]
    7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0   [vdso]

              The  address field is the address space in the process that the mapping occupies.  The perms field
              is a set of permissions:

                  r = read
                  w = write
                  x = execute
                  s = shared
                  p = private (copy on write)

              The offset field is the offset into the file/whatever; dev is the device (major:minor);  inode  is
              the  inode  on  that  device.   0 indicates that no inode is associated with the memory region, as
              would be the case with BSS (uninitialized data).

              The pathname field will usually be the file that is backing the mapping.  For ELF files,  you  can
              easily  coordinate with the offset field by looking at the Offset field in the ELF program headers
              (readelf -l).

              There are additional helpful pseudo-paths:

                   [stack]
                          The initial process's (also known as the main thread's) stack.

                   [stack:<tid>] (since Linux 3.4)
                          A  thread's  stack  (where  the  <tid>  is  a  thread  ID).   It  corresponds  to  the
                          /proc/[pid]/task/[tid]/ path.

                   [vdso] The virtual dynamically linked shared object.  See vdso(7).

                   [heap] The process's heap.

              If the pathname field is blank, this is an anonymous mapping as obtained via mmap(2).  There is no
              easy way to coordinate this back to a process's  source,  short  of  running  it  through  gdb(1),
              strace(1), or similar.

              Under Linux 2.0, there is no field giving pathname.

       /proc/[pid]/mem
              This  file  can  be  used  to access the pages of a process's memory through open(2), read(2), and
              lseek(2).

              Permission to access this file is governed by  a  ptrace  access  mode  PTRACE_MODE_ATTACH_FSCREDS
              check; see ptrace(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
              This  file  contains  information  about  mount  points  in  the  process's  mount  namespace (see
              mount_namespaces(7)).  It supplies various information (e.g., propagation state, root of mount for
              bind  mounts,  identifier  for  each  mount  and  its  parent)  that  is  missing from the (older)
              /proc/[pid]/mounts file, and fixes various other problems with that file (e.g.,  nonextensibility,
              failure to distinguish per-mount versus per-superblock options).

              The file contains lines of the form:
(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The numbers in parentheses are labels for the descriptions below:

              (1)  mount ID: a unique ID for the mount (may be reused after umount(2)).

              (2)  parent  ID:  the  ID  of  the parent mount (or of self for the root of this mount namespace's
                   mount tree).

                   If the parent mount point lies outside the process's root directory (see chroot(2)),  the  ID
                   shown  here  won't  have a corresponding record in mountinfo whose mount ID (field 1) matches
                   this parent mount ID (because mount points that lie outside the process's root directory  are
                   not shown in mountinfo).  As a special case of this point, the process's root mount point may
                   have a parent mount (for the initramfs filesystem)  that  lies  outside  the  process's  root
                   directory, and an entry for that mount point will not appear in mountinfo.

              (3)  major:minor: the value of st_dev for files on this filesystem (see stat(2)).

              (4)  root: the pathname of the directory in the filesystem which forms the root of this mount.

              (5)  mount point: the pathname of the mount point relative to the process's root directory.

              (6)  mount options: per-mount options.

              (7)  optional fields: zero or more fields of the form "tag[:value]"; see below.

              (8)  separator: the end of the optional fields is marked by a single hyphen.

              (9)  filesystem type: the filesystem type in the form "type[.subtype]".

              (10) mount source: filesystem-specific information or "none".

              (11) super options: per-superblock options.

              Currently,  the  possible optional fields are shared, master, propagate_from, and unbindable.  See
              mount_namespaces(7) for a description of these fields.  Parsers  should  ignore  all  unrecognized
              optional fields.

              For  more information on mount propagation see: Documentation/filesystems/sharedsubtree.txt in the
              Linux kernel source tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
              This file lists all the filesystems currently  mounted  in  the  process's  mount  namespace  (see
              mount_namespaces(7)).  The format of this file is documented in fstab(5).

              Since  kernel  version 2.6.15, this file is pollable: after opening the file for reading, a change
              in this file (i.e., a filesystem mount or unmount) causes select(2) to mark the file descriptor as
              having  an exceptional condition, and poll(2) and epoll_wait(2) mark the file as having a priority
              event (POLLPRI).  (Before Linux 2.6.30, a change in this file was indicated by the file descriptor
              being  marked as readable for select(2), and being marked as having an error condition for poll(2)
              and epoll_wait(2).)

       /proc/[pid]/mountstats (since Linux 2.6.17)
              This file exports information (statistics, configuration information) about the  mount  points  in
              the process's mount namespace (see mount_namespaces(7)).  Lines in this file have the form:

                  device /dev/sda7 mounted on /home with fstype ext3 [statistics]
                  (       1      )            ( 2 )             (3 ) (4)

              The fields in each line are:

              (1)  The name of the mounted device (or "nodevice" if there is no corresponding device).

              (2)  The mount point within the filesystem tree.

              (3)  The filesystem type.

              (4)  Optional  statistics and configuration information.  Currently (as at Linux 2.6.26), only NFS
                   filesystems export information via this field.

              This file is readable only by the owner of the process.

       /proc/[pid]/net (since Linux 2.6.25)
              See the description of /proc/net.

       /proc/[pid]/ns/ (since Linux 3.0)
              This is a subdirectory containing one entry for each namespace that supports being manipulated  by
              setns(2).  For more information, see namespaces(7).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
              See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
              This file can be used to adjust the score used to select which process should be killed in an out-
              of-memory (OOM) situation.  The kernel uses this value for a bit-shift operation of the  process's
              oom_score  value:  valid  values  are  in  the range -16 to +15, plus the special value -17, which
              disables OOM-killing altogether for this process.  A positive score increases  the  likelihood  of
              this process being killed by the OOM-killer; a negative score decreases the likelihood.

              The  default  value  for  this  file is 0; a new process inherits its parent's oom_adj setting.  A
              process must be privileged (CAP_SYS_RESOURCE) to update this file.

              Since Linux 2.6.36, use of this file is deprecated in favor of /proc/[pid]/oom_score_adj.

       /proc/[pid]/oom_score (since Linux 2.6.11)
              This file displays the current score that the kernel gives to this  process  for  the  purpose  of
              selecting  a  process for the OOM-killer.  A higher score means that the process is more likely to
              be selected by the OOM-killer.  The basis for this score is the  amount  of  memory  used  by  the
              process, with increases (+) or decreases (-) for factors including:

              * whether the process is privileged (-).

              Before kernel 2.6.36 the following factors were also used in the calculation of oom_score:

              * whether the process creates a lot of children using fork(2) (+);

              * whether the process has been running a long time, or has used a lot of CPU time (-);

              * whether the process has a low nice value (i.e., > 0) (+); and

              * whether the process is making direct hardware access (-).

              The  oom_score  also reflects the adjustment specified by the oom_score_adj or oom_adj setting for
              the process.

       /proc/[pid]/oom_score_adj (since Linux 2.6.36)
              This file can be used to adjust the badness heuristic used to select which process gets killed  in
              out-of-memory conditions.

              The  badness  heuristic assigns a value to each candidate task ranging from 0 (never kill) to 1000
              (always kill) to determine which process is targeted.  The units are roughly  a  proportion  along
              that  range of allowed memory the process may allocate from, based on an estimation of its current
              memory and swap use.  For example, if a task is using all allowed memory, its badness  score  will
              be 1000.  If it is using half of its allowed memory, its score will be 500.

              There  is  an  additional  factor included in the badness score: root processes are given 3% extra
              memory over other tasks.

              The amount of "allowed" memory depends on the context in which the OOM-killer was called.   If  it
              is  due to the memory assigned to the allocating task's cpuset being exhausted, the allowed memory
              represents the set of mems assigned to that cpuset (see cpuset(7)).  If it is due to a mempolicy's
              node(s)  being  exhausted, the allowed memory represents the set of mempolicy nodes.  If it is due
              to a memory limit (or swap limit) being reached, the allowed  memory  is  that  configured  limit.
              Finally,  if it is due to the entire system being out of memory, the allowed memory represents all
              allocatable resources.

              The value of oom_score_adj is added to the badness score before it is used to determine which task
              to  kill.   Acceptable  values  range from -1000 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).
              This allows user space to control the preference for OOM-killing, ranging from always preferring a
              certain  task  or  completely disabling it from OOM killing.  The lowest possible value, -1000, is
              equivalent to disabling OOM-killing entirely for that task, since it will always report a  badness
              score of 0.

              Consequently, it is very simple for user space to define the amount of memory to consider for each
              task.  Setting an oom_score_adj value of +500, for example, is roughly equivalent to allowing  the
              remainder  of  tasks sharing the same system, cpuset, mempolicy, or memory controller resources to
              use at least 50% more memory.  A value of -500, on the other hand, would be roughly equivalent  to
              discounting 50% of the task's allowed memory from being considered as scoring against the task.

              For  backward  compatibility  with previous kernels, /proc/[pid]/oom_adj can still be used to tune
              the badness score.  Its value is scaled linearly with oom_score_adj.

              Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will change the other with its  scaled
              value.

       /proc/[pid]/pagemap (since Linux 2.6.25)
              This  file  shows  the mapping of each of the process's virtual pages into physical page frames or
              swap area.  It contains one 64-bit value for each virtual page, with the bits set as follows:

                   63     If set, the page is present in RAM.

                   62     If set, the page is in swap space

                   61 (since Linux 3.5)
                          The page is a file-mapped page or a shared anonymous page.

                   60–57 (since Linux 3.11)
                          Zero

                   56 (since Linux 4.2)
                          The page is exclusively mapped.

                   55 (since Linux 3.11)
                          PTE is soft-dirty (see the kernel source file Documentation/vm/soft-dirty.txt).

                   54–0   If the page is present in RAM (bit 63), then these bits provide the page frame number,
                          which  can  be  used  to  index /proc/kpageflags and /proc/kpagecount.  If the page is
                          present in swap (bit 62), then bits 4–0 give the swap type, and bits 54–5  encode  the
                          swap offset.

              Before Linux 3.11, bits 60–55 were used to encode the base-2 log of the page size.

              To employ /proc/[pid]/pagemap efficiently, use /proc/[pid]/maps to determine which areas of memory
              are actually mapped and seek to skip over unmapped regions.

              The /proc/[pid]/pagemap file is present only if the CONFIG_PROC_PAGE_MONITOR kernel  configuration
              option is enabled.

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

       /proc/[pid]/personality (since Linux 2.6.28)
              This read-only file exposes the process's execution domain, as set by personality(2).   The  value
              is displayed in hexadecimal notation.

              Permission  to  access  this  file  is governed by a ptrace access mode PTRACE_MODE_ATTACH_FSCREDS
              check; see ptrace(2).

       /proc/[pid]/root
              UNIX and Linux support the idea of a per-process root of the  filesystem,  set  by  the  chroot(2)
              system  call.   This  file  is  a  symbolic  link that points to the process's root directory, and
              behaves in the same way as exe, and fd/*.

              Note however that this file is not merely a symbolic link.  It  provides  the  same  view  of  the
              filesystem  (including  namespaces  and  the set of per-process mounts) as the process itself.  An
              example illustrates this point.  In one  terminal,  we  start  a  shell  in  new  user  and  mount
              namespaces, and in that shell we create some new mount points:

                  $ PS1='sh1# ' unshare -Urnm
                  sh1# mount -t tmpfs tmpfs /etc  # Mount empty tmpfs at /etc
                  sh1# mount --bind /usr /dev     # Mount /usr at /dev
                  sh1# echo $$
                  27123

              In  a  second  terminal  window,  in  the  initial mount namespace, we look at the contents of the
              corresponding mounts in the initial and new namespaces:

                  $ PS1='sh2# ' sudo sh
                  sh2# ls /etc | wc -l                  # In initial NS
                  309
                  sh2# ls /proc/27123/root/etc | wc -l  # /etc in other NS
                  0                                     # The empty tmpfs dir
                  sh2# ls /dev | wc -l                  # In initial NS
                  205
                  sh2# ls /proc/27123/root/dev | wc -l  # /dev in other NS
                  11                                    # Actually bind
                                                        # mounted to /usr
                  sh2# ls /usr | wc -l                  # /usr in initial NS
                  11

              In a multithreaded process, the contents of the /proc/[pid]/root symbolic link are  not  available
              if the main thread has already terminated (typically by calling pthread_exit(3)).

              Permission  to dereference or read (readlink(2)) this symbolic link is governed by a ptrace access
              mode PTRACE_MODE_READ_FSCREDS check; see ptrace(2).

       /proc/[pid]/seccomp (Linux 2.6.12 to 2.6.22)
              This file can be used to read and change the process's secure computing  (seccomp)  mode  setting.
              It  contains  the value 0 if the process is not in seccomp mode, and 1 if the process is in strict
              seccomp mode (see seccomp(2)).  Writing 1 to this file places the process irreversibly  in  strict
              seccomp mode.  (Further attempts to write to the file fail with the EPERM error.)

              In  Linux  2.6.23,  this  file  went  away,  to  be  replaced  by  the prctl(2) PR_GET_SECCOMP and
              PR_SET_SECCOMP operations (and later by seccomp(2) and the Seccomp field in /proc/[pid]/status).

       /proc/[pid]/setgroups (since Linux 3.19)
              See user_namespaces(7).

       /proc/[pid]/smaps (since Linux 2.6.14)
              This file shows memory consumption for each of  the  process's  mappings.   (The  pmap(1)  command
              displays  similar  information, in a form that may be easier for parsing.)  For each mapping there
              is a series of lines such as the following:

                  00400000-0048a000 r-xp 00000000 fd:03 960637       /bin/bash
                  Size:                552 kB
                  Rss:                 460 kB
                  Pss:                 100 kB
                  Shared_Clean:        452 kB
                  Shared_Dirty:          0 kB
                  Private_Clean:         8 kB
                  Private_Dirty:         0 kB
                  Referenced:          460 kB
                  Anonymous:             0 kB
                  AnonHugePages:         0 kB
                  ShmemHugePages:        0 kB
                  ShmemPmdMapped:        0 kB
                  Swap:                  0 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  Locked:                0 kB
                  ProtectionKey:         0
                  VmFlags: rd ex mr mw me dw

              The first of these  lines  shows  the  same  information  as  is  displayed  for  the  mapping  in
              /proc/[pid]/maps.   The  following  lines  show the size of the mapping, the amount of the mapping
              that is currently resident in RAM ("Rss"),  the  process's  proportional  share  of  this  mapping
              ("Pss"),  the  number  of clean and dirty shared pages in the mapping, and the number of clean and
              dirty private pages in the mapping.  "Referenced" indicates the amount of memory currently  marked
              as  referenced  or  accessed.   "Anonymous" shows the amount of memory that does not belong to any
              file.  "Swap" shows how much would-be-anonymous memory is also used, but out on swap.

              The "KernelPageSize" line (available since Linux 2.6.29) is the page size used by  the  kernel  to
              back  the  virtual  memory  area.  This matches the size used by the MMU in the majority of cases.
              However, one counter-example occurs on PPC64 kernels whereby a kernel using 64kB as  a  base  page
              size  may still use 4kB pages for the MMU on older processors.  To distinguish the two attributes,
              the "MMUPageSize" line (also available since Linux 2.6.29) reports the page size used by the MMU.

              The "Locked" indicates whether the mapping is locked in memory or not.

              The "ProtectionKey" line (available since Linux 4.9, on x86 only) contains the  memory  protection
              key  (see  pkeys(7))  associated  with the virtual memory area.  This entry is present only if the
              kernel was built with the CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS configuration option.

              The "VmFlags" line (available since Linux 3.8) represents the kernel  flags  associated  with  the
              virtual memory area, encoded using the following two-letter codes:

                  rd  - readable
                  wr  - writable
                  ex  - executable
                  sh  - shared
                  mr  - may read
                  mw  - may write
                  me  - may execute
                  ms  - may share
                  gd  - stack segment grows down
                  pf  - pure PFN range
                  dw  - disabled write to the mapped file
                  lo  - pages are locked in memory
                  io  - memory mapped I/O area
                  sr  - sequential read advise provided
                  rr  - random read advise provided
                  dc  - do not copy area on fork
                  de  - do not expand area on remapping
                  ac  - area is accountable
                  nr  - swap space is not reserved for the area
                  ht  - area uses huge tlb pages
                  nl  - non-linear mapping
                  ar  - architecture specific flag
                  dd  - do not include area into core dump
                  sd  - soft-dirty flag
                  mm  - mixed map area
                  hg  - huge page advise flag
                  nh  - no-huge page advise flag
                  mg  - mergeable advise flag

              "ProtectionKey"  field  contains  the  memory  protection  key  (see pkeys(5)) associated with the
              virtual   memory   area.     Present    only    if    the    kernel    was    built    with    the
              CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS configuration option. (since Linux 4.6)

              The  /proc/[pid]/smaps  file  is present only if the CONFIG_PROC_PAGE_MONITOR kernel configuration
              option is enabled.

       /proc/[pid]/stack (since Linux 2.6.29)
              This file provides a symbolic trace of the function calls in this process's  kernel  stack.   This
              file is provided only if the kernel was built with the CONFIG_STACKTRACE configuration option.

              Permission  to  access  this  file  is governed by a ptrace access mode PTRACE_MODE_ATTACH_FSCREDS
              check; see ptrace(2).

       /proc/[pid]/stat
              Status information about the process.  This is used by ps(1).  It is defined in the kernel  source
              file fs/proc/array.c.

              The  fields, in order, with their proper scanf(3) format specifiers, are listed below.  Whether or
              not certain of these fields display  valid  information  is  governed  by  a  ptrace  access  mode
              PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT  check  (refer  to ptrace(2)).  If the check denies
              access, then the field value is displayed as 0.   The  affected  fields  are  indicated  with  the
              marking [PT].

              (1) pid  %d
                        The process ID.

              (2) comm  %s
                        The  filename  of  the  executable,  in parentheses.  This is visible whether or not the
                        executable is swapped out.

              (3) state  %c
                        One of the following characters, indicating process state:

                        R  Running

                        S  Sleeping in an interruptible wait

                        D  Waiting in uninterruptible disk sleep

                        Z  Zombie

                        T  Stopped (on a signal) or (before Linux 2.6.33) trace stopped

                        t  Tracing stop (Linux 2.6.33 onward)

                        W  Paging (only before Linux 2.6.0)

                        X  Dead (from Linux 2.6.0 onward)

                        x  Dead (Linux 2.6.33 to 3.13 only)

                        K  Wakekill (Linux 2.6.33 to 3.13 only)

                        W  Waking (Linux 2.6.33 to 3.13 only)

                        P  Parked (Linux 3.9 to 3.13 only)

              (4) ppid  %d
                        The PID of the parent of this process.

              (5) pgrp  %d
                        The process group ID of the process.

              (6) session  %d
                        The session ID of the process.

              (7) tty_nr  %d
                        The controlling terminal of the process.  (The minor device number is contained  in  the
                        combination of bits 31 to 20 and 7 to 0; the major device number is in bits 15 to 8.)

              (8) tpgid  %d
                        The ID of the foreground process group of the controlling terminal of the process.

              (9) flags  %u
                        The  kernel  flags  word  of the process.  For bit meanings, see the PF_* defines in the
                        Linux kernel source file include/linux/sched.h.  Details depend on the kernel version.

                        The format for this field was %lu before Linux 2.6.

              (10) minflt  %lu
                        The number of minor faults the process has made which have not required loading a memory
                        page from disk.

              (11) cminflt  %lu
                        The number of minor faults that the process's waited-for children have made.

              (12) majflt  %lu
                        The  number  of  major  faults the process has made which have required loading a memory
                        page from disk.

              (13) cmajflt  %lu
                        The number of major faults that the process's waited-for children have made.

              (14) utime  %lu
                        Amount of time that this process has been scheduled in  user  mode,  measured  in  clock
                        ticks  (divide  by  sysconf(_SC_CLK_TCK)).   This  includes guest time, guest_time (time
                        spent running a virtual CPU, see below), so that applications that are not aware of  the
                        guest time field do not lose that time from their calculations.

              (15) stime  %lu
                        Amount  of  time  that this process has been scheduled in kernel mode, measured in clock
                        ticks (divide by sysconf(_SC_CLK_TCK)).

              (16) cutime  %ld
                        Amount of time that this process's waited-for children have been scheduled in user mode,
                        measured  in  clock  ticks (divide by sysconf(_SC_CLK_TCK)).  (See also times(2).)  This
                        includes guest time, cguest_time (time spent running a virtual CPU, see below).

              (17) cstime  %ld
                        Amount of time that this process's waited-for children have  been  scheduled  in  kernel
                        mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (18) priority  %ld
                        (Explanation  for Linux 2.6) For processes running a real-time scheduling policy (policy
                        below; see sched_setscheduler(2)), this is the negated scheduling priority,  minus  one;
                        that  is,  a  number in the range -2 to -100, corresponding to real-time priorities 1 to
                        99.  For processes running under a non-real-time scheduling policy, this is the raw nice
                        value  (setpriority(2))  as represented in the kernel.  The kernel stores nice values as
                        numbers in the range 0 (high) to 39 (low), corresponding to the user-visible nice  range
                        of -20 to 19.

                        Before Linux 2.6, this was a scaled value based on the scheduler weighting given to this
                        process.

              (19) nice  %ld
                        The nice value (see setpriority(2)), a value in the range 19 (low priority) to -20 (high
                        priority).

              (20) num_threads  %ld
                        Number  of threads in this process (since Linux 2.6).  Before kernel 2.6, this field was
                        hard coded to 0 as a placeholder for an earlier removed field.

              (21) itrealvalue  %ld
                        The time in jiffies before the next SIGALRM is sent to the process due  to  an  interval
                        timer.  Since kernel 2.6.17, this field is no longer maintained, and is hard coded as 0.

              (22) starttime  %llu
                        The time the process started after system boot.  In kernels before Linux 2.6, this value
                        was expressed in jiffies.  Since Linux 2.6,  the  value  is  expressed  in  clock  ticks
                        (divide by sysconf(_SC_CLK_TCK)).

                        The format for this field was %lu before Linux 2.6.

              (23) vsize  %lu
                        Virtual memory size in bytes.

              (24) rss  %ld
                        Resident  Set  Size:  number  of pages the process has in real memory.  This is just the
                        pages which count toward text, data, or stack space.  This does not include pages  which
                        have not been demand-loaded in, or which are swapped out.

              (25) rsslim  %lu
                        Current soft limit in bytes on the rss of the process; see the description of RLIMIT_RSS
                        in getrlimit(2).

              (26) startcode  %lu  [PT]
                        The address above which program text can run.

              (27) endcode  %lu  [PT]
                        The address below which program text can run.

              (28) startstack  %lu  [PT]
                        The address of the start (i.e., bottom) of the stack.

              (29) kstkesp  %lu  [PT]
                        The current value of ESP (stack pointer), as found in the  kernel  stack  page  for  the
                        process.

              (30) kstkeip  %lu  [PT]
                        The current EIP (instruction pointer).

              (31) signal  %lu
                        The bitmap of pending signals, displayed as a decimal number.  Obsolete, because it does
                        not provide information on real-time signals; use /proc/[pid]/status instead.

              (32) blocked  %lu
                        The bitmap of blocked signals, displayed as a decimal number.  Obsolete, because it does
                        not provide information on real-time signals; use /proc/[pid]/status instead.

              (33) sigignore  %lu
                        The bitmap of ignored signals, displayed as a decimal number.  Obsolete, because it does
                        not provide information on real-time signals; use /proc/[pid]/status instead.

              (34) sigcatch  %lu
                        The bitmap of caught signals, displayed as a decimal number.  Obsolete, because it  does
                        not provide information on real-time signals; use /proc/[pid]/status instead.

              (35) wchan  %lu  [PT]
                        This  is the "channel" in which the process is waiting.  It is the address of a location
                        in the kernel where the process is sleeping.  The corresponding  symbolic  name  can  be
                        found in /proc/[pid]/wchan.

              (36) nswap  %lu
                        Number of pages swapped (not maintained).

              (37) cnswap  %lu
                        Cumulative nswap for child processes (not maintained).

              (38) exit_signal  %d  (since Linux 2.1.22)
                        Signal to be sent to parent when we die.

              (39) processor  %d  (since Linux 2.2.8)
                        CPU number last executed on.

              (40) rt_priority  %u  (since Linux 2.5.19)
                        Real-time  scheduling  priority,  a  number in the range 1 to 99 for processes scheduled
                        under a real-time policy, or 0, for non-real-time processes (see sched_setscheduler(2)).

              (41) policy  %u  (since Linux 2.5.19)
                        Scheduling policy (see sched_setscheduler(2)).  Decode using the  SCHED_*  constants  in
                        linux/sched.h.

                        The format for this field was %lu before Linux 2.6.22.

              (42) delayacct_blkio_ticks  %llu  (since Linux 2.6.18)
                        Aggregated block I/O delays, measured in clock ticks (centiseconds).

              (43) guest_time  %lu  (since Linux 2.6.24)
                        Guest  time  of  the  process  (time  spent  running a virtual CPU for a guest operating
                        system), measured in clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (44) cguest_time  %ld  (since Linux 2.6.24)
                        Guest  time  of  the  process's  children,  measured   in   clock   ticks   (divide   by
                        sysconf(_SC_CLK_TCK)).

              (45) start_data  %lu  (since Linux 3.3)  [PT]
                        Address above which program initialized and uninitialized (BSS) data are placed.

              (46) end_data  %lu  (since Linux 3.3)  [PT]
                        Address below which program initialized and uninitialized (BSS) data are placed.

              (47) start_brk  %lu  (since Linux 3.3)  [PT]
                        Address above which program heap can be expanded with brk(2).

              (48) arg_start  %lu  (since Linux 3.5)  [PT]
                        Address above which program command-line arguments (argv) are placed.

              (49) arg_end  %lu  (since Linux 3.5)  [PT]
                        Address below program command-line arguments (argv) are placed.

              (50) env_start  %lu  (since Linux 3.5)  [PT]
                        Address above which program environment is placed.

              (51) env_end  %lu  (since Linux 3.5)  [PT]
                        Address below which program environment is placed.

              (52) exit_code  %d  (since Linux 3.5)  [PT]
                        The thread's exit status in the form reported by waitpid(2).

       /proc/[pid]/statm
              Provides information about memory usage, measured in pages.  The columns are:

                  size       (1) total program size
                             (same as VmSize in /proc/[pid]/status)
                  resident   (2) resident set size
                             (same as VmRSS in /proc/[pid]/status)
                  shared     (3) number of resident shared pages (i.e., backed by a file)
                             (same as RssFile+RssShmem in /proc/[pid]/status)
                  text       (4) text (code)
                  lib        (5) library (unused since Linux 2.6; always 0)
                  data       (6) data + stack
                  dt         (7) dirty pages (unused since Linux 2.6; always 0)

       /proc/[pid]/status
              Provides  much  of  the  information  in /proc/[pid]/stat and /proc/[pid]/statm in a format that's
              easier for humans to parse.  Here's an example:

                  $ cat /proc/$$/status
                  Name:   bash
                  Umask:  0022
                  State:  S (sleeping)
                  Tgid:   17248
                  Ngid:   0
                  Pid:    17248
                  PPid:   17200
                  TracerPid:      0
                  Uid:    1000    1000    1000    1000
                  Gid:    100     100     100     100
                  FDSize: 256
                  Groups: 16 33 100
                  NStgid: 17248
                  NSpid:  17248
                  NSpgid: 17248
                  NSsid:  17200
                  VmPeak:     131168 kB
                  VmSize:     131168 kB
                  VmLck:           0 kB
                  VmPin:           0 kB
                  VmHWM:       13484 kB
                  VmRSS:       13484 kB
                  RssAnon:     10264 kB
                  RssFile:      3220 kB
                  RssShmem:        0 kB
                  VmData:      10332 kB
                  VmStk:         136 kB
                  VmExe:         992 kB
                  VmLib:        2104 kB
                  VmPTE:          76 kB
                  VmPMD:          12 kB
                  VmSwap:          0 kB
                  HugetlbPages:          0 kB        # 4.4
                  Threads:        1
                  SigQ:   0/3067
                  SigPnd: 0000000000000000
                  ShdPnd: 0000000000000000
                  SigBlk: 0000000000010000
                  SigIgn: 0000000000384004
                  SigCgt: 000000004b813efb
                  CapInh: 0000000000000000
                  CapPrm: 0000000000000000
                  CapEff: 0000000000000000
                  CapBnd: ffffffffffffffff
                  CapAmb:   0000000000000000
                  NoNewPrivs:     0
                  Seccomp:        0
                  Cpus_allowed:   00000001
                  Cpus_allowed_list:      0
                  Mems_allowed:   1
                  Mems_allowed_list:      0
                  voluntary_ctxt_switches:        150
                  nonvoluntary_ctxt_switches:     545

              The fields are as follows:

              * Name: Command run by this process.

              * Umask: Process umask, expressed in octal with a leading zero; see umask(2).  (Since Linux 4.7.)

              * State: Current state of the process.  One of "R (running)", "S (sleeping)", "D (disk sleep)", "T
                (stopped)", "T (tracing stop)", "Z (zombie)", or "X (dead)".

              * Tgid: Thread group ID (i.e., Process ID).

              * Ngid: NUMA group ID (0 if none; since Linux 3.13).

              * Pid: Thread ID (see gettid(2)).

              * PPid: PID of parent process.

              * TracerPid: PID of process tracing this process (0 if not being traced).

              * Uid, Gid: Real, effective, saved set, and filesystem UIDs (GIDs).

              * FDSize: Number of file descriptor slots currently allocated.

              * Groups: Supplementary group list.

              * NStgid  :  Thread group ID (i.e., PID) in each of the PID namespaces of which [pid] is a member.
                The leftmost entry shows the value with respect to the PID namespace  of  the  reading  process,
                followed by the value in successively nested inner namespaces.  (Since Linux 4.1.)

              * NSpid:  Thread  ID  in  each  of  the PID namespaces of which [pid] is a member.  The fields are
                ordered as for NStgid.  (Since Linux 4.1.)

              * NSpgid: Process group ID in each of the PID namespaces of which [pid] is a member.   The  fields
                are ordered as for NStgid.  (Since Linux 4.1.)

              * NSsid:  descendant  namespace  session  ID hierarchy Session ID in each of the PID namespaces of
                which [pid] is a member.  The fields are ordered as for NStgid.  (Since Linux 4.1.)

              * VmPeak: Peak virtual memory size.

              * VmSize: Virtual memory size.

              * VmLck: Locked memory size (see mlock(3)).

              * VmPin: Pinned memory size (since Linux 3.2).  These  are  pages  that  can't  be  moved  because
                something needs to directly access physical memory.

              * VmHWM: Peak resident set size ("high water mark").

              * VmRSS:  Resident  set  size.   Note  that  the  value  here  is the sum of RssAnon, RssFile, and
                RssShmem.

              * RssAnon: Size of resident anonymous memory.  (since Linux 4.5).

              * RssFile: Size of resident file mappings.  (since Linux 4.5).

              * RssShmem: Size of resident shared  memory  (includes  System  V  shared  memory,  mappings  from
                tmpfs(5), and shared anonymous mappings).  (since Linux 4.5).

              * VmData, VmStk, VmExe: Size of data, stack, and text segments.

              * VmLib: Shared library code size.

              * VmPTE: Page table entries size (since Linux 2.6.10).

              * VmPMD: Size of second-level page tables (since Linux 4.0).

              * VmSwap:  Swapped-out  virtual  memory  size  by anonymous private pages; shmem swap usage is not
                included (since Linux 2.6.34).

              * HugetlbPages: Size of hugetlb memory portions.  (since Linux 4.4).

              * Threads: Number of threads in process containing this thread.

              * SigQ: This field contains two slash-separated numbers that relate to queued signals for the real
                user  ID of this process.  The first of these is the number of currently queued signals for this
                real user ID, and the second is the resource limit on the number  of  queued  signals  for  this
                process (see the description of RLIMIT_SIGPENDING in getrlimit(2)).

              * SigPnd, ShdPnd: Number of signals pending for thread and for process as a whole (see pthreads(7)
                and signal(7)).

              * SigBlk, SigIgn, SigCgt: Masks  indicating  signals  being  blocked,  ignored,  and  caught  (see
                signal(7)).

              * CapInh,  CapPrm,  CapEff: Masks of capabilities enabled in inheritable, permitted, and effective
                sets (see capabilities(7)).

              * CapBnd: Capability Bounding set (since Linux 2.6.26, see capabilities(7)).

              * CapAmb: Ambient capability set (since Linux 4.3, see capabilities(7)).

              * NoNewPrivs: Value of the no_new_privs bit (since Linux 4.10, see prctl(2)).

              * Seccomp:  Seccomp  mode  of  the  process  (since  Linux  3.8,   see   seccomp(2)).    0   means
                SECCOMP_MODE_DISABLED;  1 means SECCOMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER.  This field is
                provided only if the kernel was  built  with  the  CONFIG_SECCOMP  kernel  configuration  option
                enabled.

              * Cpus_allowed: Mask of CPUs on which this process may run (since Linux 2.6.24, see cpuset(7)).

              * Cpus_allowed_list: Same as previous, but in "list format" (since Linux 2.6.26, see cpuset(7)).

              * Mems_allowed: Mask of memory nodes allowed to this process (since Linux 2.6.24, see cpuset(7)).

              * Mems_allowed_list: Same as previous, but in "list format" (since Linux 2.6.26, see cpuset(7)).

              * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of voluntary and involuntary context
                switches (since Linux 2.6.23).

       /proc/[pid]/syscall (since Linux 2.6.27)
              This file exposes the system call number and argument registers  for  the  system  call  currently
              being  executed  by  the  process, followed by the values of the stack pointer and program counter
              registers.  The values of all six argument registers are exposed, although most system  calls  use
              fewer registers.

              If  the  process  is  blocked, but not in a system call, then the file displays -1 in place of the
              system call number, followed by just the values of the stack  pointer  and  program  counter.   If
              process is not blocked, then the file contains just the string "running".

              This file is present only if the kernel was configured with CONFIG_HAVE_ARCH_TRACEHOOK.

              Permission  to  access  this  file  is governed by a ptrace access mode PTRACE_MODE_ATTACH_FSCREDS
              check; see ptrace(2).

       /proc/[pid]/task (since Linux 2.6.0-test6)
              This is a directory that contains one subdirectory for each thread in the process.   The  name  of
              each  subdirectory  is the numerical thread ID ([tid]) of the thread (see gettid(2)).  Within each
              of these subdirectories, there is a set of files with the same names and  contents  as  under  the
              /proc/[pid]  directories.  For attributes that are shared by all threads, the contents for each of
              the files under the task/[tid] subdirectories will be the same as in the corresponding file in the
              parent  /proc/[pid]  directory  (e.g., in a multithreaded process, all of the task/[tid]/cwd files
              will have the same value as the /proc/[pid]/cwd file in the parent directory,  since  all  of  the
              threads  in  a  process  share  a  working  directory).  For attributes that are distinct for each
              thread, the corresponding files under task/[tid] may have different values (e.g.,  various  fields
              in  each of the task/[tid]/status files may be different for each thread), or they might not exist
              in /proc/[pid] at all.  In a multithreaded process, the contents of the /proc/[pid]/task directory
              are   not   available   if   the   main  thread  has  already  terminated  (typically  by  calling
              pthread_exit(3)).

       /proc/[pid]/task/[tid]/children (since Linux 3.5)
              A space-separated list of child tasks of this task.  Each child task is represented by its TID.

              This option is intended for use by the checkpoint-restore (CRIU) system, and reliably  provides  a
              list  of  children  only  if  all  of the child processes are stopped or frozen.  It does not work
              properly if children of the target task exit while the file is being read!  Exiting  children  may
              cause  non-exiting  children  to  be  omitted  from the list.  This makes this interface even more
              unreliable than classic PID-based approaches if the inspected task and its children aren't frozen,
              and most code should probably not use this interface.

              Until  Linux  4.2,  the presence of this file was governed by the CONFIG_CHECKPOINT_RESTORE kernel
              configuration option.  Since Linux 4.2, it is governed by the CONFIG_PROC_CHILDREN option.

       /proc/[pid]/timers (since Linux 3.10)
              A list of the POSIX timers for this process.  Each timer is listed with a line  that  starts  with
              the string "ID:".  For example:

                  ID: 1
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 0
                  ID: 0
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 1

              The lines shown for each timer have the following meanings:

              ID     The  ID  for this timer.  This is not the same as the timer ID returned by timer_create(2);
                     rather, it is the same kernel-internal ID that is available via the si_timerid field of the
                     siginfo_t structure (see sigaction(2)).

              signal This  is  the  signal  number  that  this timer uses to deliver notifications followed by a
                     slash, and then the sigev_value value supplied to  the  signal  handler.   Valid  only  for
                     timers that notify via a signal.

              notify The  part  before  the  slash  specifies  the  mechanism  that  this  timer uses to deliver
                     notifications, and is one of "thread", "signal",  or  "none".   Immediately  following  the
                     slash is either the string "tid" for timers with SIGEV_THREAD_ID notification, or "pid" for
                     timers that notify by other mechanisms.  Following the "." is the PID of  the  process  (or
                     the  kernel thread ID of the thread)  that will be delivered a signal if the timer delivers
                     notifications via a signal.

              ClockID
                     This field identifies the clock that the timer uses for measuring time.  For  most  clocks,
                     this is a number that matches one of the user-space CLOCK_* constants exposed via <time.h>.
                     CLOCK_PROCESS_CPUTIME_ID  timers  display   with   a   value   of   -6   in   this   field.
                     CLOCK_THREAD_CPUTIME_ID timers display with a value of -2 in this field.

              This file is available only when the kernel was configured with CONFIG_CHECKPOINT_RESTORE.

       /proc/[pid]/timerslack_ns (since Linux 4.6)
              This  file  exposes the process's "current" timer slack value, expressed in nanoseconds.  The file
              is writable, allowing the process's timer slack value to be  changed.   Writing  0  to  this  file
              resets the "current" timer slack to the "default" timer slack value.  For further details, see the
              discussion of PR_SET_TIMERSLACK in prctl(2).

              Initially,  permission  to  access  this   file   was   governed   by   a   ptrace   access   mode
              PTRACE_MODE_ATTACH_FSCREDS  check  (see  ptrace(2)).   However,  this  was subsequently deemed too
              strict a requirement (and had the side effect that requiring a process to have the  CAP_SYS_PTRACE
              capability  would  also allow it to view and change any process's memory).  Therefore, since Linux
              4.9, only the (weaker) CAP_SYS_NICE capability is required to access this file.

       /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/wchan (since Linux 2.6.0)
              The symbolic name corresponding to the location in the kernel where the process is sleeping.

              Permission to access this file is governed by a ptrace access mode PTRACE_MODE_READ_FSCREDS check;
              see ptrace(2).

       /proc/apm
              Advanced  power  management  version  and battery information when CONFIG_APM is defined at kernel
              compilation time.

       /proc/buddyinfo
              This file contains information which is used for diagnosing  memory  fragmentation  issues.   Each
              line starts with the identification of the node and the name of the zone which together identify a
              memory region This is then followed by the count of available chunks of a certain order  in  which
              these zones are split.  The size in bytes of a certain order is given by the formula:

                  (2^order) * PAGE_SIZE

              The  binary  buddy allocator algorithm inside the kernel will split one chunk into two chunks of a
              smaller order (thus with half the size) or combine two contiguous chunks into one larger chunk  of
              a  higher  order  (thus with double the size) to satisfy allocation requests and to counter memory
              fragmentation.  The order matches the column number, when starting to count at zero.

              For example on an x86-64 system:

  Node 0, zone     DMA     1    1    1    0    2    1    1    0    1    1    3
  Node 0, zone   DMA32    65   47    4   81   52   28   13   10    5    1  404
  Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587

              In this example, there is one node containing three zones and there are 11 different chunk  sizes.
              If  the  page size is 4 kilobytes, then the first zone called DMA (on x86 the first 16 megabyte of
              memory) has 1 chunk of 4 kilobytes (order 0) available and has 3 chunks of 4 megabytes (order  10)
              available.

              If  the  memory  is  heavily  fragmented,  the  counters  for higher order chunks will be zero and
              allocation of large contiguous areas will fail.

              Further information about the zones can be found in /proc/zoneinfo.

       /proc/bus
              Contains subdirectories for installed busses.

       /proc/bus/pccard
              Subdirectory for PCMCIA devices when CONFIG_PCMCIA is set at kernel compilation time.

       /proc/bus/pccard/drivers

       /proc/bus/pci
              Contains various bus subdirectories and pseudo-files  containing  information  about  PCI  busses,
              installed devices, and device drivers.  Some of these files are not ASCII.

       /proc/bus/pci/devices
              Information about PCI devices.  They may be accessed through lspci(8) and setpci(8).

       /proc/cgroups (since Linux 2.6.24)
              See cgroups(7).

       /proc/cmdline
              Arguments  passed to the Linux kernel at boot time.  Often done via a boot manager such as lilo(8)
              or grub(8).

       /proc/config.gz (since Linux 2.6)
              This file exposes the configuration options that were used to build the currently running  kernel,
              in  the  same format as they would be shown in the .config file that resulted when configuring the
              kernel (using make xconfig, make config, or similar).  The file contents are compressed;  view  or
              search  them  using  zcat(1)  and zgrep(1).  As long as no changes have been made to the following
              file, the contents of /proc/config.gz are the same as those provided by:

                  cat /lib/modules/$(uname -r)/build/.config

              /proc/config.gz is provided only if the kernel is configured with CONFIG_IKCONFIG_PROC.

       /proc/crypto
              A list of the ciphers provided by the kernel crypto API.  For details, see the kernel Linux Kernel
              Crypto  API  documentation  available  under the kernel source directory Documentation/crypto/ (or
              Documentation/DocBook before 4.10; the documentation can be built using a  command  such  as  make
              htmldocs in the root directory of the kernel source tree).

       /proc/cpuinfo
              This  is  a  collection  of  CPU  and  system  architecture  dependent  items,  for each supported
              architecture a different list.  Two common entries  are  processor  which  gives  CPU  number  and
              bogomips;  a  system  constant that is calculated during kernel initialization.  SMP machines have
              information for each CPU.  The lscpu(1) command gathers its information from this file.

       /proc/devices
              Text listing of major numbers and device  groups.   This  can  be  used  by  MAKEDEV  scripts  for
              consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
              This  file  contains  disk  I/O statistics for each disk device.  See the Linux kernel source file
              Documentation/iostats.txt for further information.

       /proc/dma
              This is a list of the registered ISA DMA (direct memory access) channels in use.

       /proc/driver
              Empty subdirectory.

       /proc/execdomains
              List of the execution domains (ABI personalities).

       /proc/fb
              Frame buffer information when CONFIG_FB is defined during kernel compilation.

       /proc/filesystems
              A text listing of the filesystems which are supported by the kernel, namely filesystems which were
              compiled into the kernel or whose kernel modules are currently loaded.  (See also filesystems(5).)
              If a filesystem is marked with "nodev", this means that it does not require a block device  to  be
              mounted (e.g., virtual filesystem, network filesystem).

              Incidentally,  this  file  may  be  used by mount(8) when no filesystem is specified and it didn't
              manage to determine the filesystem type.  Then  filesystems  contained  in  this  file  are  tried
              (excepted those that are marked with "nodev").

       /proc/fs
              Contains  subdirectories  that  in  turn  contain  files  with information about (certain) mounted
              filesystems.

       /proc/ide
              This directory exists on systems with the IDE bus.  There are directories for each IDE channel and
              attached device.  Files include:

                  cache              buffer size in KB
                  capacity           number of sectors
                  driver             driver version
                  geometry           physical and logical geometry
                  identify           in hexadecimal
                  media              media type
                  model              manufacturer's model number
                  settings           drive settings
                  smart_thresholds   in hexadecimal
                  smart_values       in hexadecimal

              The hdparm(8) utility provides access to this information in a friendly format.

       /proc/interrupts
              This  is  used  to record the number of interrupts per CPU per IO device.  Since Linux 2.6.24, for
              the i386 and x86-64 architectures, at least, this also includes interrupts internal to the  system
              (that  is,  not associated with a device as such), such as NMI (nonmaskable interrupt), LOC (local
              timer interrupt), and for SMP systems, TLB (TLB flush interrupt),  RES  (rescheduling  interrupt),
              CAL  (remote function call interrupt), and possibly others.  Very easy to read formatting, done in
              ASCII.

       /proc/iomem
              I/O memory map in Linux 2.4.

       /proc/ioports
              This is a list of currently registered Input-Output port regions that are in use.

       /proc/kallsyms (since Linux 2.5.71)
              This holds the kernel exported symbol definitions used by the modules(X) tools to dynamically link
              and  bind  loadable  modules.  In Linux 2.5.47 and earlier, a similar file with slightly different
              syntax was named ksyms.

       /proc/kcore
              This file represents the physical memory of the system and is stored in the ELF core file  format.
              With  this  pseudo-file, and an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be used
              to examine the current state of any kernel data structures.

              The total length of the file is the size of physical memory (RAM) plus 4 KiB.

       /proc/keys (since Linux 2.6.10)
              See keyrings(7).

       /proc/key-users (since Linux 2.6.10)
              See keyrings(7).

       /proc/kmsg
              This file can be used instead of the syslog(2) system call to read  kernel  messages.   A  process
              must  have  superuser  privileges  to  read this file, and only one process should read this file.
              This file should not be read if a syslog process is running which uses the syslog(2)  system  call
              facility to log kernel messages.

              Information in this file is retrieved with the dmesg(1) program.

       /proc/kpagecgroup (since Linux 4.3)
              This  file contains a 64-bit inode number of the memory cgroup each page is charged to, indexed by
              page frame number (see the discussion of /proc/[pid]/pagemap).

              The /proc/kpagecgroup file is present only if the  CONFIG_MEMCG  kernel  configuration  option  is
              enabled.

       /proc/kpagecount (since Linux 2.6.25)
              This  file  contains  a  64-bit  count  of the number of times each physical page frame is mapped,
              indexed by page frame number (see the discussion of /proc/[pid]/pagemap).

              The /proc/kpagecount file is present only if  the  CONFIG_PROC_PAGE_MONITOR  kernel  configuration
              option is enabled.

       /proc/kpageflags (since Linux 2.6.25)
              This  file  contains 64-bit masks corresponding to each physical page frame; it is indexed by page
              frame number (see the discussion of /proc/[pid]/pagemap).  The bits are as follows:

                   0 - KPF_LOCKED
                   1 - KPF_ERROR
                   2 - KPF_REFERENCED
                   3 - KPF_UPTODATE
                   4 - KPF_DIRTY
                   5 - KPF_LRU
                   6 - KPF_ACTIVE
                   7 - KPF_SLAB
                   8 - KPF_WRITEBACK
                   9 - KPF_RECLAIM
                  10 - KPF_BUDDY
                  11 - KPF_MMAP           (since Linux 2.6.31)
                  12 - KPF_ANON           (since Linux 2.6.31)
                  13 - KPF_SWAPCACHE      (since Linux 2.6.31)
                  14 - KPF_SWAPBACKED     (since Linux 2.6.31)
                  15 - KPF_COMPOUND_HEAD  (since Linux 2.6.31)
                  16 - KPF_COMPOUND_TAIL  (since Linux 2.6.31)
                  17 - KPF_HUGE           (since Linux 2.6.31)
                  18 - KPF_UNEVICTABLE    (since Linux 2.6.31)
                  19 - KPF_HWPOISON       (since Linux 2.6.31)
                  20 - KPF_NOPAGE         (since Linux 2.6.31)
                  21 - KPF_KSM            (since Linux 2.6.32)
                  22 - KPF_THP            (since Linux 3.4)
                  23 - KPF_BALLOON        (since Linux 3.18)
                  24 - KPF_ZERO_PAGE      (since Linux 4.0)
                  25 - KPF_IDLE           (since Linux 4.3)

              For  further  details  on  the  meanings   of   these   bits,   see   the   kernel   source   file
              Documentation/vm/pagemap.txt.   Before  kernel  2.6.29, KPF_WRITEBACK, KPF_RECLAIM, KPF_BUDDY, and
              KPF_LOCKED did not report correctly.

              The /proc/kpageflags file is present only if  the  CONFIG_PROC_PAGE_MONITOR  kernel  configuration
              option is enabled.

       /proc/ksyms (Linux 1.1.23–2.5.47)
              See /proc/kallsyms.

       /proc/loadavg
              The  first three fields in this file are load average figures giving the number of jobs in the run
              queue (state R) or waiting for disk I/O (state D) averaged over 1, 5, and 15  minutes.   They  are
              the  same  as  the  load  average numbers given by uptime(1) and other programs.  The fourth field
              consists of two numbers separated by a slash (/).  The first of these is the number  of  currently
              runnable kernel scheduling entities (processes, threads).  The value after the slash is the number
              of kernel scheduling entities that currently exist on the system.  The fifth field is the  PID  of
              the process that was most recently created on the system.

       /proc/locks
              This file shows current file locks (flock(2) and fcntl(2)) and leases (fcntl(2)).

              An example of the content shown in this file is the following:

                  1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128
                  2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF
                  3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF
                  4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF
                  5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0
                  6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1
                  7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335
                  8: OFDLCK ADVISORY  WRITE -1 08:01:8713209 128 191

              The fields shown in each line are as follows:

              (1) The ordinal position of the lock in the list.

              (2) The lock type.  Values that may appear here include:

                  FLOCK  This is a BSD file lock created using flock(2).

                  OFDLCK This is an open file description (OFD) lock created using fcntl(2).

                  POSIX  This is a POSIX byte-range lock created using fcntl(2).

              (3) Among the strings that can appear here are the following:

                  ADVISORY
                         This is an advisory lock.

                  MANDATORY
                         This is a mandatory lock.

              (4) The type of lock.  Values that can appear here are:

                  READ   This is a POSIX or OFD read lock, or a BSD shared lock.

                  WRITE  This is a POSIX or OFD write lock, or a BSD exclusive lock.

              (5) The PID of the process that owns the lock.

                  Because  OFD  locks  are not owned by a single process (since multiple processes may have file
                  descriptors that refer to the same open file description), the value -1 is displayed  in  this
                  field  for  OFD  locks.   (Before  kernel  4.14,  a bug meant that the PID of the process that
                  initially acquired the lock was displayed instead of the value -1.)

              (6) Three colon-separated subfields that identify the major and minor  device  ID  of  the  device
                  containing  the  filesystem where the locked file resides, followed by the inode number of the
                  locked file.

              (7) The byte offset of the first byte of the lock.  For BSD locks, this value is always 0.

              (8) The byte offset of the last byte of the lock.  EOF in this field means that the  lock  extends
                  to the end of the file.  For BSD locks, the value shown is always EOF.

              Since Linux 4.9, the list of locks shown in /proc/locks is filtered to show just the locks for the
              processes in the PID namespace (see pid_namespaces(7)) for which the /proc filesystem was mounted.
              (In the initial PID namespace, there is no filtering of the records shown in this file.)

              The lslocks(8) command provides a bit more information about each lock.

       /proc/malloc (only up to and including Linux 2.2)
              This file is present only if CONFIG_DEBUG_MALLOC was defined during compilation.

       /proc/meminfo
              This  file  reports  statistics about memory usage on the system.  It is used by free(1) to report
              the amount of free and used memory (both physical and swap) on the system as well  as  the  shared
              memory  and  buffers  used  by  the  kernel.   Each line of the file consists of a parameter name,
              followed by a colon, the value of the parameter, and an option unit of measurement  (e.g.,  "kB").
              The  list  below describes the parameter names and the format specifier required to read the field
              value.  Except as noted below, all of the fields have been present since  at  least  Linux  2.6.0.
              Some  fields  are  displayed  only  if  the  kernel  was  configured  with  various options; those
              dependencies are noted in the list.

              MemTotal %lu
                     Total usable RAM (i.e., physical RAM minus a few reserved bits and the kernel binary code).

              MemFree %lu
                     The sum of LowFree+HighFree.

              MemAvailable %lu (since Linux 3.14)
                     An estimate of how  much  memory  is  available  for  starting  new  applications,  without
                     swapping.

              Buffers %lu
                     Relatively  temporary  storage  for  raw  disk blocks that shouldn't get tremendously large
                     (20MB or so).

              Cached %lu
                     In-memory cache for files read from the disk (the page cache).  Doesn't include SwapCached.

              SwapCached %lu
                     Memory that once was swapped out, is swapped back in but still also is in  the  swap  file.
                     (If  memory  pressure  is high, these pages don't need to be swapped out again because they
                     are already in the swap file.  This saves I/O.)

              Active %lu
                     Memory that has been used  more  recently  and  usually  not  reclaimed  unless  absolutely
                     necessary.

              Inactive %lu
                     Memory  which  has  been less recently used.  It is more eligible to be reclaimed for other
                     purposes.

              Active(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Active(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Unevictable %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was required.)  [To be documented.]

              Mlocked %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was required.)  [To be documented.]

              HighTotal %lu
                     (Starting with Linux  2.6.19,  CONFIG_HIGHMEM  is  required.)   Total  amount  of  highmem.
                     Highmem  is all memory above ~860MB of physical memory.  Highmem areas are for use by user-
                     space programs, or for the page cache.  The kernel must use tricks to access  this  memory,
                     making it slower to access than lowmem.

              HighFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)  Amount of free highmem.

              LowTotal %lu
                     (Starting  with Linux 2.6.19, CONFIG_HIGHMEM is required.)  Total amount of lowmem.  Lowmem
                     is memory which can be used for everything that highmem can be used for,  but  it  is  also
                     available for the kernel's use for its own data structures.  Among many other things, it is
                     where everything from Slab is allocated.  Bad things happen when you're out of lowmem.

              LowFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)  Amount of free lowmem.

              MmapCopy %lu (since Linux 2.6.29)
                     (CONFIG_MMU is required.)  [To be documented.]

              SwapTotal %lu
                     Total amount of swap space available.

              SwapFree %lu
                     Amount of swap space that is currently unused.

              Dirty %lu
                     Memory which is waiting to get written back to the disk.

              Writeback %lu
                     Memory which is actively being written back to the disk.

              AnonPages %lu (since Linux 2.6.18)
                     Non-file backed pages mapped into user-space page tables.

              Mapped %lu
                     Files which have been mapped into memory (with mmap(2)), such as libraries.

              Shmem %lu (since Linux 2.6.32)
                     Amount of memory consumed in tmpfs(5) filesystems.

              Slab %lu
                     In-kernel data structures cache.  (See slabinfo(5).)

              SReclaimable %lu (since Linux 2.6.19)
                     Part of Slab, that might be reclaimed, such as caches.

              SUnreclaim %lu (since Linux 2.6.19)
                     Part of Slab, that cannot be reclaimed on memory pressure.

              KernelStack %lu (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              PageTables %lu (since Linux 2.6.18)
                     Amount of memory dedicated to the lowest level of page tables.

              Quicklists %lu (since Linux 2.6.27)
                     (CONFIG_QUICKLIST is required.)  [To be documented.]

              NFS_Unstable %lu (since Linux 2.6.18)
                     NFS pages sent to the server, but not yet committed to stable storage.

              Bounce %lu (since Linux 2.6.18)
                     Memory used for block device "bounce buffers".

              WritebackTmp %lu (since Linux 2.6.26)
                     Memory used by FUSE for temporary writeback buffers.

              CommitLimit %lu (since Linux 2.6.10)
                     This is the total amount of memory currently available  to  be  allocated  on  the  system,
                     expressed  in  kilobytes.  This limit is adhered to only if strict overcommit accounting is
                     enabled (mode 2 in /proc/sys/vm/overcommit_memory).  The limit is calculated  according  to
                     the  formula  described under /proc/sys/vm/overcommit_memory.  For further details, see the
                     kernel source file Documentation/vm/overcommit-accounting.

              Committed_AS %lu
                     The amount of memory presently allocated on the system.  The committed memory is a  sum  of
                     all  of the memory which has been allocated by processes, even if it has not been "used" by
                     them as of yet.  A process which allocates 1GB of memory (using malloc(3) or similar),  but
                     touches only 300MB of that memory will show up as using only 300MB of memory even if it has
                     the address space allocated for the entire 1GB.

                     This 1GB is memory which has been "committed" to by the VM and can be used at any  time  by
                     the  allocating  application.   With  strict  overcommit  enabled  on the system (mode 2 in
                     /proc/sys/vm/overcommit_memory), allocations which would exceed the CommitLimit will not be
                     permitted.   This  is  useful if one needs to guarantee that processes will not fail due to
                     lack of memory once that memory has been successfully allocated.

              VmallocTotal %lu
                     Total size of vmalloc memory area.

              VmallocUsed %lu
                     Amount of vmalloc area which is used.

              VmallocChunk %lu
                     Largest contiguous block of vmalloc area which is free.

              HardwareCorrupted %lu (since Linux 2.6.32)
                     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]

              AnonHugePages %lu (since Linux 2.6.38)
                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)  Non-file backed huge pages  mapped  into  user-
                     space page tables.

              ShmemHugePages %lu (since Linux 4.8)
                     (CONFIG_TRANSPARENT_HUGEPAGE  is  required.)   Memory  used  by  shared  memory (shmem) and
                     tmpfs(5) allocated with huge pages

              ShmemPmdMapped %lu (since Linux 4.8)
                     (CONFIG_TRANSPARENT_HUGEPAGE is required.)  Shared memory mapped into user space with  huge
                     pages.

              CmaTotal %lu (since Linux 3.1)
                     Total CMA (Contiguous Memory Allocator) pages.  (CONFIG_CMA is required.)

              CmaFree %lu (since Linux 3.1)
                     Free CMA (Contiguous Memory Allocator) pages.  (CONFIG_CMA is required.)

              HugePages_Total %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of the pool of huge pages.

              HugePages_Free %lu
                     (CONFIG_HUGETLB_PAGE  is  required.)  The number of huge pages in the pool that are not yet
                     allocated.

              HugePages_Rsvd %lu (since Linux 2.6.17)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of huge pages for which a commitment
                     to  allocate  from  the  pool  has  been  made, but no allocation has yet been made.  These
                     reserved huge pages guarantee that an application will be able to allocate a huge page from
                     the pool of huge pages at fault time.

              HugePages_Surp %lu (since Linux 2.6.24)
                     (CONFIG_HUGETLB_PAGE  is required.)  This is the number of huge pages in the pool above the
                     value in /proc/sys/vm/nr_hugepages.  The maximum number of surplus huge pages is controlled
                     by /proc/sys/vm/nr_overcommit_hugepages.

              Hugepagesize %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of huge pages.

              DirectMap4k %lu (since Linux 2.6.27)
                     Number of bytes of RAM linearly mapped by kernel in 4kB pages.  (x86.)

              DirectMap4M %lu (since Linux 2.6.27)
                     Number  of bytes of RAM linearly mapped by kernel in 4MB pages.  (x86 with CONFIG_X86_64 or
                     CONFIG_X86_PAE enabled.)

              DirectMap2M %lu (since Linux 2.6.27)
                     Number of bytes of RAM  linearly  mapped  by  kernel  in  2MB  pages.   (x86  with  neither
                     CONFIG_X86_64 nor CONFIG_X86_PAE enabled.)

              DirectMap1G %lu (since Linux 2.6.27)
                     (x86 with CONFIG_X86_64 and CONFIG_X86_DIRECT_GBPAGES enabled.)

       /proc/modules
              A text list of the modules that have been loaded by the system.  See also lsmod(8).

       /proc/mounts
              Before kernel 2.4.19, this file was a list of all the filesystems currently mounted on the system.
              With the introduction of per-process mount namespaces in Linux 2.4.19  (see  mount_namespaces(7)),
              this  file  became  a link to /proc/self/mounts, which lists the mount points of the process's own
              mount namespace.  The format of this file is documented in fstab(5).

       /proc/mtrr
              Memory Type Range Registers.  See the Linux  kernel  source  file  Documentation/x86/mtrr.txt  (or
              Documentation/mtrr.txt before Linux 2.6.28) for details.

       /proc/net
              This  directory  contains  various  files  and  subdirectories  containing  information  about the
              networking layer.  The files contain ASCII structures and are, therefore,  readable  with  cat(1).
              However, the standard netstat(8) suite provides much cleaner access to these files.

              With  the  advent  of  network  namespaces,  various  information relating to the network stack is
              virtualized (see namespaces(7)).  Thus, since Linux 2.6.25, /proc/net is a symbolic  link  to  the
              directory /proc/self/net, which contains the same files and directories as listed below.  However,
              these files and directories now expose information for the network namespace of which the  process
              is a member.

       /proc/net/arp
              This  holds  an ASCII readable dump of the kernel ARP table used for address resolutions.  It will
              show both dynamically learned and preprogrammed ARP entries.  The format is:

       IP address     HW type   Flags     HW address          Mask   Device
       192.168.0.50   0x1       0x2       00:50:BF:25:68:F3   *      eth0
       192.168.0.250  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here "IP address" is the IPv4 address of the machine and the "HW type" is the hardware type of the
              address  from  RFC 826.   The  flags  are  the  internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h) and the "HW address" is the data  link  layer  mapping  for  that  IP
              address if it is known.

       /proc/net/dev
              The dev pseudo-file contains network device status information.  This gives the number of received
              and sent packets, the number of errors and collisions and other basic statistics.  These are  used
              by the ifconfig(8) program to report device status.  The format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0

       /proc/net/dev_mcast
              Defined in /usr/src/linux/net/core/dev_mcast.c:

                  indx interface_name  dmi_u dmi_g dmi_address
                  2    eth0            1     0     01005e000001
                  3    eth1            1     0     01005e000001
                  4    eth2            1     0     01005e000001

       /proc/net/igmp
              Internet Group Management Protocol.  Defined in /usr/src/linux/net/core/igmp.c.

       /proc/net/rarp
              This  file  uses the same format as the arp file and contains the current reverse mapping database
              used to provide rarp(8) reverse address lookup services.  If  RARP  is  not  configured  into  the
              kernel, this file will not be present.

       /proc/net/raw
              Holds a dump of the RAW socket table.  Much of the information is not of use apart from debugging.
              The "sl" value is the kernel hash slot for the socket, the "local_address" is  the  local  address
              and  protocol  number  pair.   "St"  is  the  internal  status  of the socket.  The "tx_queue" and
              "rx_queue" are the outgoing and incoming data queue in terms of kernel memory  usage.   The  "tr",
              "tm->when",  and "rexmits" fields are not used by RAW.  The "uid" field holds the effective UID of
              the creator of the socket.

       /proc/net/snmp
              This file holds the ASCII data needed for the IP, ICMP, TCP, and UDP management information  bases
              for an SNMP agent.

       /proc/net/tcp
              Holds a dump of the TCP socket table.  Much of the information is not of use apart from debugging.
              The "sl" value is the kernel hash slot for the socket, the "local_address" is  the  local  address
              and  port  number  pair.   The  "rem_address"  is  the  remote  address  and  port number pair (if
              connected).  "St" is the internal status of the socket.  The "tx_queue"  and  "rx_queue"  are  the
              outgoing  and  incoming  data  queue  in  terms of kernel memory usage.  The "tr", "tm->when", and
              "rexmits" fields hold internal information of the kernel socket state  and  are  useful  only  for
              debugging.  The "uid" field holds the effective UID of the creator of the socket.

       /proc/net/udp
              Holds a dump of the UDP socket table.  Much of the information is not of use apart from debugging.
              The "sl" value is the kernel hash slot for the socket, the "local_address" is  the  local  address
              and  port  number  pair.   The  "rem_address"  is  the  remote  address  and  port number pair (if
              connected).  "St" is the internal status of the socket.  The "tx_queue"  and  "rx_queue"  are  the
              outgoing  and  incoming  data  queue  in  terms of kernel memory usage.  The "tr", "tm->when", and
              "rexmits" fields are not used by UDP.  The "uid" field holds the effective UID of the  creator  of
              the socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

       /proc/net/unix
              Lists the UNIX domain sockets present within the system and their status.  The format is:

 Num RefCount Protocol Flags    Type St Path
  0: 00000002 00000000 00000000 0001 03
  1: 00000001 00000000 00010000 0001 01 /dev/printer

              The fields are as follows:

              Num:      the kernel table slot number.

              RefCount: the number of users of the socket.

              Protocol: currently always 0.

              Flags:    the internal kernel flags holding the status of the socket.

              Type:     the  socket  type.  For SOCK_STREAM sockets, this is 0001; for SOCK_DGRAM sockets, it is
                        0002; and for SOCK_SEQPACKET sockets, it is 0005.

              St:       the internal state of the socket.

              Path:     the bound path (if any) of the socket.  Sockets in the abstract namespace  are  included
                        in the list, and are shown with a Path that commences with the character '@'.

       /proc/net/netfilter/nfnetlink_queue
              This file contains information about netfilter user-space queueing, if used.  Each line represents
              a queue.  Queues that have not been subscribed to by user space are not shown.

                     1   4207     0  2 65535     0     0        0  1
                    (1)   (2)    (3)(4)  (5)    (6)   (7)      (8)

              The fields in each line are:

              (1)  The ID of the queue.  This matches what is specified in the  --queue-num  or  --queue-balance
                   options to the iptables(8) NFQUEUE target.  See iptables-extensions(8) for more information.

              (2)  The netlink port ID subscribed to the queue.

              (3)  The number of packets currently queued and waiting to be processed by the application.

              (4)  The  copy  mode of the queue.  It is either 1 (metadata only) or 2 (also copy payload data to
                   user space).

              (5)  Copy range; that is, how many bytes of packet payload should be copied to user space at most.

              (6)  queue dropped.  Number of packets that had to be dropped  by  the  kernel  because  too  many
                   packets are already waiting for user space to send back the mandatory accept/drop verdicts.

              (7)  queue  user dropped.  Number of packets that were dropped within the netlink subsystem.  Such
                   drops usually happen when the corresponding socket buffer is full; that is, user space is not
                   able to read messages fast enough.

              (8)  sequence  number.  Every queued packet is associated with a (32-bit) monotonically-increasing
                   sequence number.  This shows the ID of the most recent packet queued.

              The last number exists only for compatibility reasons and is always 1.

       /proc/partitions
              Contains the major and minor numbers of each partition as well as the number of  1024-byte  blocks
              and the partition name.

       /proc/pci
              This is a listing of all PCI devices found during kernel initialization and their configuration.

              This  file  has  been  deprecated  in  favor of a new /proc interface for PCI (/proc/bus/pci).  It
              became optional in Linux 2.2 (available with CONFIG_PCI_OLD_PROC set at kernel  compilation).   It
              became  once more nonoptionally enabled in Linux 2.4.  Next, it was deprecated in Linux 2.6 (still
              available with CONFIG_PCI_LEGACY_PROC set), and finally removed altogether since Linux 2.6.17.

       /proc/profile (since Linux 2.4)
              This file is present only if the kernel was booted with the  profile=1  command-line  option.   It
              exposes kernel profiling information in a binary format for use by readprofile(1).  Writing (e.g.,
              an empty string) to this file resets the profiling counters;  on  some  architectures,  writing  a
              binary integer "profiling multiplier" of size sizeof(int) sets the profiling interrupt frequency.

       /proc/scsi
              A  directory  with  the  scsi mid-level pseudo-file and various SCSI low-level driver directories,
              which contain a file for each SCSI host in this system, all of which give the status of some  part
              of  the SCSI IO subsystem.  These files contain ASCII structures and are, therefore, readable with
              cat(1).

              You can also write to some of the files to reconfigure the subsystem or switch certain features on
              or off.

       /proc/scsi/scsi
              This is a listing of all SCSI devices known to the kernel.  The listing is similar to the one seen
              during bootup.  scsi currently supports only the add-single-device command which  allows  root  to
              add a hotplugged device to the list of known devices.

              The command

                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

              will cause host scsi1 to scan on SCSI channel 0 for a device on ID 5 LUN 0.  If there is already a
              device known on this address or the address is invalid, an error will be returned.

       /proc/scsi/[drivername]
              [drivername] can currently be NCR53c7xx, aha152x, aha1542, aha1740, aic7xxx,  buslogic,  eata_dma,
              eata_pio,  fdomain,  in2000,  pas16,  qlogic,  scsi_debug,  seagate, t128, u15-24f, ultrastore, or
              wd7000.  These directories show up for all drivers that registered at least one SCSI  HBA.   Every
              directory  contains  one  file per registered host.  Every host-file is named after the number the
              host was assigned during initialization.

              Reading these files will usually show driver and host configuration, statistics, and so on.

              Writing to these files allows different things on different hosts.  For example, with the  latency
              and  nolatency  commands,  root  can  switch  on  and  off command latency measurement code in the
              eata_dma driver.  With the lockup and unlock commands, root can control bus lockups  simulated  by
              the scsi_debug driver.

       /proc/self
              This directory refers to the process accessing the /proc filesystem, and is identical to the /proc
              directory named by the process ID of the same process.

       /proc/slabinfo
              Information about kernel caches.  See slabinfo(5) for details.

       /proc/stat
              kernel/system statistics.  Varies with architecture.  Common entries include:

              cpu 10132153 290696 3084719 46828483 16683 0 25195 0 175628 0
              cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
                     The amount  of  time,  measured  in  units  of  USER_HZ  (1/100ths  of  a  second  on  most
                     architectures,  use sysconf(_SC_CLK_TCK) to obtain the right value), that the system ("cpu"
                     line) or the specific CPU ("cpuN" line) spent in various states:

                     user   (1) Time spent in user mode.

                     nice   (2) Time spent in user mode with low priority (nice).

                     system (3) Time spent in system mode.

                     idle   (4) Time spent in the idle task.  This value should  be  USER_HZ  times  the  second
                            entry in the /proc/uptime pseudo-file.

                     iowait (since Linux 2.5.41)
                            (5) Time waiting for I/O to complete.  This value is not reliable, for the following
                            reasons:

                            1. The CPU will not wait for I/O to complete; iowait is the  time  that  a  task  is
                               waiting  for  I/O  to  complete.  When a CPU goes into idle state for outstanding
                               task I/O, another task will be scheduled on this CPU.

                            2. On a multi-core CPU, the task waiting for I/O to complete is not running  on  any
                               CPU, so the iowait of each CPU is difficult to calculate.

                            3. The value in this field may decrease in certain conditions.

                     irq (since Linux 2.6.0-test4)
                            (6) Time servicing interrupts.

                     softirq (since Linux 2.6.0-test4)
                            (7) Time servicing softirqs.

                     steal (since Linux 2.6.11)
                            (8)  Stolen time, which is the time spent in other operating systems when running in
                            a virtualized environment

                     guest (since Linux 2.6.24)
                            (9) Time spent running a virtual CPU for guest operating systems under  the  control
                            of the Linux kernel.

                     guest_nice (since Linux 2.6.33)
                            (10) Time spent running a niced guest (virtual CPU for guest operating systems under
                            the control of the Linux kernel).

              page 5741 1808
                     The number of pages the system paged in and the number that were paged out (from disk).

              swap 1 0
                     The number of swap pages that have been brought in and out.

              intr 1462898
                     This line shows counts of interrupts serviced since boot time, for  each  of  the  possible
                     system  interrupts.   The  first  column  is the total of all interrupts serviced including
                     unnumbered architecture specific interrupts; each subsequent column is the total  for  that
                     particular  numbered  interrupt.  Unnumbered interrupts are not shown, only summed into the
                     total.

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
                     (Linux 2.4 only)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).

              processes 86031
                     Number of forks since boot.

              procs_running 6
                     Number of processes in runnable state.  (Linux 2.5.45 onward.)

              procs_blocked 2
                     Number of processes blocked waiting for I/O to complete.  (Linux 2.5.45 onward.)

              softirq 229245889 94 60001584 13619 5175704 2471304 28 51212741 59130143 0 51240672
                     This line shows the number of softirq for all CPUs.  The first column is the total  of  all
                     softirqs  and  each  subsequent  column is the total for particular softirq.  (Linux 2.6.31
                     onward.)

       /proc/swaps
              Swap areas in use.  See also swapon(8).

       /proc/sys
              This directory (present since 1.3.57) contains a number of files and subdirectories  corresponding
              to  kernel  variables.   These  variables  can  be  read  and  sometimes  modified using the /proc
              filesystem, and the (deprecated) sysctl(2) system call.

              String values may be terminated by either '\0' or '\n'.

              Integer and long values may be written either in decimal or in hexadecimal notation (e.g. 0x3FFF).
              When  writing  multiple  integer  or  long  values, these may be separated by any of the following
              whitespace characters: ' ', '\t', or '\n'.  Using other separators leads to the error EINVAL.

       /proc/sys/abi (since Linux 2.4.10)
              This directory may contain files with application binary information.  See the Linux kernel source
              file Documentation/sysctl/abi.txt for more information.

       /proc/sys/debug
              This directory may be empty.

       /proc/sys/dev
              This  directory  contains device-specific information (e.g., dev/cdrom/info).  On some systems, it
              may be empty.

       /proc/sys/fs
              This directory contains the files and subdirectories for kernel variables related to filesystems.

       /proc/sys/fs/binfmt_misc
              Documentation for files in this directory can be found in the Linux  kernel  source  in  the  file
              Documentation/admin-guide/binfmt-misc.rst (or in Documentation/binfmt_misc.txt on older kernels).

       /proc/sys/fs/dentry-state (since Linux 2.2)
              This  file  contains  information  about  the  status  of  the directory cache (dcache).  The file
              contains six  numbers,  nr_dentry,  nr_unused,  age_limit  (age  in  seconds),  want_pages  (pages
              requested by system) and two dummy values.

              * nr_dentry  is  the number of allocated dentries (dcache entries).  This field is unused in Linux
                2.2.

              * nr_unused is the number of unused dentries.

              * age_limit is the age in seconds after which dcache entries  can  be  reclaimed  when  memory  is
                short.

              * want_pages  is  nonzero  when  the  kernel has called shrink_dcache_pages() and the dcache isn't
                pruned yet.

       /proc/sys/fs/dir-notify-enable
              This file can be used to disable or enable the  dnotify  interface  described  in  fcntl(2)  on  a
              system-wide basis.  A value of 0 in this file disables the interface, and a value of 1 enables it.

       /proc/sys/fs/dquot-max
              This file shows the maximum number of cached disk quota entries.  On some (2.4) systems, it is not
              present.  If the number of free cached disk quota entries is very low and you  have  some  awesome
              number of simultaneous system users, you might want to raise the limit.

       /proc/sys/fs/dquot-nr
              This  file  shows  the  number  of  allocated disk quota entries and the number of free disk quota
              entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
              This directory contains the file max_user_watches, which can be used to limit the amount of kernel
              memory consumed by the epoll interface.  For further details, see epoll(7).

       /proc/sys/fs/file-max
              This file defines a system-wide limit on the number of open files for all processes.  System calls
              that fail when encountering this limit fail with the error ENFILE.  (See also setrlimit(2),  which
              can  be  used  by a process to set the per-process limit, RLIMIT_NOFILE, on the number of files it
              may open.)  If you get lots of error messages in the kernel log about running out of file  handles
              (look for "VFS: file-max limit <number> reached"), try increasing this value:

                  echo 100000 > /proc/sys/fs/file-max

              Privileged processes (CAP_SYS_ADMIN) can override the file-max limit.

       /proc/sys/fs/file-nr
              This  (read-only)  file  contains  three  numbers: the number of allocated file handles (i.e., the
              number of files presently opened); the number of free file handles; and the maximum number of file
              handles  (i.e., the same value as /proc/sys/fs/file-max).  If the number of allocated file handles
              is close to the maximum, you should consider increasing the maximum.  Before Linux 2.6, the kernel
              allocated  file handles dynamically, but it didn't free them again.  Instead the free file handles
              were kept in a list for reallocation; the "free file handles" value indicates  the  size  of  that
              list.   A  large  number of free file handles indicates that there was a past peak in the usage of
              open file handles.  Since Linux 2.6, the kernel does deallocate freed file handles, and the  "free
              file handles" value is always zero.

       /proc/sys/fs/inode-max (only present until Linux 2.2)
              This  file contains the maximum number of in-memory inodes.  This value should be 3–4 times larger
              than the value in file-max, since stdin, stdout and network sockets also need an inode  to  handle
              them.  When you regularly run out of inodes, you need to increase this value.

              Starting  with Linux 2.4, there is no longer a static limit on the number of inodes, and this file
              is removed.

       /proc/sys/fs/inode-nr
              This file contains the first two values from inode-state.

       /proc/sys/fs/inode-state
              This file contains seven numbers: nr_inodes, nr_free_inodes,  preshrink,  and  four  dummy  values
              (always zero).

              nr_inodes  is the number of inodes the system has allocated.  nr_free_inodes represents the number
              of free inodes.

              preshrink is nonzero when the nr_inodes > inode-max and the system needs to prune the  inode  list
              instead of allocating more; since Linux 2.4, this field is a dummy value (always zero).

       /proc/sys/fs/inotify (since Linux 2.6.13)
              This  directory  contains  files max_queued_events, max_user_instances, and max_user_watches, that
              can be used to limit the amount of kernel memory consumed by the inotify interface.   For  further
              details, see inotify(7).

       /proc/sys/fs/lease-break-time
              This  file  specifies  the  grace  period that the kernel grants to a process holding a file lease
              (fcntl(2)) after it has sent a signal to that process notifying it that another process is waiting
              to  open  the  file.  If the lease holder does not remove or downgrade the lease within this grace
              period, the kernel forcibly breaks the lease.

       /proc/sys/fs/leases-enable
              This file can be used to enable or disable file leases (fcntl(2)) on a system-wide basis.  If this
              file contains the value 0, leases are disabled.  A nonzero value enables leases.

       /proc/sys/fs/mount-max (since Linux 4.9)
              The value in this file specifies the maximum number of mounts that may exist in a mount namespace.
              The default value in this file is 100,000.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
              This directory contains files msg_max, msgsize_max, and queues_max, controlling the resources used
              by POSIX message queues.  See mq_overview(7) for details.

       /proc/sys/fs/nr_open (since Linux 2.6.25)
              This  file  imposes  ceiling  on the value to which the RLIMIT_NOFILE resource limit can be raised
              (see getrlimit(2)).  This ceiling is enforced for both unprivileged and privileged  process.   The
              default  value  in  this file is 1048576.  (Before Linux 2.6.25, the ceiling for RLIMIT_NOFILE was
              hard-coded to the same value.)

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
              These files allow you to change the value of the fixed UID and GID.  The default is  65534.   Some
              filesystems  support only 16-bit UIDs and GIDs, although in Linux UIDs and GIDs are 32 bits.  When
              one of these filesystems is mounted with writes enabled, any UID or GID that would exceed 65535 is
              translated to the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
              See pipe(7).

       /proc/sys/fs/pipe-user-pages-hard (since Linux 4.5)
              See pipe(7).

       /proc/sys/fs/pipe-user-pages-soft (since Linux 4.5)
              See pipe(7).

       /proc/sys/fs/protected_hardlinks (since Linux 3.6)
              When  the value in this file is 0, no restrictions are placed on the creation of hard links (i.e.,
              this is the historical behavior before Linux 3.6).  When the value in this file is 1, a hard  link
              can be created to a target file only if one of the following conditions is true:

              *  The  calling process has the CAP_FOWNER capability in its user namespace and the file UID has a
                 mapping in the namespace.

              *  The filesystem UID of the process creating the link matches the owner (UID) of the target  file
                 (as  described  in  credentials(7),  a  process's  filesystem  UID  is normally the same as its
                 effective UID).

              *  All of the following conditions are true:

                  •  the target is a regular file;

                  •  the target file does not have its set-user-ID mode bit enabled;

                  •  the target file does not have both its set-group-ID and group-executable mode bits enabled;
                     and

                  •  the  caller  has  permission  to  read  and  write  the  target file (either via the file's
                     permissions mask or because it has suitable capabilities).

              The default value in this file is 0.  Setting the value to 1  prevents  a  longstanding  class  of
              security  issues caused by hard-link-based time-of-check, time-of-use races, most commonly seen in
              world-writable directories such as /tmp.  The common method of exploiting this flaw  is  to  cross
              privilege  boundaries  when  following a given hard link (i.e., a root process follows a hard link
              created by another user).  Additionally, on  systems  without  separated  partitions,  this  stops
              unauthorized  users  from  "pinning"  vulnerable  set-user-ID and set-group-ID files against being
              upgraded by the administrator, or linking to special files.

       /proc/sys/fs/protected_symlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed on following  symbolic  links  (i.e.,
              this  is  the  historical  behavior before Linux 3.6).  When the value in this file is 1, symbolic
              links are followed only in the following circumstances:

              *  the filesystem UID of the process following the link matches the owner (UID)  of  the  symbolic
                 link  (as  described  in credentials(7), a process's filesystem UID is normally the same as its
                 effective UID);

              *  the link is not in a sticky world-writable directory; or

              *  the symbolic link and its parent directory have the same owner (UID)

              A system call that fails to follow a symbolic link because of the above restrictions  returns  the
              error EACCES in errno.

              The  default  value  in  this  file  is  0.  Setting the value to 1 avoids a longstanding class of
              security issues based on time-of-check, time-of-use races when accessing symbolic links.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
              The value in this file is assigned to a process's "dumpable" flag in the  circumstances  described
              in  prctl(2).   In  effect, the value in this file determines whether core dump files are produced
              for set-user-ID or otherwise protected/tainted binaries.  The "dumpable" setting also affects  the
              ownership of files in a process's /proc/[pid] directory, as described above.

              Three different integer values can be specified:

              0 (default)
                     This  provides  the  traditional  (pre-Linux  2.6.13)  behavior.   A  core dump will not be
                     produced for a process which has changed credentials (by calling seteuid(2), setgid(2),  or
                     similar,  or  by  executing a set-user-ID or set-group-ID program) or whose binary does not
                     have read permission enabled.

              1 ("debug")
                     All processes dump core when possible.  (Reasons why a process might nevertheless not  dump
                     core  are  described  in core(5).)  The core dump is owned by the filesystem user ID of the
                     dumping process and no  security  is  applied.   This  is  intended  for  system  debugging
                     situations  only: this mode is insecure because it allows unprivileged users to examine the
                     memory contents of privileged processes.

              2 ("suidsafe")
                     Any binary which normally would not be dumped (see "0" above) is dumped  readable  by  root
                     only.   This allows the user to remove the core dump file but not to read it.  For security
                     reasons core dumps in this mode will not overwrite one another or other files.   This  mode
                     is   appropriate  when  administrators  are  attempting  to  debug  problems  in  a  normal
                     environment.

                     Additionally, since Linux 3.6, /proc/sys/kernel/core_pattern must  either  be  an  absolute
                     pathname or a pipe command, as detailed in core(5).  Warnings will be written to the kernel
                     log if core_pattern does not follow these rules, and no core dump will be produced.

              For details of the effect of a process's "dumpable" setting on ptrace access  mode  checking,  see
              ptrace(2).

       /proc/sys/fs/super-max
              This  file  controls  the  maximum  number  of superblocks, and thus the maximum number of mounted
              filesystems the kernel can have.  You need increase only super-max  if  you  need  to  mount  more
              filesystems than the current value in super-max allows you to.

       /proc/sys/fs/super-nr
              This file contains the number of filesystems currently mounted.

       /proc/sys/kernel
              This directory contains files controlling a range of kernel parameters, as described below.

       /proc/sys/kernel/acct
              This  file  contains  three  numbers:  highwater,  lowwater,  and frequency.  If BSD-style process
              accounting is enabled, these values control its behavior.  If free space on filesystem  where  the
              log  lives  goes  below lowwater percent, accounting suspends.  If free space gets above highwater
              percent, accounting resumes.  frequency determines how often the kernel checks the amount of  free
              space  (value  is in seconds).  Default values are 4, 2 and 30.  That is, suspend accounting if 2%
              or less space is free; resume it if 4% or more space is free; consider information about amount of
              free space valid for 30 seconds.

       /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
              From  Linux  2.6.27  to  3.18,  this  file  was  used  to  control  recomputing  of  the  value in
              /proc/sys/kernel/msgmni  upon  the  addition  or  removal  of  memory  or   upon   IPC   namespace
              creation/removal.   Echoing "1" into this file enabled msgmni automatic recomputing (and triggered
              a recomputation of msgmni based on the current amount  of  available  memory  and  number  of  IPC
              namespaces).   Echoing  "0"  disabled  automatic  recomputing.   (Automatic  recomputing  was also
              disabled if a value was explicitly assigned to /proc/sys/kernel/msgmni.)   The  default  value  in
              auto_msgmni was 1.

              Since  Linux  3.19,  the  content  of this file has no effect (because msgmni defaults to near the
              maximum value possible), and reads from this file always return the value "0".

       /proc/sys/kernel/cap_last_cap (since Linux 3.2)
              See capabilities(7).

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
              This file holds the value of the kernel capability bounding set (expressed  as  a  signed  decimal
              number).   This  set  is  ANDed  against the capabilities permitted to a process during execve(2).
              Starting with Linux 2.6.25, the system-wide capability bounding set disappeared, and was  replaced
              by a per-thread bounding set; see capabilities(7).

       /proc/sys/kernel/core_pattern
              See core(5).

       /proc/sys/kernel/core_pipe_limit
              See core(5).

       /proc/sys/kernel/core_uses_pid
              See core(5).

       /proc/sys/kernel/ctrl-alt-del
              This file controls the handling of Ctrl-Alt-Del from the keyboard.  When the value in this file is
              0, Ctrl-Alt-Del is trapped and sent to the init(1) program to handle a graceful restart.  When the
              value  is  greater  than  zero, Linux's reaction to a Vulcan Nerve Pinch (tm) will be an immediate
              reboot, without even syncing its dirty buffers.  Note:  when  a  program  (like  dosemu)  has  the
              keyboard  in "raw" mode, the ctrl-alt-del is intercepted by the program before it ever reaches the
              kernel tty layer, and it's up to the program to decide what to do with it.

       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
              The value in this file determines who can see kernel syslog contents.  A value of 0 in  this  file
              imposes  no  restrictions.   If  the value is 1, only privileged users can read the kernel syslog.
              (See syslog(2) for more details.)  Since Linux 3.4, only users with the  CAP_SYS_ADMIN  capability
              may change the value in this file.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
              can  be  used to set the NIS/YP domainname and the hostname of your box in exactly the same way as
              the commands domainname(1) and hostname(1), that is:

                  # echo 'darkstar' > /proc/sys/kernel/hostname
                  # echo 'mydomain' > /proc/sys/kernel/domainname

              has the same effect as

                  # hostname 'darkstar'
                  # domainname 'mydomain'

              Note, however, that the classic darkstar.frop.org has the hostname "darkstar"  and  DNS  (Internet
              Domain  Name  Server)  domainname "frop.org", not to be confused with the NIS (Network Information
              Service) or YP (Yellow Pages) domainname.  These two domain names are in general different.  For a
              detailed discussion see the hostname(1) man page.

       /proc/sys/kernel/hotplug
              This  file  contains  the  path  for  the hotplug policy agent.  The default value in this file is
              /sbin/hotplug.

       /proc/sys/kernel/htab-reclaim (before Linux 2.4.9.2)
              (PowerPC only) If this file is set  to  a  nonzero  value,  the  PowerPC  htab  (see  kernel  file
              Documentation/powerpc/ppc_htab.txt) is pruned each time the system hits the idle loop.

       /proc/sys/kernel/keys/*
              This  directory  contains  various  files that define parameters and limits for the key-management
              facility.  These files are described in keyrings(7).

       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
              The value in this file determines whether kernel addresses are exposed via /proc files  and  other
              interfaces.   A  value  of  0  in  this  file  imposes no restrictions.  If the value is 1, kernel
              pointers printed using the %pK format specifier will be replaced with zeros unless  the  user  has
              the  CAP_SYSLOG  capability.   If  the  value  is  2, kernel pointers printed using the %pK format
              specifier will be replaced with zeros regardless of the user's capabilities.  The initial  default
              value  for  this  file  was 1, but the default was changed to 0 in Linux 2.6.39.  Since Linux 3.4,
              only users with the CAP_SYS_ADMIN capability can change the value in this file.

       /proc/sys/kernel/l2cr
              (PowerPC only) This file contains a flag that controls the L2 cache of G3 processor boards.  If 0,
              the cache is disabled.  Enabled if nonzero.

       /proc/sys/kernel/modprobe
              This  file  contains  the path for the kernel module loader.  The default value is /sbin/modprobe.
              The file is present only if the kernel is built with  the  CONFIG_MODULES  (CONFIG_KMOD  in  Linux
              2.6.26   and  earlier)  option  enabled.   It  is  described  by  the  Linux  kernel  source  file
              Documentation/kmod.txt (present only in kernel 2.4 and earlier).

       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
              A toggle value indicating if modules are allowed to be loaded  in  an  otherwise  modular  kernel.
              This  toggle  defaults  to  off  (0),  but can be set true (1).  Once true, modules can be neither
              loaded nor unloaded, and the toggle cannot be set back to false.  The file is present only if  the
              kernel is built with the CONFIG_MODULES option enabled.

       /proc/sys/kernel/msgmax (since Linux 2.2)
              This  file  defines a system-wide limit specifying the maximum number of bytes in a single message
              written on a System V message queue.

       /proc/sys/kernel/msgmni (since Linux 2.4)
              This file defines the system-wide limit on the number of  message  queue  identifiers.   See  also
              /proc/sys/kernel/auto_msgmni.

       /proc/sys/kernel/msgmnb (since Linux 2.2)
              This  file  defines  a  system-wide  parameter  used  to  initialize  the  msg_qbytes  setting for
              subsequently created message queues.  The msg_qbytes setting specifies the maximum number of bytes
              that may be written to the message queue.

       /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
              This  is  a  read-only  file  that  displays  the  upper  limit on the number of a process's group
              memberships.

       /proc/sys/kernel/ns_last_pid (since Linux 3.3)
              See pid_namespaces(7).

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
              These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
              These files duplicate the files /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid.

       /proc/sys/kernel/panic
              This file gives read/write access to the kernel variable panic_timeout.   If  this  is  zero,  the
              kernel will loop on a panic; if nonzero, it indicates that the kernel should autoreboot after this
              number of seconds.  When you use the software watchdog device driver, the recommended  setting  is
              60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
              This  file  controls  the  kernel's  behavior  when  an  oops or BUG is encountered.  If this file
              contains 0, then the system tries to continue operation.  If it contains 1, then the system delays
              a  few  seconds  (to  give  klogd  time  to  record  the  oops  output)  and  then panics.  If the
              /proc/sys/kernel/panic file is also nonzero, then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
              This file specifies the value at which PIDs wrap around (i.e., the  value  in  this  file  is  one
              greater than the maximum PID).  PIDs greater than this value are not allocated; thus, the value in
              this file also acts as a system-wide limit on the total number  of  processes  and  threads.   The
              default  value  for this file, 32768, results in the same range of PIDs as on earlier kernels.  On
              32-bit platforms, 32768 is the maximum value for pid_max.  On 64-bit systems, pid_max can  be  set
              to any value up to 2^22 (PID_MAX_LIMIT, approximately 4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
              This  file  contains  a flag.  If set, Linux-PPC will use the "nap" mode of powersaving, otherwise
              the "doze" mode will be used.

       /proc/sys/kernel/printk
              See syslog(2).

       /proc/sys/kernel/pty (since Linux 2.6.4)
              This directory contains two files relating to the number of UNIX 98 pseudoterminals  (see  pts(4))
              on the system.

       /proc/sys/kernel/pty/max
              This file defines the maximum number of pseudoterminals.

       /proc/sys/kernel/pty/nr
              This read-only file indicates how many pseudoterminals are currently in use.

       /proc/sys/kernel/random
              This directory contains various parameters controlling the operation of the file /dev/random.  See
              random(4) for further information.

       /proc/sys/kernel/random/uuid (since Linux 2.4)
              Each read from this read-only file returns a randomly generated 128-bit UUID, as a string  in  the
              standard UUID format.

       /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
              Select  the address space layout randomization (ASLR) policy for the system (on architectures that
              support ASLR).  Three values are supported for this file:

              0  Turn ASLR off.  This is the default for architectures that don't support  ASLR,  and  when  the
                 kernel is booted with the norandmaps parameter.

              1  Make  the  addresses  of  mmap(2)  allocations, the stack, and the VDSO page randomized.  Among
                 other things, this means that shared libraries will be loaded  at  randomized  addresses.   The
                 text segment of PIE-linked binaries will also be loaded at a randomized address.  This value is
                 the default if the kernel was configured with CONFIG_COMPAT_BRK.

              2  (Since Linux 2.6.25) Also support heap randomization.  This value is the default if the  kernel
                 was not configured with CONFIG_COMPAT_BRK.

       /proc/sys/kernel/real-root-dev
              This  file  is documented in the Linux kernel source file Documentation/admin-guide/initrd.rst (or
              Documentation/initrd.txt before Linux 4.10).

       /proc/sys/kernel/reboot-cmd (Sparc only)
              This file seems to be a way to give an argument to the SPARC ROM/Flash boot loader.  Maybe to tell
              it what to do after rebooting?

       /proc/sys/kernel/rtsig-max
              (Only  in  kernels  up to and including 2.6.7; see setrlimit(2)) This file can be used to tune the
              maximum number of POSIX real-time (queued) signals that can be outstanding in the system.

       /proc/sys/kernel/rtsig-nr
              (Only in kernels up to and including 2.6.7.)  This  file  shows  the  number  of  POSIX  real-time
              signals currently queued.

       /proc/[pid]/sched_autogroup_enabled (since Linux 2.6.38)
              See sched(7).

       /proc/sys/kernel/sched_child_runs_first (since Linux 2.6.23)
              If  this file contains the value zero, then, after a fork(2), the parent is first scheduled on the
              CPU.  If the file contains a nonzero value, then the child is scheduled first  on  the  CPU.   (Of
              course,  on  a multiprocessor system, the parent and the child might both immediately be scheduled
              on a CPU.)

       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
              See sched_rr_get_interval(2).

       /proc/sys/kernel/sched_rt_period_us (since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/sched_rt_runtime_us (since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/seccomp (since Linux 4.14)
              This directory provides additional seccomp information  and  configuration.   See  seccomp(2)  for
              further details.

       /proc/sys/kernel/sem (since Linux 2.4)
              This  file  contains  4 numbers defining limits for System V IPC semaphores.  These fields are, in
              order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A system-wide limit on the number of semaphores in all semaphore sets.

              SEMOPM  The maximum number of operations that may be specified in a semop(2) call.

              SEMMNI  A system-wide limit on the maximum number of semaphore identifiers.

       /proc/sys/kernel/sg-big-buff
              This file shows the size of the generic SCSI device (sg) buffer.  You can't tune it just yet,  but
              you  could  change  it  at  compile  time  by  editing include/scsi/sg.h and changing the value of
              SG_BIG_BUFF.  However, there shouldn't be any reason to change this value.

       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
              If this file is set to 1, all System V shared memory segments will be marked  for  destruction  as
              soon  as  the number of attached processes falls to zero; in other words, it is no longer possible
              to create shared memory segments that exist independently of any attached process.

              The effect is as though a shmctl(2) IPC_RMID is performed on all existing segments as well as  all
              segments  created in the future (until this file is reset to 0).  Note that existing segments that
              are attached to no process will be immediately destroyed when this file is set to 1.  Setting this
              option  will  also destroy segments that were created, but never attached, upon termination of the
              process that created the segment with shmget(2).

              Setting this file to 1 provides a way of ensuring that all System V  shared  memory  segments  are
              counted  against  the  resource  usage  and  resource  limits (see the description of RLIMIT_AS in
              getrlimit(2)) of at least one process.

              Because setting this file to 1 produces behavior that is nonstandard and could also break existing
              applications,  the  default  value  in this file is 0.  Set this file to 1 only if you have a good
              understanding of the semantics of the applications using System V shared memory on your system.

       /proc/sys/kernel/shmall (since Linux 2.2)
              This file contains the system-wide limit on the total number of pages of System V shared memory.

       /proc/sys/kernel/shmmax (since Linux 2.2)
              This file can be used to query and set the run-time limit on the maximum  (System  V  IPC)  shared
              memory  segment  size  that can be created.  Shared memory segments up to 1GB are now supported in
              the kernel.  This value defaults to SHMMAX.

       /proc/sys/kernel/shmmni (since Linux 2.4)
              This file specifies the system-wide maximum number of System V shared memory segments that can  be
              created.

       /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
              The  value in this file determines how the file offset affects the behavior of updating entries in
              files under /proc/sys.  The file has three possible values:

              -1  This provides legacy handling, with no printk warnings.  Each write(2) must fully contain  the
                  value to be written, and multiple writes on the same file descriptor will overwrite the entire
                  value, regardless of the file position.

              0   (default) This provides the same behavior as for -1,  but  printk  warnings  are  written  for
                  processes that perform writes when the file offset is not 0.

              1   Respect  the  file  offset  when  writing  strings into /proc/sys files.  Multiple writes will
                  append to the value buffer.  Anything written beyond the maximum length of  the  value  buffer
                  will  be ignored.  Writes to numeric /proc/sys entries must always be at file offset 0 and the
                  value must be fully contained in the buffer provided to write(2).

       /proc/sys/kernel/sysrq
              This file controls the functions allowed to be invoked by the SysRq key.   By  default,  the  file
              contains  1  meaning that every possible SysRq request is allowed (in older kernel versions, SysRq
              was disabled by default, and you were required to specifically enable it at run-time, but this  is
              not the case any more).  Possible values in this file are:

              0    Disable sysrq completely

              1    Enable all functions of sysrq

              > 1  Bit mask of allowed sysrq functions, as follows:
                     2  Enable control of console logging level
                     4  Enable control of keyboard (SAK, unraw)
                     8  Enable debugging dumps of processes etc.
                    16  Enable sync command
                    32  Enable remount read-only
                    64  Enable signaling of processes (term, kill, oom-kill)
                   128  Allow reboot/poweroff
                   256  Allow nicing of all real-time tasks

              This  file  is present only if the CONFIG_MAGIC_SYSRQ kernel configuration option is enabled.  For
              further  details  see  the  Linux  kernel  source  file  Documentation/admin-guide/sysrq.rst   (or
              Documentation/sysrq.txt before Linux 4.10).

       /proc/sys/kernel/version
              This file contains a string such as:

                  #5 Wed Feb 25 21:49:24 MET 1998

              The "#5" means that this is the fifth kernel built from this source base and the date following it
              indicates the time the kernel was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
              This file specifies the system-wide limit on the number of threads (tasks) that can be created  on
              the system.

              Since  Linux 4.1, the value that can be written to threads-max is bounded.  The minimum value that
              can be written is  20.   The  maximum  value  that  can  be  written  is  given  by  the  constant
              FUTEX_TID_MASK  (0x3fffffff).   If  a  value  outside of this range is written to threads-max, the
              error EINVAL occurs.

              The value written is checked against the available RAM pages.   If  the  thread  structures  would
              occupy too much (more than 1/8th) of the available RAM pages, threads-max is reduced accordingly.

       /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
              See ptrace(2).

       /proc/sys/kernel/zero-paged (PowerPC only)
              This  file  contains  a  flag.   When enabled (nonzero), Linux-PPC will pre-zero pages in the idle
              loop, possibly speeding up get_free_pages.

       /proc/sys/net
              This directory contains networking stuff.  Explanations for some of the files under this directory
              can be found in tcp(7) and ip(7).

       /proc/sys/net/core/bpf_jit_enable
              See bpf(2).

       /proc/sys/net/core/somaxconn
              This  file defines a ceiling value for the backlog argument of listen(2); see the listen(2) manual
              page for details.

       /proc/sys/proc
              This directory may be empty.

       /proc/sys/sunrpc
              This directory supports Sun remote procedure call for network filesystem (NFS).  On some  systems,
              it is not present.

       /proc/sys/user (since Linux 4.9)
              See namespaces(7).

       /proc/sys/vm
              This directory contains files for memory management tuning, buffer and cache management.

       /proc/sys/vm/admin_reserve_kbytes (since Linux 3.10)
              This  file  defines  the  amount of free memory (in KiB) on the system that should be reserved for
              users with the capability CAP_SYS_ADMIN.

              The default value in this file is the minimum of [3% of free pages, 8MiB] expressed as  KiB.   The
              default  is  intended  to  provide  enough  for  the  superuser  to  log in and kill a process, if
              necessary, under the default overcommit 'guess' mode (i.e., 0 in /proc/sys/vm/overcommit_memory).

              Systems running in "overcommit never" mode  (i.e.,  2  in  /proc/sys/vm/overcommit_memory)  should
              increase  the  value in this file to account for the full virtual memory size of the programs used
              to recover (e.g., login(1) ssh(1), and top(1)) Otherwise, the superuser may not be able to log  in
              to recover the system.  For example, on x86-64 a suitable value is 131072 (128MiB reserved).

              Changing the value in this file takes effect whenever an application requests memory.

       /proc/sys/vm/compact_memory (since Linux 2.6.35)
              When  1  is  written  to  this file, all zones are compacted such that free memory is available in
              contiguous  blocks  where  possible.   The  effect  of  this  action  can  be  seen  by  examining
              /proc/buddyinfo.

              Present only if the kernel was configured with CONFIG_COMPACTION.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
              Writing  to  this  file  causes the kernel to drop clean caches, dentries, and inodes from memory,
              causing that memory to become free.   This  can  be  useful  for  memory  management  testing  and
              performing  reproducible  filesystem benchmarks.  Because writing to this file causes the benefits
              of caching to be lost, it can degrade overall system performance.

              To free pagecache, use:

                  echo 1 > /proc/sys/vm/drop_caches

              To free dentries and inodes, use:

                  echo 2 > /proc/sys/vm/drop_caches

              To free pagecache, dentries and inodes, use:

                  echo 3 > /proc/sys/vm/drop_caches

              Because writing to this file is a nondestructive operation and dirty objects are not freeable, the
              user should run sync(1) first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
              If  nonzero,  this  disables  the new 32-bit memory-mapping layout; the kernel will use the legacy
              (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
              Control how to kill processes when an uncorrected memory error  (typically  a  2-bit  error  in  a
              memory module) that cannot be handled by the kernel is detected in the background by hardware.  In
              some cases (like the page still having a valid copy on disk), the kernel will handle  the  failure
              transparently without affecting any applications.  But if there is no other up-to-date copy of the
              data, it will kill processes to prevent any data corruptions from propagating.

              The file has one of the following values:

              1:  Kill all processes that have the corrupted-and-not-reloadable  page  mapped  as  soon  as  the
                  corruption  is  detected.   Note  that this is not supported for a few types of pages, such as
                  kernel internally allocated data or the swap cache, but works for the majority of user pages.

              0:  Unmap the corrupted page from all processes and kill a process only if it tries to access  the
                  page.

              The  kill  is  performed  using  a SIGBUS signal with si_code set to BUS_MCEERR_AO.  Processes can
              handle this if they want to; see sigaction(2) for more details.

              This feature is active only on architectures/platforms with advanced machine  check  handling  and
              depends on the hardware capabilities.

              Applications  can  override  the  memory_failure_early_kill setting individually with the prctl(2)
              PR_MCE_KILL operation.

              Present only if the kernel was configured with CONFIG_MEMORY_FAILURE.

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
              Enable memory failure recovery (when supported by the platform)

              1:  Attempt recovery.

              0:  Always panic on a memory failure.

              Present only if the kernel was configured with CONFIG_MEMORY_FAILURE.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
              Enables a system-wide task dump (excluding kernel threads) to be produced when the kernel performs
              an  OOM-killing.   The  dump  includes  the following information for each task (thread, process):
              thread ID, real user ID, thread group ID (process ID), virtual memory size, resident set size, the
              CPU that the task is scheduled on, oom_adj score (see the description of /proc/[pid]/oom_adj), and
              command name.  This is helpful to determine why the OOM-killer was invoked  and  to  identify  the
              rogue task that caused it.

              If  this  contains  the  value  zero,  this information is suppressed.  On very large systems with
              thousands of tasks, it may not be feasible to dump the memory  state  information  for  each  one.
              Such  systems  should  not  be  forced  to  incur a performance penalty in OOM situations when the
              information may not be desired.

              If this is set to nonzero, this information is shown whenever  the  OOM-killer  actually  kills  a
              memory-hogging task.

              The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
              This enables or disables killing the OOM-triggering task in out-of-memory situations.

              If  this  is  set  to zero, the OOM-killer will scan through the entire tasklist and select a task
              based on heuristics to kill.  This normally selects a rogue memory-hogging task that  frees  up  a
              large amount of memory when killed.

              If  this  is set to nonzero, the OOM-killer simply kills the task that triggered the out-of-memory
              condition.  This avoids a possibly expensive tasklist scan.

              If /proc/sys/vm/panic_on_oom is nonzero, it takes  precedence  over  whatever  value  is  used  in
              /proc/sys/vm/oom_kill_allocating_task.

              The default value is 0.

       /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
              This  writable  file  provides an alternative to /proc/sys/vm/overcommit_ratio for controlling the
              CommitLimit when /proc/sys/vm/overcommit_memory has the value 2.  It allows the amount  of  memory
              overcommitting  to  be  specified as an absolute value (in kB), rather than as a percentage, as is
              done with overcommit_ratio.  This allows for finer-grained control of CommitLimit on systems  with
              extremely large memory sizes.

              Only  one  of overcommit_kbytes or overcommit_ratio can have an effect: if overcommit_kbytes has a
              nonzero value, then it is used to  calculate  CommitLimit,  otherwise  overcommit_ratio  is  used.
              Writing a value to either of these files causes the value in the other file to be set to zero.

       /proc/sys/vm/overcommit_memory
              This file contains the kernel virtual memory accounting mode.  Values are:

                     0: heuristic overcommit (this is the default)
                     1: always overcommit, never check
                     2: always check, never overcommit

              In  mode  0,  calls  of  mmap(2) with MAP_NORESERVE are not checked, and the default check is very
              weak, leading to the risk of getting a process "OOM-killed".

              In mode 1, the kernel pretends there is always enough memory, until memory actually runs out.  One
              use  case  for this mode is scientific computing applications that employ large sparse arrays.  In
              Linux kernel versions before 2.6.0, any nonzero value implies mode 1.

              In mode 2 (available since Linux 2.6), the total virtual  address  space  that  can  be  allocated
              (CommitLimit in /proc/meminfo) is calculated as

                  CommitLimit = (total_RAM - total_huge_TLB) *
                                overcommit_ratio / 100 + total_swap

              where:

                   *  total_RAM is the total amount of RAM on the system;

                   *  total_huge_TLB is the amount of memory set aside for huge pages;

                   *  overcommit_ratio is the value in /proc/sys/vm/overcommit_ratio; and

                   *  total_swap is the amount of swap space.

              For  example,  on  a  system  with  16GB of physical RAM, 16GB of swap, no space dedicated to huge
              pages, and an overcommit_ratio of 50, this formula yields a CommitLimit of 24GB.

              Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes is nonzero, then  CommitLimit  is
              instead calculated as:

                  CommitLimit = overcommit_kbytes + total_swap

              See       also       the      description      of      /proc/sys/vm/admiin_reserve_kbytes      and
              /proc/sys/vm/user_reserve_kbytes.

       /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
              This writable file defines a percentage by which memory can be overcommitted.  The  default  value
              in the file is 50.  See the description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
              This enables or disables a kernel panic in an out-of-memory situation.

              If  this  file  is  set  to  the  value  0,  the kernel's OOM-killer will kill some rogue process.
              Usually, the OOM-killer is able to kill a rogue process and the system will survive.

              If this file is set to the value 1, then the kernel normally panics  when  out-of-memory  happens.
              However,  if  a  process  limits  allocations  to  certain  nodes  using memory policies (mbind(2)
              MPOL_BIND) or cpusets (cpuset(7)) and those nodes reach memory exhaustion status, one process  may
              be  killed  by  the  OOM-killer.  No panic occurs in this case: because other nodes' memory may be
              free, this means the system as a whole may not have reached an out-of-memory situation yet.

              If this file is set to the value 2, the kernel  always  panics  when  an  out-of-memory  condition
              occurs.

              The  default value is 0.  1 and 2 are for failover of clustering.  Select either according to your
              policy of failover.

       /proc/sys/vm/swappiness
              The value in this file controls how aggressively the kernel will swap memory pages.  Higher values
              increase aggressiveness, lower values decrease aggressiveness.  The default value is 60.

       /proc/sys/vm/user_reserve_kbytes (since Linux 3.10)
              Specifies  an amount of memory (in KiB) to reserve for user processes, This is intended to prevent
              a user from starting a single memory hogging process, such that  they  cannot  recover  (kill  the
              hog).   The  value in this file has an effect only when /proc/sys/vm/overcommit_memory is set to 2
              ("overcommit never" mode).  In this case, the system reserves an amount  of  memory  that  is  the
              minimum of [3% of current process size, user_reserve_kbytes].

              The default value in this file is the minimum of [3% of free pages, 128MiB] expressed as KiB.

              If  the value in this file is set to zero, then a user will be allowed to allocate all free memory
              with a single process (minus  the  amount  reserved  by  /proc/sys/vm/admin_reserve_kbytes).   Any
              subsequent attempts to execute a command will result in "fork: Cannot allocate memory".

              Changing the value in this file takes effect whenever an application requests memory.

       /proc/sysrq-trigger (since Linux 2.4.21)
              Writing  a character to this file triggers the same SysRq function as typing ALT-SysRq-<character>
              (see the description of /proc/sys/kernel/sysrq).  This file is normally  writable  only  by  root.
              For  further  details  see  the  Linux  kernel source file Documentation/admin-guide/sysrq.rst (or
              Documentation/sysrq.txt before Linux 4.10).

       /proc/sysvipc
              Subdirectory containing the pseudo-files msg,  sem  and  shm.   These  files  list  the  System  V
              Interprocess  Communication  (IPC)  objects  (respectively: message queues, semaphores, and shared
              memory) that currently exist on the system, providing similar information to  that  available  via
              ipcs(1).   These  files  have  headers  and  are  formatted  (one  IPC  object  per line) for easy
              understanding.  svipc(7) provides further background on the information shown by these files.

       /proc/thread-self (since Linux 3.17)
              This directory refers to the thread accessing the  /proc  filesystem,  and  is  identical  to  the
              /proc/self/task/[tid] directory named by the process thread ID ([tid]) of the same thread.

       /proc/timer_list (since Linux 2.6.21)
              This  read-only  file exposes a list of all currently pending (high-resolution) timers, all clock-
              event sources, and their parameters in a human-readable form.

       /proc/timer_stats (from  Linux 2.6.21 until Linux 4.10)
              This is a debugging facility to make timer (ab)use in a Linux system visible to kernel  and  user-
              space  developers.   It  can be used by kernel and user-space developers to verify that their code
              does not make undue use of timers.  The goal is to avoid unnecessary wakeups,  thereby  optimizing
              power consumption.

              If  enabled  in the kernel (CONFIG_TIMER_STATS), but not used, it has almost zero runtime overhead
              and a relatively small data-structure  overhead.   Even  if  collection  is  enabled  at  runtime,
              overhead is low: all the locking is per-CPU and lookup is hashed.

              The  /proc/timer_stats  file is used both to control sampling facility and to read out the sampled
              information.

              The timer_stats functionality is inactive on bootup.  A sampling period can be started  using  the
              following command:

                  # echo 1 > /proc/timer_stats

              The following command stops a sampling period:

                  # echo 0 > /proc/timer_stats

              The statistics can be retrieved by:

                  $ cat /proc/timer_stats

              While  sampling is enabled, each readout from /proc/timer_stats will see newly updated statistics.
              Once sampling is disabled, the sampled information is kept until a new sample period  is  started.
              This allows multiple readouts.

              Sample output from /proc/timer_stats:

    $ cat /proc/timer_stats
    Timer Stats Version: v0.3
    Sample period: 1.764 s
    Collection: active
      255,     0 swapper/3        hrtimer_start_range_ns (tick_sched_timer)
       71,     0 swapper/1        hrtimer_start_range_ns (tick_sched_timer)
       58,     0 swapper/0        hrtimer_start_range_ns (tick_sched_timer)
        4,  1694 gnome-shell      mod_delayed_work_on (delayed_work_timer_fn)
       17,     7 rcu_sched        rcu_gp_kthread (process_timeout)
    ...
        1,  4911 kworker/u16:0    mod_delayed_work_on (delayed_work_timer_fn)
       1D,  2522 kworker/0:0      queue_delayed_work_on (delayed_work_timer_fn)
    1029 total events, 583.333 events/sec

              The output columns are:

              *  a  count of the number of events, optionally (since Linux 2.6.23) followed by the letter 'D' if
                 this is a deferrable timer;

              *  the PID of the process that initialized the timer;

              *  the name of the process that initialized the timer;

              *  the function where the timer was initialized; and

              *  (in parentheses) the callback function that is associated with the timer.

              During the Linux 4.11 development cycle, this file  was removed because of security  concerns,  as
              it  exposes  information  across  namespaces.   Furthermore,  it  is  possible  to obtain the same
              information via in-kernel tracing facilities such as ftrace.

       /proc/tty
              Subdirectory containing the pseudo-files and subdirectories for tty drivers and line disciplines.

       /proc/uptime
              This file contains two numbers: the uptime of the system (seconds), and the amount of  time  spent
              in idle process (seconds).

       /proc/version
              This  string identifies the kernel version that is currently running.  It includes the contents of
              /proc/sys/kernel/ostype, /proc/sys/kernel/osrelease and /proc/sys/kernel/version.  For example:

        Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6.0)
              This file displays various virtual memory statistics.  Each line of this file  contains  a  single
              name-value  pair,  delimited  by  white  space.   Some  lines  are  present only if the kernel was
              configured with suitable options.  (In some cases, the options required for particular files  have
              changed  across  kernel versions, so they are not listed here.  Details can be found by consulting
              the kernel source code.)  The following fields may be present:

              nr_free_pages (since Linux 2.6.31)

              nr_alloc_batch (since Linux 3.12)

              nr_inactive_anon (since Linux 2.6.28)

              nr_active_anon (since Linux 2.6.28)

              nr_inactive_file (since Linux 2.6.28)

              nr_active_file (since Linux 2.6.28)

              nr_unevictable (since Linux 2.6.28)

              nr_mlock (since Linux 2.6.28)

              nr_anon_pages (since Linux 2.6.18)

              nr_mapped (since Linux 2.6.0)

              nr_file_pages (since Linux 2.6.18)

              nr_dirty (since Linux 2.6.0)

              nr_writeback (since Linux 2.6.0)

              nr_slab_reclaimable (since Linux 2.6.19)

              nr_slab_unreclaimable (since Linux 2.6.19)

              nr_page_table_pages (since Linux 2.6.0)

              nr_kernel_stack (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              nr_unstable (since Linux 2.6.0)

              nr_bounce (since Linux 2.6.12)

              nr_vmscan_write (since Linux 2.6.19)

              nr_vmscan_immediate_reclaim (since Linux 3.2)

              nr_writeback_temp (since Linux 2.6.26)

              nr_isolated_anon (since Linux 2.6.32)

              nr_isolated_file (since Linux 2.6.32)

              nr_shmem (since Linux 2.6.32)
                     Pages used by shmem and tmpfs(5).

              nr_dirtied (since Linux 2.6.37)

              nr_written (since Linux 2.6.37)

              nr_pages_scanned (since Linux 3.17)

              numa_hit (since Linux 2.6.18)

              numa_miss (since Linux 2.6.18)

              numa_foreign (since Linux 2.6.18)

              numa_interleave (since Linux 2.6.18)

              numa_local (since Linux 2.6.18)

              numa_other (since Linux 2.6.18)

              workingset_refault (since Linux 3.15)

              workingset_activate (since Linux 3.15)

              workingset_nodereclaim (since Linux 3.15)

              nr_anon_transparent_hugepages (since Linux 2.6.38)

              nr_free_cma (since Linux 3.7)
                     Number of free CMA (Contiguous Memory Allocator) pages.

              nr_dirty_threshold (since Linux 2.6.37)

              nr_dirty_background_threshold (since Linux 2.6.37)

              pgpgin (since Linux 2.6.0)

              pgpgout (since Linux 2.6.0)

              pswpin (since Linux 2.6.0)

              pswpout (since Linux 2.6.0)

              pgalloc_dma (since Linux 2.6.5)

              pgalloc_dma32 (since Linux 2.6.16)

              pgalloc_normal (since Linux 2.6.5)

              pgalloc_high (since Linux 2.6.5)

              pgalloc_movable (since Linux 2.6.23)

              pgfree (since Linux 2.6.0)

              pgactivate (since Linux 2.6.0)

              pgdeactivate (since Linux 2.6.0)

              pgfault (since Linux 2.6.0)

              pgmajfault (since Linux 2.6.0)

              pgrefill_dma (since Linux 2.6.5)

              pgrefill_dma32 (since Linux 2.6.16)

              pgrefill_normal (since Linux 2.6.5)

              pgrefill_high (since Linux 2.6.5)

              pgrefill_movable (since Linux 2.6.23)

              pgsteal_kswapd_dma (since Linux 3.4)

              pgsteal_kswapd_dma32 (since Linux 3.4)

              pgsteal_kswapd_normal (since Linux 3.4)

              pgsteal_kswapd_high (since Linux 3.4)

              pgsteal_kswapd_movable (since Linux 3.4)

              pgsteal_direct_dma

              pgsteal_direct_dma32 (since Linux 3.4)

              pgsteal_direct_normal (since Linux 3.4)

              pgsteal_direct_high (since Linux 3.4)

              pgsteal_direct_movable (since Linux 2.6.23)

              pgscan_kswapd_dma

              pgscan_kswapd_dma32 (since Linux 2.6.16)

              pgscan_kswapd_normal (since Linux 2.6.5)

              pgscan_kswapd_high

              pgscan_kswapd_movable (since Linux 2.6.23)

              pgscan_direct_dma

              pgscan_direct_dma32 (since Linux 2.6.16)

              pgscan_direct_normal

              pgscan_direct_high

              pgscan_direct_movable (since Linux 2.6.23)

              pgscan_direct_throttle (since Linux 3.6)

              zone_reclaim_failed (since linux 2.6.31)

              pginodesteal (since linux 2.6.0)

              slabs_scanned (since linux 2.6.5)

              kswapd_inodesteal (since linux 2.6.0)

              kswapd_low_wmark_hit_quickly (since 2.6.33)

              kswapd_high_wmark_hit_quickly (since 2.6.33)

              pageoutrun (since Linux 2.6.0)

              allocstall (since Linux 2.6.0)

              pgrotated (since Linux 2.6.0)

              drop_pagecache (since Linux 3.15)

              drop_slab (since Linux 3.15)

              numa_pte_updates (since Linux 3.8)

              numa_huge_pte_updates (since Linux 3.13)

              numa_hint_faults (since Linux 3.8)

              numa_hint_faults_local (since Linux 3.8)

              numa_pages_migrated (since Linux 3.8)

              pgmigrate_success (since Linux 3.8)

              pgmigrate_fail (since Linux 3.8)

              compact_migrate_scanned (since Linux 3.8)

              compact_free_scanned (since Linux 3.8)

              compact_isolated (since Linux 3.8)

              compact_stall (since Linux 2.6.35)
                     See the kernel source file Documentation/vm/transhuge.txt.

              compact_fail (since Linux 2.6.35)
                     See the kernel source file Documentation/vm/transhuge.txt.

              compact_success (since Linux 2.6.35)
                     See the kernel source file Documentation/vm/transhuge.txt.

              htlb_buddy_alloc_success (since Linux 2.6.26)

              htlb_buddy_alloc_fail (since Linux 2.6.26)

              unevictable_pgs_culled (since Linux 2.6.28)

              unevictable_pgs_scanned (since Linux 2.6.28)

              unevictable_pgs_rescued (since Linux 2.6.28)

              unevictable_pgs_mlocked (since Linux 2.6.28)

              unevictable_pgs_munlocked (since Linux 2.6.28)

              unevictable_pgs_cleared (since Linux 2.6.28)

              unevictable_pgs_stranded (since Linux 2.6.28)

              thp_fault_alloc (since Linux 2.6.39)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_fault_fallback (since Linux 2.6.39)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_collapse_alloc (since Linux 2.6.39)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_collapse_alloc_failed (since Linux 2.6.39)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_split (since Linux 2.6.39)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_zero_page_alloc (since Linux 3.8)
                     See the kernel source file Documentation/vm/transhuge.txt.

              thp_zero_page_alloc_failed (since Linux 3.8)
                     See the kernel source file Documentation/vm/transhuge.txt.

              balloon_inflate (since Linux 3.18)

              balloon_deflate (since Linux 3.18)

              balloon_migrate (since Linux 3.18)

              nr_tlb_remote_flush (since Linux 3.12)

              nr_tlb_remote_flush_received (since Linux 3.12)

              nr_tlb_local_flush_all (since Linux 3.12)

              nr_tlb_local_flush_one (since Linux 3.12)

              vmacache_find_calls (since Linux 3.16)

              vmacache_find_hits (since Linux 3.16)

              vmacache_full_flushes (since Linux 3.19)

       /proc/zoneinfo (since Linux 2.6.13)
              This file display information about memory zones.  This is useful  for  analyzing  virtual  memory
              behavior.

NOTES

       Many  strings  (i.e.,  the  environment  and  command  line)  are  in the internal format, with subfields
       terminated by null bytes ('\0'), so you may find that things are more readable if you use  od  -c  or  tr
       "\000" "\n" to read them.  Alternatively, echo `cat <file>` works well.

       This  manual  page  is incomplete, possibly inaccurate, and is the kind of thing that needs to be updated
       very often.

SEE ALSO

       cat(1), dmesg(1), find(1), free(1), init(1), ps(1), tr(1), uptime(1),  chroot(2),  mmap(2),  readlink(2),
       syslog(2),  slabinfo(5),  sysfs(5),  hier(7),  namespaces(7),  time(7),  arp(8),  hdparm(8), ifconfig(8),
       lsmod(8), lspci(8), mount(8), netstat(8), procinfo(8), route(8), sysctl(8)

       The  Linux   kernel   source   files:   Documentation/filesystems/proc.txt   Documentation/sysctl/fs.txt,
       Documentation/sysctl/kernel.txt, Documentation/sysctl/net.txt, and Documentation/sysctl/vm.txt.

COLOPHON

       This  page  is  part  of  release  4.15  of  the  Linux man-pages project.  A description of the project,
       information  about  reporting  bugs,  and  the  latest  version  of  this   page,   can   be   found   at
       https://www.kernel.org/doc/man-pages/.