Provided by: manpages-dev_3.27-1ubuntu2_all bug

NAME

       mount - mount file system

SYNOPSIS

       #include <sys/mount.h>

       int mount(const char *source, const char *target,
                 const char *filesystemtype, unsigned long mountflags,
                 const void *data);

DESCRIPTION

       mount()  attaches the file system specified by source (which is often a
       device name, but can also be a  directory  name  or  a  dummy)  to  the
       directory specified by target.

       Appropriate privilege (Linux: the CAP_SYS_ADMIN capability) is required
       to mount file systems.

       Since Linux 2.4 a single file system can be visible at  multiple  mount
       points, and multiple mounts can be stacked on the same mount point.

       Values  for  the  filesystemtype  argument  supported by the kernel are
       listed in  /proc/filesystems  (like  "minix",  "ext2",  "ext3",  "jfs",
       "xfs",  "reiserfs",  "msdos",  "proc", "nfs", "iso9660" etc.).  Further
       types may become available when the appropriate modules are loaded.

       The mountflags argument may have the magic number  0xC0ED  (MS_MGC_VAL)
       in  the top 16 bits (this was required in kernel versions prior to 2.4,
       but is no longer required and ignored if specified), and various  mount
       flags   (as  defined  in  <linux/fs.h>  for  libc4  and  libc5  and  in
       <sys/mount.h> for glibc2) in the low order 16 bits:

       MS_BIND (Linux 2.4 onwards)
              Perform a bind mount, making  a  file  or  a  directory  subtree
              visible  at another point within a file system.  Bind mounts may
              cross file system boundaries  and  span  chroot(2)  jails.   The
              filesystemtype  and  data arguments are ignored.  Up until Linux
              2.6.26, mountflags was also ignored (the bind mount has the same
              mount  options  as  the  underlying  mount  point).  Since Linux
              2.6.26, the MS_RDONLY flag is honored when making a bind mount.

       MS_DIRSYNC (since Linux 2.5.19)
              Make directory changes on this file system  synchronous.   (This
              property  can be obtained for individual directories or subtrees
              using chattr(1).)

       MS_MANDLOCK
              Permit  mandatory  locking  on  files  in  this   file   system.
              (Mandatory locking must still be enabled on a per-file basis, as
              described in fcntl(2).)

       MS_MOVE
              Move a subtree.  source specifies an existing  mount  point  and
              target  specifies  the  new location.  The move is atomic: at no
              point is the subtree unmounted.  The filesystemtype, mountflags,
              and data arguments are ignored.

       MS_NOATIME
              Do not update access times for (all types of) files on this file
              system.

       MS_NODEV
              Do not allow access to devices  (special  files)  on  this  file
              system.

       MS_NODIRATIME
              Do  not update access times for directories on this file system.
              This flag provides a subset of  the  functionality  provided  by
              MS_NOATIME; that is, MS_NOATIME implies MS_NODIRATIME.

       MS_NOEXEC
              Do not allow programs to be executed from this file system.

       MS_NOSUID
              Do  not  honor  set-user-ID and set-group-ID bits when executing
              programs from this file system.

       MS_RDONLY
              Mount file system read-only.

       MS_RELATIME (Since Linux 2.6.20)
              When a file on this file system is  accessed,  only  update  the
              file's last access time (atime) if the current value of atime is
              less than or equal to the file's last modification time  (mtime)
              or  last  status change time (ctime).  This option is useful for
              programs, such as mutt(1), that need to know  when  a  file  has
              been  read  since it was last modified.  Since Linux 2.6.30, the
              kernel defaults to the behavior provided by  this  flag  (unless
              MS_NOATIME  was  specified),  and  the  MS_STRICTATIME  flag  is
              required to obtain traditional semantics.   In  addition,  since
              Linux  2.6.30,  the file's last access time is always updated if
              it is more than 1 day old.

       MS_REMOUNT
              Remount an existing  mount.   This  allows  you  to  change  the
              mountflags  and  data  of  an  existing  mount without having to
              unmount and remount the file system.  source and  target  should
              be  the  same  values  specified  in  the  initial mount() call;
              filesystemtype is ignored.

              The   following   mountflags   can   be   changed:    MS_RDONLY,
              MS_SYNCHRONOUS, MS_MANDLOCK; before kernel 2.6.16, the following
              could  also  be  changed:  MS_NOATIME  and  MS_NODIRATIME;  and,
              additionally,  before kernel 2.4.10, the following could also be
              changed: MS_NOSUID, MS_NODEV, MS_NOEXEC.

       MS_SILENT (since Linux 2.6.17)
              Suppress the display of certain (printk()) warning  messages  in
              the  kernel log.  This flag supersedes the misnamed and obsolete
              MS_VERBOSE flag (available since Linux 2.4.12),  which  has  the
              same meaning.

       MS_STRICTATIME (Since Linux 2.6.30)
              Always  update  the  last access time (atime) when files on this
              file system are accessed.  (This was the default behavior before
              Linux  2.6.30.)   Specifying  this  flag overrides the effect of
              setting the MS_NOATIME and MS_RELATIME flags.

       MS_SYNCHRONOUS
              Make writes on this  file  system  synchronous  (as  though  the
              O_SYNC  flag to open(2) was specified for all file opens to this
              file system).

       From Linux 2.4 onwards, the MS_NODEV, MS_NOEXEC,  and  MS_NOSUID  flags
       are  settable  on a per-mount-point basis.  From kernel 2.6.16 onwards,
       MS_NOATIME and MS_NODIRATIME are also  settable  on  a  per-mount-point
       basis.   The  MS_RELATIME  flag  is  also settable on a per-mount-point
       basis.

       The data  argument  is  interpreted  by  the  different  file  systems.
       Typically  it is a string of comma-separated options understood by this
       file system.  See mount(8) for details of  the  options  available  for
       each filesystem type.

RETURN VALUE

       On  success,  zero is returned.  On error, -1 is returned, and errno is
       set appropriately.

ERRORS

       The error values given below result from  filesystem  type  independent
       errors.   Each  filesystem type may have its own special errors and its
       own special behavior.  See the kernel source code for details.

       EACCES A  component  of  a  path  was  not   searchable.    (See   also
              path_resolution(7).)   Or,  mounting  a read-only filesystem was
              attempted without giving the  MS_RDONLY  flag.   Or,  the  block
              device  source  is  located  on  a  filesystem  mounted with the
              MS_NODEV option.

       EBUSY  source is already mounted.  Or, it  cannot  be  remounted  read-
              only,  because  it  still  holds files open for writing.  Or, it
              cannot be mounted on target because target is still busy (it  is
              the  working  directory of some task, the mount point of another
              device, has open files, etc.).

       EFAULT One of the pointer arguments points  outside  the  user  address
              space.

       EINVAL source  had  an  invalid superblock.  Or, a remount (MS_REMOUNT)
              was attempted, but source was not  already  mounted  on  target.
              Or,  a  move (MS_MOVE) was attempted, but source was not a mount
              point, or was '/'.

       ELOOP  Too many links encountered during pathname  resolution.   Or,  a
              move was attempted, while target is a descendant of source.

       EMFILE (In case no block device is required:) Table of dummy devices is
              full.

       ENAMETOOLONG
              A pathname was longer than MAXPATHLEN.

       ENODEV filesystemtype not configured in the kernel.

       ENOENT A pathname was empty or had a nonexistent component.

       ENOMEM The kernel could not allocate a free page to copy  filenames  or
              data into.

       ENOTBLK
              source is not a block device (and a device was required).

       ENOTDIR
              target, or a prefix of source, is not a directory.

       ENXIO  The major number of the block device source is out of range.

       EPERM  The caller does not have the required privileges.

VERSIONS

       The  definitions  of  MS_DIRSYNC,  MS_MOVE,  MS_REC,  MS_RELATIME,  and
       MS_STRICTATIME were only added to glibc headers in version 2.12.

CONFORMING TO

       This function is Linux-specific and should  not  be  used  in  programs
       intended to be portable.

NOTES

       The  original  MS_SYNC flag was renamed MS_SYNCHRONOUS in 1.1.69 when a
       different MS_SYNC was added to <mman.h>.

       Before Linux 2.4 an attempt to execute a  set-user-ID  or  set-group-ID
       program  on  a filesystem mounted with MS_NOSUID would fail with EPERM.
       Since Linux 2.4 the set-user-ID and set-group-ID bits are just silently
       ignored in this case.

   Per-process Namespaces
       Starting   with   kernel   2.4.19,  Linux  provides  per-process  mount
       namespaces.  A mount namespace is the set of file  system  mounts  that
       are  visible  to a process.  Mount-point namespaces can be (and usually
       are) shared between multiple processes, and changes  to  the  namespace
       (i.e.,  mounts  and  unmounts)  by one process are visible to all other
       processes sharing the same namespace.  (The pre-2.4.19 Linux  situation
       can  be  considered  as  one  in which a single namespace was shared by
       every process on the system.)

       A child process created by fork(2) shares its parent's mount namespace;
       the mount namespace is preserved across an execve(2).

       A process can obtain a private mount namespace if: it was created using
       the clone() CLONE_NEWNS flag,  in  which  case  its  new  namespace  is
       initialized  to  be  a copy of the namespace of the process that called
       clone(); or it calls unshare(2) with the CLONE_NEWNS flag, which causes
       the  caller's mount namespace to obtain a private copy of the namespace
       that it was previously sharing with other  processes,  so  that  future
       mounts  and  unmounts  by  the  caller are invisible to other processes
       (except child processes that the caller subsequently creates) and  vice
       versa.

       The  Linux-specific  /proc/PID/mounts  file  exposes  the list of mount
       points in the mount namespace of the process with the specified ID; see
       proc(5) for details.

SEE ALSO

       umount(2), path_resolution(7), mount(8), umount(8)

COLOPHON

       This  page  is  part of release 3.27 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.