Provided by: xfsprogs_3.1.7_amd64 bug

NAME

       xfs_io - debug the I/O path of an XFS filesystem

SYNOPSIS

       xfs_io [ -adFfmrRstx ] [ -c cmd ] ... [ -p prog ] file

DESCRIPTION

       xfs_io  is a debugging tool like xfs_db(8), but is aimed at examining the regular file I/O
       paths rather than the raw XFS volume itself.   These  code  paths  include  not  only  the
       obvious  read/write/mmap  interfaces for manipulating files, but also cover all of the XFS
       extensions (such as space preallocation, additional inode flags, etc).

OPTIONS

       -c cmd    xfs_io commands may be run interactively (the default) or as  arguments  on  the
                 command  line.  Multiple  -c arguments may be given. The commands are run in the
                 sequence given, then the program exits.

       -p prog   Set the program name for prompts and some error messages, the default  value  is
                 xfs_io.

       -F        Allow  file  to  reside  in  non-XFS  (foreign)  filesystems.   This  mode has a
                 restricted set of commands.

       -f        Create file if it does not already exist.

       -r        Open file read-only, initially. This is required if file is immutable or append-
                 only.

       -x        Expert mode. Dangerous commands are only available in this mode.  These commands
                 also tend to require additional privileges.

       The other open(2) options described below are also available from the command line.

CONCEPTS

       xfs_io maintains a number of open files and  memory  mappings.   Files  can  be  initially
       opened on the command line (optionally), and additional files can also be opened later.

       xfs_io  commands  can  be  broken  up into three groups.  Some commands are aimed at doing
       regular file I/O - read, write, sync, space preallocation, etc.

       The second set of commands exist for manipulating  memory  mapped  regions  of  a  file  -
       mapping, accessing, storing, unmapping, flushing, etc.

       The  remaining  commands are for the navigation and display of data structures relating to
       the open files, mappings, and the filesystems where they reside.

       Many commands have extensive online help. Use the help command for  more  details  on  any
       command.

FILE I/O COMMANDS

       file [ N ]
              Display  a  list  of all open files and (optionally) switch to an alternate current
              open file.

       open [[ -FacdfrstR ] path ]
              Closes the current file, and opens the file specified by path instead. Without  any
              arguments, displays statistics about the current file - see the stat command.
                 -F  allows  non-XFS  (foreign)  files  to  be  opened  and  operated  on  with a
                     restricted command set.
                 -a  opens append-only (O_APPEND).
                 -d  opens for direct I/O (O_DIRECT).
                 -f  creates the file if it doesn't already exist (O_CREAT).
                 -r  opens read-only (O_RDONLY).
                 -s  opens for synchronous I/O (O_SYNC).
                 -t  truncates on open (O_TRUNC).
                 -R  marks the file as a realtime XFS file after opening it, if it is not already
                     marked as such.

       o      See the open command.

       close  Closes  the  current  open  file,  marking  the  next  open file as current (if one
              exists).

       c      See the close command.

       pread [ -b bsize ] [ -v ] offset length
              Reads a range of bytes in a specified blocksize from the given offset.
                 -b  can be used to set the blocksize into which the  read(2)  requests  will  be
                     split. The default blocksize is 4096 bytes.
                 -v  dump  the contents of the buffer after reading, by default only the count of
                     bytes actually read is dumped.

       r      See the pread command.

       pwrite [ -i file ] [ -d ] [ -s skip ] [ -b size ] [ -S seed ] offset length
              Writes a range of bytes in a specified blocksize from the given offset.  The  bytes
              written can be either a set pattern or read in from another file before writing.
                 -i  allows  an  input  file  to  be  specified  as  the source of the data to be
                     written.
                 -d  causes direct I/O, rather than the usual  buffered  I/O,  to  be  used  when
                     reading the input file.
                 -s  specifies  the  number  of  bytes  to  skip from the start of the input file
                     before starting to read.
                 -b  used to set the blocksize into which the write(2) requests  will  be  split.
                     The default blocksize is 4096 bytes.
                 -S  used to set the (repeated) fill pattern which is used when the data to write
                     is not coming from a  file.   The  default  buffer  fill  pattern  value  is
                     0xcdcdcdcd.

       w      See the pwrite command.

       bmap [ -adlpv ] [ -n nx ]
              Prints the block mapping for the current open file. Refer to the xfs_bmap(8) manual
              page for complete documentation.

       extsize [ -R | -D ] [ value ]
              Display and/or modify the preferred extent size used when allocating space for  the
              currently  open  file.  If  the  -R  option  is  specified,  a recursive descent is
              performed for all directory entries below the currently open file (-D can  be  used
              to  restrict  the  output to directories only).  If the target file is a directory,
              then the inherited extent size is set for that directory (new files created in that
              directory  inherit  that  extent size).  The value should be specified in bytes, or
              using one of the usual units suffixes (k, m, g, b, etc). The extent size is  always
              reported in units of bytes.

       allocsp size 0
              Sets  the  size of the file to size and zeroes any additional space allocated using
              the XFS_IOC_ALLOCSP/XFS_IOC_FREESP system call described in  the  xfsctl(3)  manual
              page.  allocsp and freesp do exactly the same thing.

       freesp size 0
              See the allocsp command.

       fadvise [ -r | -s | [[ -d | -n | -w ] offset length ]]
              On  platforms  which  support it, allows hints be given to the system regarding the
              expected I/O patterns on the file.  The range arguments are required by some advise
              commands  ([*]  below),  and  the  others  must  have  no range arguments.  With no
              arguments, the POSIX_FADV_NORMAL advice is implied (default readahead).
                 -d  the   data   will   not   be   accessed   again   in   the    near    future
                     (POSIX_FADV_DONTNEED[*]).
                 -n  data will be accessed once and not be reused (POSIX_FADV_NOREUSE[*]).
                 -r  expect  access  to  data  in  random  order  (POSIX_FADV_RANDOM), which sets
                     readahead to zero.
                 -s  expect access to data in  sequential  order  (POSIX_FADV_SEQUENTIAL),  which
                     doubles the default readahead on the file.
                 -w  advises  the  specified  data  will be needed again (POSIX_FADV_WILLNEED[*])
                     which forces the maximum readahead.

       fdatasync
              Calls fdatasync(2) to flush the file's in-core data to disk.

       fsync  Calls fsync(2) to flush all in-core file state to disk.

       s      See the fsync command.

       resvsp offset length
              Allocates reserved, unwritten space for part of a  file  using  the  XFS_IOC_RESVSP
              system call described in the xfsctl(3) manual page.

       unresvsp offset length
              Frees  reserved  space  for  part  of a file using the XFS_IOC_UNRESVSP system call
              described in the xfsctl(3) manual page.

       falloc [ -k ] offset length
              Allocates reserved, unwritten space for part of a file using the fallocate  routine
              as described in the fallocate(3) manual page.
                 -k  will set the FALLOC_FL_KEEP_SIZE flag as described in fallocate(3).

       truncate offset
              Truncates the current file at the given offset using ftruncate(2).

       sendfile -i srcfile | -f N [ offset length ]
              On  platforms  which  support  it,  allows a direct in-kernel copy between two file
              descriptors. The current open file is the target, the source must be  specified  as
              another open file (-f) or by path (-i).

MEMORY MAPPED I/O COMMANDS

       mmap [ N | [[ -rwx ] offset length ]]
              With  no  arguments,  mmap  shows the current mappings. Specifying a single numeric
              argument N sets the current mapping.  If  two  arguments  are  specified  (a  range
              specified  by  offset and length), a new mapping is created spanning the range, and
              the protection mode can be given as a combination  of  PROT_READ  (-r),  PROT_WRITE
              (-w), and PROT_EXEC (-x).

       mm     See the mmap command.

       munmap Unmaps the current memory mapping.

       mu     See the munmap command.

       mread [ -f | -v ] [ -r ] [ offset length ]
              Accesses  a  segment  of  the  current memory mapping, optionally dumping it to the
              standard output stream (with -v or -f option)  for  inspection.  The  accesses  are
              performed  sequentially from the start offset by default, but can also be done from
              the end backwards through the mapping if the  -r  option  in  specified.   The  two
              verbose  modes  differ  only in the relative offsets they display, the -f option is
              relative to file start, whereas -v shows offsets  relative  to  the  start  of  the
              mapping.

       mr     See the mread command.

       mwrite [ -r ] [ -S seed ] [ offset length ]
              Stores  a  byte into memory for a range within a mapping.  The default stored value
              is 'X', repeated to fill the range specified, but this can be changed using the  -S
              option.   The  memory  stores  are  performed sequentially from the start offset by
              default, but can also be done from the end backwards through the mapping if the  -r
              option in specified.

       mw     See the mwrite command.

       msync [ -i ] [ -a | -s ] [ offset length ]
              Writes  all modified copies of pages over the specified range (or entire mapping if
              no  range  specified)  to  their  backing  storage  locations.   Also,   optionally
              invalidates  (-i)  so that subsequent references to the pages will be obtained from
              their backing storage locations (instead of cached copies).  The flush can be  done
              synchronously (-s) or asynchronously (-a).

       ms     See the msync command.

       madvise [ -d | -r | -s | -w ] [ offset length ]
              Modifies  page  cache  behavior  when  operating on the current mapping.  The range
              arguments are required by some advise commands ([*] below).  With no arguments, the
              POSIX_MADV_NORMAL advice is implied (default readahead).
                 -d  the pages will not be needed (POSIX_MADV_DONTNEED[*]).
                 -r  expect  random  page references (POSIX_MADV_RANDOM), which sets readahead to
                     zero.
                 -s  expect sequential page references (POSIX_MADV_SEQUENTIAL), which doubles the
                     default readahead on the file.
                 -w  advises  the  specified  pages will be needed again (POSIX_MADV_WILLNEED[*])
                     which forces the maximum readahead.

       mincore
              Dumps a list of pages or ranges of pages  that  are  currently  in  core,  for  the
              current memory mapping.

OTHER COMMANDS

       print  Display  a  list of all open files and memory mapped regions.  The current file and
              current mapping are distinguishable from any others.

       p      See the print command.

       quit   Exit xfs_io.

       q      See the quit command.

       lsattr [ -R | -D | -a | -v ]
              List extended inode flags  on  the  currently  open  file.  If  the  -R  option  is
              specified,  a  recursive  descent  is performed for all directory entries below the
              currently open file (-D can be used to restrict the output  to  directories  only).
              This  is  a  depth  first descent, it does not follow symlinks and it also does not
              cross mount points.

       chattr [ -R | -D ] [ +/-riasAdtPneEfS ]
              Change extended inode flags on the currently open file. The -R and -D options  have
              the  same  meaning  as  above.  The mapping between each letter and the inode flags
              (refer to xfsctl(3) for the full list) is available via the help command.

       freeze Suspend all write I/O requests  to  the  filesystem  of  the  current  file.   Only
              available in expert mode and requires privileges.

       thaw   Undo  the  effects of a filesystem freeze operation.  Only available in expert mode
              and requires privileges.

       inject [ tag ]
              Inject errors into a filesystem to observe filesystem behavior at  specific  points
              under adverse conditions. Without the tag argument, displays the list of error tags
              available.  Only available in expert mode and requires privileges.

       resblks [ blocks ]
              Get and/or set count of reserved filesystem blocks using the XFS_IOC_GET_RESBLKS or
              XFS_IOC_SET_RESBLKS system calls.  Note -- this can be useful for exercising out of
              space behavior.  Only available in expert mode and requires privileges.

       shutdown [ -f ]
              Force the filesystem  to  shutdown  (with  or  without  flushing  the  log).   Only
              available in expert mode and requires privileges.

       stat [ -v ]
              Selected  statistics  from  stat(2)  and  the  XFS_IOC_GETXATTR  system call on the
              current file. If the -v option is specified, the atime (last access),  mtime  (last
              modify), and ctime (last change) timestamps are also displayed.

       statfs Selected  statistics  from  statfs(2) and the XFS_IOC_FSGEOMETRY system call on the
              filesystem where the current file resides.

       parent [ -cpv ]
              By default this command prints out  the  parent  inode  numbers,  inode  generation
              numbers  and basenames of all the hardlinks which point to the inode of the current
              file.
                 -p  the output is similar to the default  output  except  pathnames  up  to  the
                     mount-point are printed out instead of the component name.
                 -c  the file's filesystem will check all the parent attributes for consistency.
                 -v  verbose output will be printed.
              [NOTE: Not currently operational on Linux.]

SEE ALSO

       mkfs.xfs(8),   xfsctl(3),   xfs_bmap(8),   xfs_db(8),   xfs(5),   fdatasync(2),  fstat(2),
       fstatfs(2), fsync(2), ftruncate(2), mmap(2), msync(2), open(2), pread(2), pwrite(2).

                                                                                        xfs_io(8)