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    Command:

    xfs_io

    
    
    

    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 inter-
           faces 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  privi-
                     leges.
    
           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 prealloca-
           tion, 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.
                     -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 cur-
                  rent (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  allo-
                  cating  space  for  the currently open file. If the -R option is
    
           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 sys-
                  tem  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_RAN-
                         DOM), which sets readahead to zero.
                     -s  expect    access    to    data    in   sequential   order
                         (POSIX_FADV_SEQUENTIAL), which doubles the default reada-
                         head on the file.
                     -w  advises   the   specified   data  will  be  needed  again
                         (POSIX_FADV_WILLNEED[*]) which forces the maximum  reada-
                         head.
    
           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  ftrun-
                  cate(2).
    
           sendfile -i srcfile | -f N [ offset length ]
                  On  platforms  which  support it, allows a direct in-kernel copy
    
           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 back-
                  wards  through  the  mapping if the -r option in specified.  The
                  two verbose modes differ only in the relative offsets they  dis-
                  play,  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 speci-
                  fied, 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  map-
                  ping.   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_SEQUEN-
                         TIAL), which doubles the default readahead on the file.
                     -w  advises   the   specified  pages  will  be  needed  again
                         (POSIX_MADV_WILLNEED[*]) which forces the maximum  reada-
                         head.
    
           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 avail-
                  able 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 path-
    
                                                                         xfs_io(8)
    
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