xfs_check(8)						      System Manager's Manual						      xfs_check(8)

NAME

       xfs_check - check XFS filesystem consistency

SYNOPSIS

       xfs_check [ -i ino ] ... [ -b bno ] ... [ -f ] [ -s ] [ -v ] [ -l logdev ] device

DESCRIPTION

       xfs_check  checks whether an XFS filesystem is consistent.  It is normally run only when there is reason to believe that the filesystem has
       a consistency problem.  The filesystem to be checked is specified by the device argument, which should be the disk or volume device for the
       filesystem.   Filesystems  stored in files can also be checked, using the -f flag. The filesystem should normally be unmounted or read-only
       during the execution of xfs_check.  Otherwise, spurious problems are reported.

OPTIONS

       -f     Specifies that the filesystem image to be processed is stored in a regular file at device (see the mkfs.xfs(8) -d file option). This
	      might happen if an image copy of a filesystem has been made into an ordinary file.

       -l logdev
	      Specifies  the  device  where  the filesystem's external log resides.  Only for those filesystems which use an external log. See the
	      mkfs.xfs(8) -l option, and refer to xfs(5) for a detailed description of the XFS log.

       -s     Specifies that only serious errors should be reported.  Serious errors are those that make it impossible to find major  data  struc-
	      tures  in  the filesystem. This option can be used to cut down the amount of output when there is a serious problem, when the output
	      might make it difficult to see what the real problem is.

       -v     Specifies verbose output; it is impossibly long for a reasonably-sized filesystem.  This option is intended for internal use only.

       -i ino Specifies verbose behavior for the specified inode ino.  For instance, it can be used to locate all the  blocks  associated  with  a
	      given inode.

       -b bno Specifies  verbose  behavior  for  the  specific filesystem block at bno.  For instance, it can be used to determine what a specific
	      block is used for. The block number is a "file system block number".  Conversion between disk addresses (i.e. addresses reported	by
	      xfs_bmap(8)) and file system blocks may be accomplished using xfs_db(8)'s convert command.

       Any  output  that  is produced when xfs_check is not run in verbose mode indicates that the filesystem has an inconsistency. The filesystem
       can be repaired using either xfs_repair(8) to fix the filesystem in place, or by using xfsdump(8) and mkfs.xfs(8) to dump  the  filesystem,
       make  a	new  filesystem,  then	use  xfsrestore(8)  to	restore the data onto the new filesystem.  Note that xfsdump may fail on a corrupt
       filesystem.  However, if the filesystem is mountable, xfsdump can be used to try and save important data before	repairing  the	filesystem
       with xfs_repair.  If the filesystem is not mountable though, xfs_repair is the only viable option.

DIAGNOSTICS

       If the filesystem is completely corrupt, a core dump might be produced instead of the message
	      device is not a valid filesystem

       If the filesystem is very large (has many files) then xfs_check might run out of memory. In this case the message
	      out of memory
       is printed.

       The following is a description of the most likely problems and the associated messages.	Most of the diagnostics produced are only meaning-
       ful with an understanding of the structure of the filesystem.

       agf_freeblks n, counted m in ag a
	      The freeblocks count in the allocation group header for allocation group a doesn't match the number of blocks counted free.

       agf_longest n, counted m in ag a
	      The longest free extent in the allocation group header for allocation group a doesn't match the longest free  extent  found  in  the
	      allocation group.

       agi_count n, counted m in ag a
	      The  allocated  inode  count in the allocation group header for allocation group a doesn't match the number of inodes counted in the
	      allocation group.

       agi_freecount n, counted m in ag a
	      The free inode count in the allocation group header for allocation group a doesn't match the number of inodes counted  free  in  the
	      allocation group.

       block a/b expected inum 0 got i
	      The  block number is specified as a pair (allocation group number, block in the allocation group).  The block is used multiple times
	      (shared), between multiple inodes.  This message usually follows a message of the next type.

       block a/b expected type unknown got y
	      The block is used multiple times (shared).

       block a/b type unknown not expected
	      The block is unaccounted for (not in the freelist and not in use).

       link count mismatch for inode nnn (name xxx), nlink m, counted n
	      The inode has a bad link count (number of references in directories).

       rtblock b expected inum 0 got i
	      The block is used multiple times (shared), between multiple inodes.  This message usually follows a message of the next type.

       rtblock b expected type unknown got y
	      The real-time block is used multiple times (shared).

       rtblock b type unknown not expected
	      The real-time block is unaccounted for (not in the freelist and not in use).

       sb_fdblocks n, counted m
	      The number of free data blocks recorded in the superblock doesn't match the number counted free in the filesystem.

       sb_frextents n, counted m
	      The number of free real-time extents recorded in the superblock doesn't match the number counted free in the filesystem.

       sb_icount n, counted m
	      The number of allocated inodes recorded in the superblock doesn't match the number allocated in the filesystem.

       sb_ifree n, counted m
	      The number of free inodes recorded in the superblock doesn't match the number free in the filesystem.

SEE ALSO

       mkfs.xfs(8), xfsdump(8), xfsrestore(8), xfs_ncheck(8), xfs_repair(8), xfs(5).

																      xfs_check(8)