xfs_check(8)								xfs_check(8)



NAME
       xfs_check - check XFS filesystem consistency

SYNOPSIS
       xfs_check [ -i ino ] ... [ -b bno ] ... [ -s ] [ -v ] xfs_special

       xfs_check -f [ -i ino ] ... [ -b bno ] ... [ -s ] [ -v ] file

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 xfs_special argu-
       ment, which should be the disk or volume device for the filesystem.  Filesys-
       tems  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.

       The options to xfs_check are:

       -f	Specifies  that	 the  special  device  is  actually  a file (see the
		mkfs.xfs -d file option).  This might happen if an image copy  of  a
		filesystem has been made into an ordinary file.

       -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 a specific inode.  For  instance,  it
		can  be used to locate all the blocks associated with a given inode.

       -b bno	Specifies verbose behavior for a  specific  filesystem	block.	 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) and
		file system blocks may be accomplished using xfs_db's  convert	com-
		mand.

       Any non-verbose output from xfs_check means that the filesystem has an incon-
       sistency.  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
       Under one circumstance, xfs_check unfortunately might dump core	rather	than
       produce	useful output.	If the filesystem is completely corrupt, a core dump
       might be produced instead of the message xxx 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	meaningful  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  alloca-
	      tion group a doesn't match the number of inodes counted in the alloca-
	      tion 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 alloca-
	      tion 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)