xfs_check(8)

NAME
xfs_check - check XFS filesystem consistency

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

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

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.

-l  Specifies the device special file where the filesystem's external log resides. Only for those filesystems which use an external log. See the mkfs.xfs -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 structures 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 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
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 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).