xfs_repair(8) System Manager's Manual xfs_repair(8)
NAME
xfs_repair - repair an XFS filesystem
SYNOPSIS
xfs_repair [ -dfLPv ] [ -n | -e ] [ -m maxmem ] [ -c subopt=value ] [
-o subopt[=value] ] [ -t interval ] [ -l logdev ] [ -r rtdev ] device
xfs_repair -V
DESCRIPTION
xfs_repair repairs corrupt or damaged XFS filesystems (see xfs(5)).
The filesystem is specified using the device argument which should be
the device name of the disk partition or volume containing the filesys-
tem. If given the name of a block device, xfs_repair will attempt to
find the raw device associated with the specified block device and will
use the raw device instead.
Regardless, the filesystem to be repaired must be unmounted, otherwise,
the resulting filesystem may be inconsistent or corrupt.
OPTIONS
-f Specifies that the filesystem image to be processed is stored in
a regular file at device (see the mkfs.xfs -d file option). This
might happen if an image copy of a filesystem has been copied or
written into an ordinary file. This option implies that any
external log or realtime section is also in an ordinary file.
-L Force Log Zeroing. Forces xfs_repair to zero the log even if it
is dirty (contains metadata changes). When using this option
the filesystem will likely appear to be corrupt, and can cause
the loss of user files and/or data. See the DIRTY LOGS section
for more information.
-l logdev
Specifies the device special file where the filesystem's exter-
nal log resides. Only for those filesystems which use an exter-
nal log. See the mkfs.xfs -l option, and refer to xfs(5) for a
detailed description of the XFS log.
-r rtdev
Specifies the device special file where the filesystem's real-
time section resides. Only for those filesystems which use a
realtime section. See the mkfs.xfs -r option, and refer to
xfs(5) for a detailed description of the XFS realtime section.
-n No modify mode. Specifies that xfs_repair should not modify the
filesystem but should only scan the filesystem and indicate what
repairs would have been made. This option cannot be used
together with -e.
-P Disable prefetching of inode and directory blocks. Use this
option if you find xfs_repair gets stuck and stops proceeding.
Interrupting a stuck xfs_repair is safe.
-m maxmem
Specifies the approximate maximum amount of memory, in
megabytes, to use for xfs_repair. xfs_repair has its own inter-
nal block cache which will scale out up to the lesser of the
process's virtual address limit or about 75% of the system's
physical RAM. This option overrides these limits.
NOTE: These memory limits are only approximate and may use more
than the specified limit.
-c subopt=value
Change filesystem parameters. Refer to xfs_admin(8) for informa-
tion on changing filesystem parameters.
-o subopt[=value]
Override what the program might conclude about the filesystem if
left to its own devices.
The suboptions supported are:
bhash=bhashsize
overrides the default buffer cache hash size. The
total number of buffer cache entries are limited to 8
times this amount. The default size is set to use up
the remainder of 75% of the system's physical RAM
size.
ag_stride=ags_per_concat_unit
This creates additional processing threads to parallel
process AGs that span multiple concat units. This can
significantly reduce repair times on concat based
filesystems.
force_geometry
Check the filesystem even if geometry information
could not be validated. Geometry information can not
be validated if only a single allocation group exists
and thus we do not have a backup superblock available,
or if there are two allocation groups and the two
superblocks do not agree on the filesystem geometry.
Only use this option if you validated the geometry
yourself and know what you are doing. If In doubt run
in no modify mode first.
-t interval
Modify reporting interval, specified in seconds. During long
runs xfs_repair outputs its progress every 15 minutes. Reporting
is only activated when ag_stride is enabled.
-v Verbose output. May be specified multiple times to increase
verbosity.
-d Repair dangerously. Allow xfs_repair to repair an XFS filesystem
mounted read only. This is typically done on a root filesystem
from single user mode, immediately followed by a reboot.
-e If any metadata corruption was repaired, the status returned is
4 instead of the usual 0. This option cannot be used together
with -n.
-V Prints the version number and exits.
Checks Performed
Inconsistencies corrected include the following:
1. Inode and inode blockmap (addressing) checks: bad magic number
in inode, bad magic numbers in inode blockmap blocks, extents
out of order, incorrect number of records in inode blockmap
blocks, blocks claimed that are not in a legal data area of the
filesystem, blocks that are claimed by more than one inode.
2. Inode allocation map checks: bad magic number in inode map
blocks, inode state as indicated by map (free or in-use) incon-
sistent with state indicated by the inode, inodes referenced by
the filesystem that do not appear in the inode allocation map,
inode allocation map referencing blocks that do not appear to
contain inodes.
3. Size checks: number of blocks claimed by inode inconsistent with
inode size, directory size not block aligned, inode size not
consistent with inode format.
4. Directory checks: bad magic numbers in directory blocks, incor-
rect number of entries in a directory block, bad freespace
information in a directory leaf block, entry pointing to an
unallocated (free) or out of range inode, overlapping entries,
missing or incorrect dot and dotdot entries, entries out of
hashvalue order, incorrect internal directory pointers, direc-
tory type not consistent with inode format and size.
5. Pathname checks: files or directories not referenced by a path-
name starting from the filesystem root, illegal pathname compo-
nents.
6. Link count checks: link counts that do not agree with the number
of directory references to the inode.
7. Freemap checks: blocks claimed free by the freemap but also
claimed by an inode, blocks unclaimed by any inode but not
appearing in the freemap.
8. Super Block checks: total free block and/or free i-node count
incorrect, filesystem geometry inconsistent, secondary and pri-
mary superblocks contradictory.
Orphaned files and directories (allocated, in-use but unreferenced) are
reconnected by placing them in the lost+found directory. The name
assigned is the inode number.
Disk Errors
xfs_repair aborts on most disk I/O errors. Therefore, if you are trying
to repair a filesystem that was damaged due to a disk drive failure,
steps should be taken to ensure that all blocks in the filesystem are
readable and writable before attempting to use xfs_repair to repair the
filesystem. A possible method is using dd(8) to copy the data onto a
good disk.
lost+found
The directory lost+found does not have to already exist in the filesys-
tem being repaired. If the directory does not exist, it is automati-
cally created if required. If it already exists, it will be checked
for consistency and if valid will be used for additional orphaned
files. Invalid lost+found directories are removed and recreated. Exist-
ing files in a valid lost+found are not removed or renamed.
Corrupted Superblocks
XFS has both primary and secondary superblocks. xfs_repair uses infor-
mation in the primary superblock to automatically find and validate the
primary superblock against the secondary superblocks before proceeding.
Should the primary be too corrupted to be useful in locating the sec-
ondary superblocks, the program scans the filesystem until it finds and
validates some secondary superblocks. At that point, it generates a
primary superblock.
Quotas
If quotas are in use, it is possible that xfs_repair will clear some or
all of the filesystem quota information. If so, the program issues a
warning just before it terminates. If all quota information is lost,
quotas are disabled and the program issues a warning to that effect.
Note that xfs_repair does not check the validity of quota limits. It is
recommended that you check the quota limit information manually after
xfs_repair. Also, space usage information is automatically regenerated
the next time the filesystem is mounted with quotas turned on, so the
next quota mount of the filesystem may take some time.
DIAGNOSTICS
xfs_repair issues informative messages as it proceeds indicating what
it has found that is abnormal or any corrective action that it has
taken. Most of the messages are completely understandable only to
those who are knowledgeable about the structure of the filesystem.
Some of the more common messages are explained here. Note that the
language of the messages is slightly different if xfs_repair is run in
no-modify mode because the program is not changing anything on disk.
No-modify mode indicates what it would do to repair the filesystem if
run without the no-modify flag.
disconnected inode ino, moving to lost+found
An inode numbered ino was not connected to the filesystem direc-
tory tree and was reconnected to the lost+found directory. The
inode is assigned the name of its inode number (ino). If a
lost+found directory does not exist, it is automatically cre-
ated.
disconnected dir inode ino, moving to lost+found
As above only the inode is a directory inode. If a directory
inode is attached to lost+found, all of its children (if any)
stay attached to the directory and therefore get automatically
reconnected when the directory is reconnected.
imap claims in-use inode ino is free, correcting imap
The inode allocation map thinks that inode ino is free whereas
examination of the inode indicates that the inode may be in use
(although it may be disconnected). The program updates the
inode allocation map.
imap claims free inode ino is in use, correcting imap
The inode allocation map thinks that inode ino is in use whereas
examination of the inode indicates that the inode is not in use
and therefore is free. The program updates the inode allocation
map.
resetting inode ino nlinks from x to y
The program detected a mismatch between the number of valid
directory entries referencing inode ino and the number of refer-
ences recorded in the inode and corrected the the number in the
inode.
fork-type fork in ino ino claims used block bno
Inode ino claims a block bno that is used (claimed) by either
another inode or the filesystem itself for metadata storage. The
fork-type is either data or attr indicating whether the problem
lies in the portion of the inode that tracks regular data or the
portion of the inode that stores XFS attributes. If the inode
is a real-time (rt) inode, the message says so. Any inode that
claims blocks used by the filesystem is deleted. If two or more
inodes claim the same block, they are both deleted.
fork-type fork in ino ino claims dup extent ...
Inode ino claims a block in an extent known to be claimed more
than once. The offset in the inode, start and length of the
extent is given. The message is slightly different if the inode
is a real-time (rt) inode and the extent is therefore a real-
time (rt) extent.
inode ino - bad extent ...
An extent record in the blockmap of inode ino claims blocks that
are out of the legal range of the filesystem. The message sup-
plies the start, end, and file offset of the extent. The mes-
sage is slightly different if the extent is a real-time (rt)
extent.
bad fork-type fork in inode ino
There was something structurally wrong or inconsistent with the
data structures that map offsets to filesystem blocks.
cleared inode ino
There was something wrong with the inode that was uncorrectable
so the program freed the inode. This usually happens because
the inode claims blocks that are used by something else or the
inode itself is badly corrupted. Typically, this message is pre-
ceded by one or more messages indicating why the inode needed to
be cleared.
bad attribute fork in inode ino, clearing attr fork
There was something wrong with the portion of the inode that
stores XFS attributes (the attribute fork) so the program reset
the attribute fork. As a result of this, all attributes on that
inode are lost.
correcting nextents for inode ino, was x - counted y
The program found that the number of extents used to store the
data in the inode is wrong and corrected the number. The mes-
sage refers to nextents if the count is wrong on the number of
extents used to store attribute information.
entry name in dir dir_ino not consistent with .. value (xxxx) in dir
ino ino, junking entry name in directory inode dir_ino
The entry name in directory inode dir_ino references a directory
inode ino. However, the .. entry in directory ino does not
point back to directory dir_ino, so the program deletes the
entry name in directory inode dir_ino. If the directory inode
ino winds up becoming a disconnected inode as a result of this,
it is moved to lost+found later.
entry name in dir dir_ino references already connected dir ino ino,
junking entry name in directory inode dir_ino
The entry name in directory inode dir_ino points to a directory
inode ino that is known to be a child of another directory.
Therefore, the entry is invalid and is deleted. This message
refers to an entry in a small directory. If this were a large
directory, the last phrase would read "will clear entry".
entry references free inode ino in directory dir_ino, will clear entry
An entry in directory inode dir_ino references an inode ino that
is known to be free. The entry is therefore invalid and is
deleted. This message refers to a large directory. If the
directory were small, the message would read "junking entry
...".
EXIT STATUS
xfs_repair -n (no modify mode) will return a status of 1 if filesystem
corruption was detected and 0 if no filesystem corruption was detected.
xfs_repair run without the -n option will always return a status code
of 0 if it completes without problems, unless the flag -e is used. If
it is used, then status 4 is reported when any issue with the filesys-
tem was found, but could be fixed. If a runtime error is encountered
during operation, it will return a status of 1. In this case,
xfs_repair should be restarted. If xfs_repair is unable to proceed due
to a dirty log, it will return a status of 2. See below.
DIRTY LOGS
Due to the design of the XFS log, a dirty log can only be replayed by
the kernel, on a machine having the same CPU architecture as the
machine which was writing to the log. xfs_repair cannot replay a dirty
log and will exit with a status code of 2 when it detects a dirty log.
In this situation, the log can be replayed by mounting and immediately
unmounting the filesystem on the same class of machine that crashed.
Please make sure that the machine's hardware is reliable before replay-
ing to avoid compounding the problems.
If mounting fails, the log can be erased by running xfs_repair with the
-L option. All metadata updates in progress at the time of the crash
will be lost, which may cause significant filesystem damage. This
should only be used as a last resort.
BUGS
The filesystem to be checked and repaired must have been unmounted
cleanly using normal system administration procedures (the umount(8)
command or system shutdown), not as a result of a crash or system
reset. If the filesystem has not been unmounted cleanly, mount it and
unmount it cleanly before running xfs_repair.
xfs_repair does not do a thorough job on XFS extended attributes. The
structure of the attribute fork will be consistent, but only the con-
tents of attribute forks that will fit into an inode are checked. This
limitation will be fixed in the future.
The no-modify mode (-n option) is not completely accurate. It does not
catch inconsistencies in the freespace and inode maps, particularly
lost blocks or subtly corrupted maps (trees).
The no-modify mode can generate repeated warnings about the same prob-
lems because it cannot fix the problems as they are encountered.
If a filesystem fails to be repaired, a metadump image can be generated
with xfs_metadump(8) and be sent to an XFS maintainer to be analysed
and xfs_repair fixed and/or improved.
SEE ALSO
dd(1), mkfs.xfs(8), umount(8), xfs_admin(8), xfs_metadump(8), xfs(5).
xfs_repair(8)
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