man xfs_repair (Administration système) - repair an XFS filesystem

NAME

xfs_repair - repair an XFS filesystem

SYNOPSIS

xfs_repair [ -nLvVd ] [ -o subopt[=value] ]
	[-l logdev] [-r rtdev] xfs_special

xfs_repair -f [ -nLvVd ] [ -o subopt[=value] ]
	[-l logfile] [-r rtfile] file

DESCRIPTION

xfs_repair repairs corrupt or damaged XFS filesystems (see xfs(5)). The filesystem is specified using the xfs_special argument which should be the device name of the disk partition or volume containing the filesystem. 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.

The options to xfs_repair 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 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.
-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.
-r: Specifies the device special file where the filesystem's realtime 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.
-o: Override what the program might conclude about the filesystem if left to its own devices.
The assume_xfs suboption specifies that the filesystem is an XFS filesystem. Normally, if xfs_repair cannot find an XFS superblock, it checks to see if the filesystem is an EFS filesystem before it tries to regenerate the XFS superblock. If the assume_xfs option is in effect, xfs_repair will assume that the filesystem is an XFS filesystem and will ignore an EFS superblock if one is found.
-v: Verbose output.
-d: Repair dangerously. Allow xfs_repair to repair an XFS filesystem mounted read only. This is typically done on a root fileystem from single user mode, immediately followed by a reboot.

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) inconsistent 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, incorrect 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, directory type not consistent with inode format and size.
5.: Pathname checks: files or directories not referenced by a pathname starting from the filesystem root, illegal pathname components.
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 primary 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 writeable 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 filesystem being repaired. If the directory does not exist, it is automatically created. If the lost+found directory already exists, the lost+found directory is deleted and recreated every time xfs_repair runs. This ensures that there are no name conflicts in lost+found. However, if you rename a file in lost+found and leave it there, if xfs_repair is run again, that file is renamed back to its inode number.

Corrupted Superblocks

XFS has both primary and secondary superblocks. xfs_repair uses information 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 secondary 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 xxxx, moving to lost+found

An inode numbered xxxx was not connected to the filesystem directory tree and was reconnected to the lost+found directory. The inode is assigned the name of its inode number (i-number). If a lost+found directory does not exist, it is automatically created.

disconnected dir inode xxxx, 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 xxxx is free, correcting imap

The inode allocation map thinks that inode xxxx 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 xxxx is in use, correcting imap

The inode allocation map thinks that inode xxxx 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 xxxx nlinks from x to y

The program detected a mismatch between the number of valid directory entries referencing inode xxxx and the number of references recorded in the inode and corrected the the number in the inode.

fork-type fork in ino xxxx claims used block yyyy

Inode xxxx claims a block yyyy 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 xxxx claims dup extent ...

Inode xxxx 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 xxxx - bad extent ...

An extent record in the blockmap of inode xxxx claims blocks that are out of the legal range of the filesystem. The message supplies the start, end, and file offset of the extent. The message is slightly different if the extent is a real-time (rt) exent.

bad fork-type fork in inode xxxx

There was something structurally wrong or inconsistent with the data structures that map offsets to filesystem blocks.

cleared inode xxxx

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 preceded by one or more messages indicating why the inode needed to be cleared.

bad attribute fork in inode xxxx, 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 xxxx, 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 message refers to nextents if the count is wrong on the number of extents used to store attribute information.

entry "name" in dir xxxx not consistent with .. value (yyyy) in dir ino xxxx, junking entry "name" in directory inode xxxx

The entry "name" in directory inode xxxx references a directory inode yyyy. However, the .. entry in directory yyyy does not point back to directory xxxx, so the program deletes the entry "name" in directory inode xxxx. If the directory inode yyyy winds up becoming a disconnected inode as a result of this, it is moved to lost+found later.

entry "name" in dir xxxx references already connected dir ino yyyy, junking entry "name" in directory inode xxxx

The entry "name" in directory inode xxxx points to a directory inode yyyy 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 xxxx in directory yyyy, will clear entry

An entry in directory inode yyyy references an inode xxxx 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 node) 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.

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 contents 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 problems because it cannot fix the problems as they are encountered.

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