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NAME
       xfs_repair - repair an XFS filesystem

SYNOPSIS
       xfs_repair  [  -dfLnPv  ]  [  -m maxmem ] [ -c subopt=value ] [ -o sub-
       opt[=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.

       -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.

       -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:

                 ihash=ihashsize
                        overrides the default inode cache hash size. The total
                        number  of  inode cache entries are limited to 8 times
                        this amount. The default  ihashsize  is  1024  (for  a
                        total of 8192 entries).

                 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  and
                        exist  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. During long runs  xfs_repair  outputs
              its  progress every 15 minutes. Reporting is only activated when
              ag_stride is enabled.

       -v     Verbose output.

       -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.

       -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 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 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_check(8),  xfs_metad-
       ump(8), xfs(5).

                                                                 xfs_repair(8)

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