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NAME

       xfs_repair - repair an XFS filesystem

SYNOPSIS

       xfs_repair  [  -dfLnPv  ]  [  -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
       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.

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
              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 rtdev
              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.

       -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
              internal  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
              information 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 fileystem
              from single user mode, immediately followed by a reboot.

       -V     Prints out the current 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)
              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  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. Existing files in a valid  lost+found  are  not  removed  or
       renamed.

   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 ino, moving to lost+found

              An inode numbered  ino  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 (ino).  If  a
              lost+found   directory  does  not  exist,  it  is  automatically
              created.

       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
              references 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
              supplies  the  start,  end,  and file offset of the extent.  The
              message 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
              preceded 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
              message 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
       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.

       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_metadump(8), xfs(5).

                                                                 xfs_repair(8)