NAME

       xfs_scrub - check and repair the contents of a mounted XFS filesystem

SYNOPSIS

       xfs_scrub [ -abCemnTvx ] mount-point
       xfs_scrub -V

DESCRIPTION

       xfs_scrub attempts to check and repair all metadata in a mounted XFS filesystem.

       WARNING!   This  program is EXPERIMENTAL, which means that its behavior and interface could change at any
       time!

       xfs_scrub asks the kernel to scrub all metadata objects in the filesystem.  Metadata records are  scanned
       for  obviously  bad  values and then cross-referenced against other metadata.  The goal is to establish a
       reasonable confidence about the consistency of the overall filesystem by  examining  the  consistency  of
       individual  metadata  records  against  the  other  metadata  in the filesystem.  Damaged metadata can be
       rebuilt from other metadata if there exists redundant data structures which are intact.

       Filesystem corruption and optimization opportunities  will  be  logged  to  the  standard  error  stream.
       Enabling verbose mode will increase the amount of status information sent to the output.

       If the kernel scrub reports that metadata needs repairs or optimizations and the user does not pass -n on
       the command line, this program will ask the kernel to make the repairs and to perform the  optimizations.
       See  the  sections  about optimizations and repairs for a list of optimizations and repairs known to this
       program.  The kernel may not support repairing or optimizing the filesystem.  If this is  the  case,  the
       filesystem must be unmounted and xfs_repair(8) run on the filesystem to fix the problems.

OPTIONS

       -a errors
              Abort if more than this many errors are found on the filesystem.

       -b     Run  in background mode.  If the option is specified once, only run a single scrubbing thread at a
              time.  If given more than once, an artificial delay of 100us is added to each scrub call to reduce
              CPU overhead even further.

       -C fd  This  option  causes  xfs_scrub to write progress information to the specified file description so
              that the progress of the filesystem check can be monitored.  If the file description is a  tty,  a
              fancy  progress bar is rendered.  Otherwise, a simple numeric status dump compatible with the fsck
              -C format is output.

       -e     Specifies what happens when errors are detected.  If shutdown is given,  the  filesystem  will  be
              taken  offline if errors are found.  If continue is given, no action is taken if errors are found;
              this is the default behavior.

       -k     Do not call TRIM on the free space.

       -m file
              Search this file for mounted filesystems instead of /etc/mtab.

       -n     Only check filesystem metadata.  Do not repair or optimize anything.

       -T     Print timing and memory usage information for each phase.

       -v     Enable verbose mode, which prints periodic status updates.

       -V     Prints the version number and exits.

       -x     Read all file data extents to look for disk errors.  xfs_scrub will issue O_DIRECT  reads  to  the
              block  device  directly.   If  the  block device is a SCSI disk, it will instead issue READ VERIFY
              commands directly to the disk.  If media errors are found, the error report will include the  disk
              offset,  in  bytes.   If  the  media  errors affect a file, the report will also include the inode
              number and file offset, in bytes.  These actions will confirm that all file  data  blocks  can  be
              read from storage.

OPTIMIZATIONS

       Optimizations supported by this program include, but are not limited to:

       • Instructing the underlying storage to discard unused extents via the TRIM ioctl.

       • Updating secondary superblocks to match the primary superblock.

       • Turning off shared block write checks for files that no longer share blocks.

REPAIRS

       Repairs  are  performed  by  calling  into  the  kernel.   This  limits the scope of repair activities to
       rebuilding primary data structures from secondary data structures, or secondary structures  from  primary
       structures.   The  existence of secondary data structures may require features that can only be turned on
       from mkfs.xfs(8).  If errors cannot be repaired, the filesystem must be unmounted and xfs_repair(8)  run.
       Repairs supported by the kernel include, but are not limited to:

       • Reconstructing extent allocation data.

       • Rebuilding free space information.

       • Rebuilding inode indexes.

       • Fixing minor corruptions of inode records.

       • Recalculating reference count information.

       • Reconstructing reverse mapping data from primary extent allocation data.

       • Scheduling a quotacheck for the next mount.

       If  corrupt  metadata is successfully repaired, this program will log that a repair has succeeded instead
       of a corruption report.

EXIT CODE

       The exit code returned by xfs_scrub is the sum of the following conditions:
            0    - No errors
            1    - File system errors left uncorrected
            2    - File system optimizations possible
            4    - Operational error
            8    - Usage or syntax error

CAVEATS

       xfs_scrub is an immature utility!  Do not run this program unless you have backups of  your  data!   This
       program  takes  advantage of in-kernel scrubbing to verify a given data structure with locks held and can
       keep the filesystem busy for a long time.  The kernel must be new enough to  support  the  SCRUB_METADATA
       ioctl.

       If errors are found and cannot be repaired, the filesystem must be unmounted and repaired.

SEE ALSO

       xfs_repair(8).

                                                                                                    xfs_scrub(8)