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

Provided by: xfsprogs_6.13.0-2ubuntu1_amd64

NAME

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

SYNOPSIS

       xfs_scrub [ -abCeMmnpTvx ] 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 real-mount-point
Open the this path for issuing scrub system calls to the kernel. The positional mount-point
parameter will be used for displaying informational messages and logging. This parameter exists
to enable process sandboxing for service mode.

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

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

-o subopt[=value] Override what the program might conclude about the filesystem if left to its own
devices.

The suboptions supported are:

autofsck
Decide the operating mode from the value of the autofsck filesystem property. See the
filesystem properties section for more details.

fstrim_pct=percentage
To constrain the amount of time spent on fstrim activities during phase 8, this program
tries to balance estimated runtime against completeness of the trim. In short, the
program avoids small trim requests to save time.

During phase 7, a log-scale histogram of free space extents is constructed. At the
start of phase 8, a CDF is computed in decreasing order of extent length from the
histogram buckets. A point corresponding to the fstrim percentage target is chosen from
the CDF and mapped back to a histogram bucket. Free space extents at least as long as
the bucket size are trimmed. Smaller extents are ignored.

By default, the percentage threshold is 99%.

iwarn Treat informational messages as warnings. This will result in a nonzero return code,
and a higher logging level.

-p Only optimize filesystem metadata. If repairs are required, report them and exit.

-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.

FILESYSTEM PROPERTIES

       System administrators can convey their preferences for scrubbing of a particular  filesystem  by  setting
       the  filesystem  property  autofsck via the xfs_property(8) command on the filesystem.  These preferences
       will be honored if the -o autofsck option is specified.

       Recognized values for the autofsck property are:

              none   Do not scan the filesystem at all.

              check  Scan and report corruption and opportunities for optimization, but do not change anything.

              optimize
                     Scan the filesystem and optimize where possible.  Report corruptions, but do not fix them.

              repair Scan the filesystem, fix corruptions, and optimize where possible.

       If the property is not set, the default is check if the filesystem has either reverse mapping  btrees  or
       parent pointers enabled, or none otherwise.

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.