btrfs-scrub(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | SUBCOMMAND | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON

BTRFS-SCRUB(8)                Btrfs Manual                BTRFS-SCRUB(8)

NAME         top

       btrfs-scrub - scrub btrfs filesystem, verify block checksums

SYNOPSIS         top

       btrfs scrub <subcommand> <args>

DESCRIPTION         top

       btrfs scrub is used to scrub a mounted btrfs filesystem, which
       will read all data and metadata blocks from all devices and
       verify checksums. Automatically repair corrupted blocks if
       there’s a correct copy available.

           Note
           Scrub is not a filesystem checker (fsck) and does not verify
           nor repair structural damage in the filesystem. It really
           only checks checksums of data and tree blocks, it doesn’t
           ensure the content of tree blocks is valid and consistent.
           There’s some validation performed when metadata blocks are
           read from disk but it’s not extensive and cannot substitute
           full btrfs check run.

       The user is supposed to run it manually or via a periodic system
       service. The recommended period is a month but could be less. The
       estimated device bandwidth utilization is about 80% on an idle
       filesystem. The IO priority class is by default idle so
       background scrub should not significantly interfere with normal
       filesystem operation. The IO scheduler set for the device(s)
       might not support the priority classes though.

       The scrubbing status is recorded in /var/lib/btrfs/ in textual
       files named scrub.status.UUID for a filesystem identified by the
       given UUID. (Progress state is communicated through a named pipe
       in file scrub.progress.UUID in the same directory.) The status
       file is updated every 5 seconds. A resumed scrub will continue
       from the last saved position.

       Scrub can be started only on a mounted filesystem, though it’s
       possible to scrub only a selected device. See scrub start for
       more.

SUBCOMMAND         top

       cancel <path>|<device>
           If a scrub is running on the filesystem identified by path or
           device, cancel it.

           If a device is specified, the corresponding filesystem is
           found and btrfs scrub cancel behaves as if it was called on
           that filesystem. The progress is saved in the status file so
           btrfs scrub resume can continue from the last position.

       resume [-BdqrR] [-c <ioprio_class> -n <ioprio_classdata>]
       <path>|<device>
           Resume a cancelled or interrupted scrub on the filesystem
           identified by path or on a given device. The starting point
           is read from the status file if it exists.

           This does not start a new scrub if the last scrub finished
           successfully.

           Options

           see scrub start.

       start [-BdqrRf] [-c <ioprio_class> -n <ioprio_classdata>]
       <path>|<device>
           Start a scrub on all devices of the mounted filesystem
           identified by path or on a single device. If a scrub is
           already running, the new one will not start. A device of an
           unmounted filesystem cannot be scrubbed this way.

           Without options, scrub is started as a background process.
           The automatic repairs of damaged copies is performed by
           default for block group profiles with redundancy.

           The default IO priority of scrub is the idle class. The
           priority can be configured similar to the ionice(1) syntax
           using -c and -n options. Note that not all IO schedulers
           honor the ionice settings.

           Options

           -B
               do not background and print scrub statistics when
               finished

           -d
               print separate statistics for each device of the
               filesystem (-B only) at the end

           -r
               run in read-only mode, do not attempt to correct
               anything, can be run on a read-only filesystem

           -R
               raw print mode, print full data instead of summary

           -c <ioprio_class>
               set IO priority class (see ionice(1) manpage)

           -n <ioprio_classdata>
               set IO priority classdata (see ionice(1) manpage)

           -f
               force starting new scrub even if a scrub is already
               running, this can useful when scrub status file is
               damaged and reports a running scrub although it is not,
               but should not normally be necessary

           -q
               (deprecated) alias for global -q option

       status [options] <path>|<device>
           Show status of a running scrub for the filesystem identified
           by path or for the specified device.

           If no scrub is running, show statistics of the last finished
           or cancelled scrub for that filesystem or device.

           Options

           -d
               print separate statistics for each device of the
               filesystem

           -R
               print all raw statistics without postprocessing as
               returned by the status ioctl

           --raw
               print all numbers raw values in bytes without the B
               suffix

           --human-readable
               print human friendly numbers, base 1024, this is the
               default

           --iec
               select the 1024 base for the following options, according
               to the IEC standard

           --si
               select the 1000 base for the following options, according
               to the SI standard

           --kbytes
               show sizes in KiB, or kB with --si

           --mbytes
               show sizes in MiB, or MB with --si

           --gbytes
               show sizes in GiB, or GB with --si

           --tbytes
               show sizes in TiB, or TB with --si

EXIT STATUS         top

       btrfs scrub returns a zero exit status if it succeeds. Non zero
       is returned in case of failure:

       1
           scrub couldn’t be performed

       2
           there is nothing to resume

       3
           scrub found uncorrectable errors

AVAILABILITY         top

       btrfs is part of btrfs-progs. Please refer to the btrfs wiki
       http://btrfs.wiki.kernel.org for further details.

SEE ALSO         top

       mkfs.btrfs(8), ionice(1)

COLOPHON         top

       This page is part of the btrfs-progs (btrfs filesystem tools)
       project.  Information about the project can be found at 
       ⟨https://btrfs.wiki.kernel.org/index.php/Btrfs_source_repositories⟩.
       If you have a bug report for this manual page, see
       ⟨https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#How_do_I_report_bugs_and_issues.3F⟩.
       This page was obtained from the project's upstream Git repository
       ⟨git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git⟩
       on 2021-08-27.  (At that time, the date of the most recent commit
       that was found in the repository was 2021-07-30.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to man-pages@man7.org

Btrfs v4.6.1                   03/13/2021                 BTRFS-SCRUB(8)

Pages that refer to this page: btrfs(8)btrfs-check(8)btrfs-rescue(8)