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

NAME
       btrfs-scrub - scrub btrfs filesystem, verify block checksums
SYNOPSIS
       btrfs scrub <subcommand> <args>
DESCRIPTION
       btrfs scrub is used to scrub a 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.
       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 interfere with normal filesystem operation
       significantly.
       The scrubbing status is recorded in /var/lib/btrfs/ in textual files
       named scrub.status.UUID for a filesystem identified by the given UUID.
       (An itermediate progress is communicated through a named pipe in file
       scrub.progress.UUID in the same directory.) The status file is updated
       periodically every 5 seconds. An resumed scrub will continue from the
       last saved position.
SUBCOMMAND
       cancel <path>|<device>
           If a scrub is running on the filesystem identified by path 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.
       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.
           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 filesystem identified by path
           or on a single device. If a scrub is already running, the new one
           fails.
           Without options, scrub is started as a background process.
           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.
           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
           -q
               be quiet, omit error messages and statistics
           -r
               run in read-only mode, do not attempt to correct anything, can
               be run on a read-only filesystem
           -R
               print raw statistics per-device instead of a 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
       status [-d] <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
EXIT STATUS
       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
       btrfs is part of btrfs-progs. Please refer to the btrfs wiki
       http://btrfs.wiki.kernel.org for further details.
SEE ALSO
       mkfs.btrfs(8), ionice(1)

Btrfs v4.9.1                      08/06/2017                    BTRFS-SCRUB(8)