btrfs-scrub - scrub btrfs filesystem, verify block checksums


   btrfs scrub <subcommand> <args>


   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

       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
   filesytem. 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.


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

       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>]
       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.


       see scrub start.

   start [-BdqrRf] [-c <ioprio_class> -n <ioprio_classdata>]
       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

       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


           do not background and print scrub statistics when finished

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

           be quiet, omit error messages and statistics

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

           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)

           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

   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.


           print separate statistics for each device of the filesystem


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


   btrfs is part of btrfs-progs. Please refer to the btrfs wiki for further details.


   mkfs.btrfs(8), ionice(1)

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