119 lines
3.8 KiB
Plaintext
119 lines
3.8 KiB
Plaintext
btrfs-scrub(8)
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==============
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NAME
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----
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btrfs-scrub - scrub btrfs filesystem, verify block checksums
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SYNOPSIS
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--------
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*btrfs scrub* <subcommand> <args>
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DESCRIPTION
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-----------
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*btrfs scrub* is used to scrub a btrfs filesystem, which will read all data
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and metadata blocks from all devices and verify checksums. Automatically repair
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corrupted blocks if there's a correct copy available.
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NOTE: Scrub is not a filesystem checker (fsck) and does not verify nor repair
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structural damage in the filesystem. It really only checks checksums of of data
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and tree blocks, it doesn't ensure the content of tree blocks is valid and
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consistent. There's some validation performed when metadata blocks are read
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from disk but it's not extensive and cannot substitute full 'btrfs check' run.
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The user is supposed to run it manually or via a periodic system service. The
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recommended period is a month but could be less. The estimated device bandwidth
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utilization is about 80% on an idle filesystem. The IO priority class is by
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default 'idle' so background scrub should not significantly interfere with
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normal filesystem operation.
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The scrubbing status is recorded in '/var/lib/btrfs/' in textual files named
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'scrub.status.UUID' for a filesystem identified by the given UUID. (Progress
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state is communicated through a named pipe in file 'scrub.progress.UUID' in the
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same directory.) The status file is updated every 5 seconds. A resumed scrub
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will continue from the last saved position.
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SUBCOMMAND
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----------
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*cancel* <path>|<device>::
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If a scrub is running on the filesystem identified by 'path' cancel it.
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+
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If a 'device' is specified, the corresponding filesystem is found and
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*btrfs scrub cancel* behaves as if it was called on that filesystem.
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*resume* [-BdqrR] [-c <ioprio_class> -n <ioprio_classdata>] <path>|<device>::
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Resume a cancelled or interrupted scrub on the filesystem identified by
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'path' or on a given 'device'.
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+
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Does not start a new scrub if the last scrub finished successfully.
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`Options`
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see *scrub start*.
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*start* [-BdqrRf] [-c <ioprio_class> -n <ioprio_classdata>] <path>|<device>::
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Start a scrub on all devices of the filesystem identified by 'path' or on
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a single 'device'. If a scrub is already running, the new one fails.
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Without options, scrub is started as a background process.
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The default IO priority of scrub is the idle class. The priority can be
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configured similar to the `ionice`(1) syntax using '-c' and '-n' options.
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+
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`Options`
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-B::::
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do not background and print scrub statistics when finished
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-d::::
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print separate statistics for each device of the filesystem ('-B' only) at the end
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-q::::
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be quiet, omit error messages and statistics
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-r::::
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run in read-only mode, do not attempt to correct anything, can be run on a read-only
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filesystem
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-R::::
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raw print mode, print full data instead of summary
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-c <ioprio_class>::::
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set IO priority class (see `ionice`(1) manpage)
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-n <ioprio_classdata>::::
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set IO priority classdata (see `ionice`(1) manpage)
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-f::::
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force starting new scrub even if a scrub is already running,
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this can useful when scrub status file is damaged and reports a running
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scrub although it is not, but should not normally be necessary
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*status* [-d] <path>|<device>::
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Show status of a running scrub for the filesystem identified by 'path' or
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for the specified 'device'.
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+
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If no scrub is running, show statistics of the last finished or cancelled scrub
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for that filesystem or device.
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`Options`
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-d::::
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print separate statistics for each device of the filesystem
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EXIT STATUS
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-----------
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*btrfs scrub* returns a zero exit status if it succeeds. Non zero is
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returned in case of failure:
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1::::
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scrub couldn't be performed
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2::::
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there is nothing to resume
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3::::
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scrub found uncorrectable errors
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AVAILABILITY
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------------
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*btrfs* is part of btrfs-progs.
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Please refer to the btrfs wiki http://btrfs.wiki.kernel.org for
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further details.
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SEE ALSO
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--------
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`mkfs.btrfs`(8),
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`ionice`(1)
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