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| − | =btrfs-check(8) manual page=
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| | {{GeneratedManpage | | {{GeneratedManpage |
| | |name=btrfs-check}} | | |name=btrfs-check}} |
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| − | ==NAME==
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| − | btrfs-check - check or repair a btrfs filesystem
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| − |
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| − | ==SYNOPSIS==
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| − |
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| − | <p><b>btrfs check</b> [options] <em><device></em></p>
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| − | ==DESCRIPTION==
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| − |
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| − | <p>The filesystem checker is used to verify structural integrity of a filesystem
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| − | and attempt to repair it if requested. It is recommended to unmount the
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| − | filesystem prior to running the check, but it is possible to start checking a
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| − | mounted filesystem (see <em>--force</em>).</p>
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| − | <p>By default, <b>btrfs check</b> will not modify the device but you can reaffirm that
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| − | by the option <em>--readonly</em>.</p>
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| − | <p><b>btrfsck</b> is an alias of <b>btrfs check</b> command and is now deprecated.</p>
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| − | <blockquote><b>Warning:</b>
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| − | Do not use <em>--repair</em> unless you are advised to do so by a developer
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| − | or an experienced user, and then only after having accepted that no <em>fsck</em>
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| − | successfully repair all types of filesystem corruption. Eg. some other software
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| − | or hardware bugs can fatally damage a volume.</blockquote>
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| − | <p>The structural integrity check verifies if internal filesystem objects or
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| − | data structures satisfy the constraints, point to the right objects or are
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| − | correctly connected together.</p>
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| − | <p>There are several cross checks that can detect wrong reference counts of shared
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| − | extents, backreferences, missing extents of inodes, directory and inode
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| − | connectivity etc.</p>
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| − | <p>The amount of memory required can be high, depending on the size of the
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| − | filesystem, similarly the run time. Check the modes that can also affect that.</p>
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| − | ==SAFE OR ADVISORY OPTIONS==
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| − |
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| − | <dl>
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| − | <dt>
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| − | -b|--backup
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| − | <dd>
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| − | <p>
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| − | use the first valid set of backup roots stored in the superblock
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| − | </p>
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| − | <p>This can be combined with <em>--super</em> if some of the superblocks are damaged.</p>
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| − |
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| − | <dt>
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| − | --check-data-csum
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| − | <dd>
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| − | <p>
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| − | verify checksums of data blocks
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| − | </p>
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| − | <p>This expects that the filesystem is otherwise OK, and is basically an offline
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| − | <em>scrub</em> that does not repair data from spare copies.</p>
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| − |
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| − | <dt>
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| − | --chunk-root <em><bytenr></em>
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| − | <dd>
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| − | <p>
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| − | use the given offset <em>bytenr</em> for the chunk tree root
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| − | </p>
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| − |
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| − | <dt>
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| − | -E|--subvol-extents <em><subvolid></em>
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| − | <dd>
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| − | <p>
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| − | show extent state for the given subvolume
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| − | </p>
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| − |
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| − | <dt>
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| − | -p|--progress
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| − | <dd>
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| − | <p>
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| − | indicate progress at various checking phases
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| − | </p>
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| − |
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| − | <dt>
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| − | -Q|--qgroup-report
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| − | <dd>
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| − | <p>
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| − | verify qgroup accounting and compare against filesystem accounting
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| − | </p>
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| − |
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| − | <dt>
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| − | -r|--tree-root <em><bytenr></em>
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| − | <dd>
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| − | <p>
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| − | use the given offset <em>bytenr</em> for the tree root
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| − | </p>
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| − |
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| − | <dt>
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| − | --readonly
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| − | <dd>
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| − | <p>
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| − | (default)
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| − | run in read-only mode, this option exists to calm potential panic when users
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| − | are going to run the checker
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| − | </p>
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| − |
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| − | <dt>
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| − | -s|--super <em><superblock></em>
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| − | <dd>
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| − | <p>
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| − | use 'superblock’th superblock copy, valid values are 0, 1 or 2 if the
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| − | respective superblock offset is within the device size
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| − | </p>
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| − | <p>This can be used to use a different starting point if some of the primary
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| − | superblock is damaged.</p>
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| − |
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| − | <dt>
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| − | --clear-space-cache v1|v2
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| − | <dd>
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| − | <p>
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| − | completely wipe all free space cache of given type
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| − | </p>
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| − | <p>For free space cache <em>v1</em>, the <em>clear_cache</em> kernel mount option only rebuilds
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| − | the free space cache for block groups that are modified while the filesystem is
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| − | mounted with that option. Thus, using this option with <em>v1</em> makes it possible
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| − | to actually clear the entire free space cache.</p>
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| − | <p>For free space cache <em>v2</em>, the <em>clear_cache</em> kernel mount option destroys
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| − | the entire free space cache. This option, with <em>v2</em> provides an alternative
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| − | method of clearing the free space cache that doesn’t require mounting the
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| − | filesystem.</p>
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| − |
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| − | <dt>
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| − | --clear-ino-cache
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| − | <dd>
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| − | <p>
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| − | remove leftover items pertaining to the deprecated inode map feature
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| − | </p>
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| − |
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| − | </dl>
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| − | ==DANGEROUS OPTIONS==
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| − |
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| − | <dl>
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| − | <dt>
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| − | --repair
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| − | <dd>
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| − | <p>
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| − | enable the repair mode and attempt to fix problems where possible
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| − | </p>
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| − | <blockquote><b>Note:</b>
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| − | there’s a warning and 10 second delay when this option is run without
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| − | <em>--force</em> to give users a chance to think twice before running repair, the
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| − | warnings in documentation have shown to be insufficient</blockquote>
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| − |
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| − | <dt>
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| − | --init-csum-tree
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| − | <dd>
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| − | <p>
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| − | create a new checksum tree and recalculate checksums in all files
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| − | </p>
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| − | <blockquote><b>Note:</b>
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| − | Do not blindly use this option to fix checksum mismatch problems.</blockquote>
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| − |
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| − | <dt>
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| − | --init-extent-tree
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| − | <dd>
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| − | <p>
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| − | build the extent tree from scratch
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| − | </p>
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| − | <blockquote><b>Note:</b>
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| − | Do not use unless you know what you’re doing.</blockquote>
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| − |
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| − | <dt>
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| − | --mode <em><MODE></em>
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| − | <dd>
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| − | <p>
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| − | select mode of operation regarding memory and IO
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| − | </p>
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| − | <p>The <em>MODE</em> can be one of:</p>
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| − | <dl>
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| − | <dt>
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| − | <em>original</em>
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| − | <dd>
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| − | <p>
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| − | The metadata are read into memory and verified, thus the requirements are high
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| − | on large filesystems and can even lead to out-of-memory conditions. The
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| − | possible workaround is to export the block device over network to a machine
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| − | with enough memory.
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| − | </p>
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| − |
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| − | <dt>
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| − | <em>lowmem</em>
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| − | <dd>
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| − | <p>
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| − | This mode is supposed to address the high memory consumption at the cost of
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| − | increased IO when it needs to re-read blocks. This may increase run time.
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| − | </p>
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| − | <blockquote><b>Note:</b>
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| − | <em>lowmem</em> mode does not work with <em>--repair</em> yet, and is still considered
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| − | experimental.</blockquote>
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| − |
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| − | </dl>
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| − |
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| − | <dt>
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| − | --force
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| − | <dd>
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| − | <p>
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| − | allow work on a mounted filesystem. Note that this should work fine on a
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| − | quiescent or read-only mounted filesystem but may crash if the device is
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| − | changed externally, eg. by the kernel module. Repair without mount checks is
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| − | not supported right now.
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| − | </p>
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| − | <p>This option also skips the delay and warning in the repair mode (see
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| − | <em>--repair</em>).</p>
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| − |
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| − | </dl>
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| − | ==EXIT STATUS==
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| − |
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| − | <p><b>btrfs check</b> returns a zero exit status if it succeeds. Non zero is
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| − | returned in case of failure.</p>
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| − | ==AVAILABILITY==
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| − |
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| − | <p><b>btrfs</b> 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.</p>
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| − | ==SEE ALSO==
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| − |
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| − | <p>[[Manpage/mkfs.btrfs|mkfs.btrfs(8)]],
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| − | [[Manpage/btrfs-scrub|btrfs-scrub(8)]],
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| − | [[Manpage/btrfs-rescue|btrfs-rescue(8)]]</p>
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| − | [[Category:Manpage]]
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