mirror of
https://github.com/kdave/btrfs-progs
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167 lines
5.6 KiB
ReStructuredText
167 lines
5.6 KiB
ReStructuredText
btrfs-check(8)
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==============
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SYNOPSIS
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--------
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**btrfs check** [options] <device>
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DESCRIPTION
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-----------
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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 *--force*).
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By default, **btrfs check** will not modify the device but you can reaffirm that
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by the option *--readonly*.
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**btrfsck** is an alias of **btrfs check** command and is now deprecated.
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.. warning::
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Do not use *--repair* 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 *fsck*
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successfully repair all types of filesystem corruption. E.g. some other software
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or hardware bugs can fatally damage a volume.
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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.
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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.
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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.
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SAFE OR ADVISORY OPTIONS
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------------------------
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-b|--backup
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use the first valid set of backup roots stored in the superblock
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This can be combined with *--super* if some of the superblocks are damaged.
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--check-data-csum
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verify checksums of data blocks
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This expects that the filesystem is otherwise OK, and is basically an offline
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*scrub* that does not repair data from spare copies.
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--chunk-root <bytenr>
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use the given offset *bytenr* for the chunk tree root
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-E|--subvol-extents <subvolid>
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show extent state for the given subvolume
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-p|--progress
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indicate progress at various checking phases
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-Q|--qgroup-report
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verify qgroup accounting and compare against filesystem accounting
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-r|--tree-root <bytenr>
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use the given offset 'bytenr' for the tree root
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--readonly
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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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-s|--super <N>
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use Nth 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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This can be used to use a different starting point if some of the primary
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superblock is damaged.
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--clear-space-cache v1|v2
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completely wipe all free space cache of given type
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For free space cache *v1*, the *clear_cache* 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 *v1* makes it possible
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to actually clear the entire free space cache.
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For free space cache *v2*, the *clear_cache* kernel mount option destroys
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the entire free space cache. This option, with *v2* 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.
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--clear-ino-cache
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remove leftover items pertaining to the deprecated inode map feature
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DANGEROUS OPTIONS
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-----------------
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--repair
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enable the repair mode and attempt to fix problems where possible
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.. note::
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There's a warning and 10 second delay when this option is run without
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*--force* to give users a chance to think twice before running repair, the
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warnings in documentation have shown to be insufficient
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--init-csum-tree
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create a new checksum tree and recalculate checksums in all files
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.. warning::
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Do not blindly use this option to fix checksum mismatch problems.
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--init-extent-tree
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build the extent tree from scratch
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.. warning::
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Do not use unless you know what you're doing.
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--mode <MODE>
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select mode of operation regarding memory and IO
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The *MODE* can be one of:
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original
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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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lowmem
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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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.. note::
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*lowmem* mode does not work with *--repair* yet, and is still considered
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experimental.
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--force
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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, e.g. by the kernel module. Repair without mount checks is
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not supported right now.
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This option also skips the delay and warning in the repair mode (see
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*--repair*).
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EXIT STATUS
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-----------
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**btrfs check** returns a zero exit status if it succeeds. Non zero is
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returned in case of failure.
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AVAILABILITY
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------------
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**btrfs** is part of btrfs-progs. Please refer to the documentation at
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https://btrfs.readthedocs.io or wiki http://btrfs.wiki.kernel.org for further
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information.
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SEE ALSO
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--------
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:doc:`mkfs.btrfs(8)<mkfs.btrfs>`,
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:doc:`btrfs-scrub(8)<btrfs-scrub>`,
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:doc:`btrfs-rescue(8)<btrfs-rescue>`
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