mirror of
https://github.com/kdave/btrfs-progs
synced 2025-02-17 18:26:55 +00:00
42404a4e44
The option "--clear-ino-cache" is not really that suitable for "btrfs check" group. Let's move it to "btrfs rescue" group to fix those small hiccups, just like the existing "btrfs rescue fix-device-size" command. For now, "btrfs check --clear-ino-cache" would still work, with one extra warning referring to "btrfs rescue clear-ino-cache". This is mostly to reduce the surprise, and keep script users (I doubt if there is any though) happy for now. In the next or two releases, we would fully remove the support in "btrfs check" group. Another small change is, in the documents, we refer to the feature as "inode map", which doesn't match with the mount option documents. Since we're here, unify them to "inode cache" feature. Issue: #669 Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
168 lines
5.4 KiB
ReStructuredText
168 lines
5.4 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 :ref:`--force<man-check-option-force>`).
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By default, :command:`btrfs check` will not modify the device but you can reaffirm that
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by the option *--readonly*.
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:command:`btrfsck` is an alias of :command:`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 remove the free space cache of the given version
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See also the *clear_cache* mount option.
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--clear-ino-cache
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remove leftover items pertaining to the deprecated `inode cache` feature
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.. warning::
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This option is deprecated, please use `btrfs rescue clear-ino-cache`
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instead, this option would be removed in the future eventually.
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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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.. _man-check-option-force:
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--force
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allow work on a mounted filesystem and skip mount checks. Note that
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this should work fine on a quiescent or read-only mounted filesystem
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but may crash if the device is changed externally, e.g. by the kernel
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module.
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.. note::
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It is possible to run with --repair but on a mounted filesystem
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that will most likely lead to a corruption unless the filesystem
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is in a quiescent state which may not be possible to guarantee.
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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 <https://btrfs.readthedocs.io>`_.
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SEE ALSO
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--------
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:doc:`mkfs.btrfs`,
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:doc:`btrfs-scrub`,
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:doc:`btrfs-rescue`
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