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NAME | SYNOPSIS | DESCRIPTION | SAFE OR ADVISORY OPTIONS | DANGEROUS OPTIONS | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON |
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BTRFS-CHECK(8) Btrfs Manual BTRFS-CHECK(8)
btrfs-check - check or repair a btrfs filesystem
btrfs check [options] <device>
The filesystem checker is used to verify structural integrity of
a filesystem and attempt to repair it if requested. It is
recommended to unmount the filesystem prior to running the check,
but it is possible to start checking a mounted filesystem (see
--force).
By default, btrfs check will not modify the device but you can
reaffirm that by the option --readonly.
btrfsck is an alias of btrfs check command and is now deprecated.
Warning
Do not use --repair unless you are advised to do so by a
developer or an experienced user, and then only after having
accepted that no fsck successfully repair all types of
filesystem corruption. Eg. some other software or hardware
bugs can fatally damage a volume.
The structural integrity check verifies if internal filesystem
objects or data structures satisfy the constraints, point to the
right objects or are correctly connected together.
There are several cross checks that can detect wrong reference
counts of shared extents, backreferences, missing extents of
inodes, directory and inode connectivity etc.
The amount of memory required can be high, depending on the size
of the filesystem, similarly the run time. Check the modes that
can also affect that.
-b|--backup
use the first valid set of backup roots stored in the
superblock
This can be combined with --super if some of the superblocks
are damaged.
--check-data-csum
verify checksums of data blocks
This expects that the filesystem is otherwise OK, and is
basically an offline scrub that does not repair data from
spare copies.
--chunk-root <bytenr>
use the given offset bytenr for the chunk tree root
-E|--subvol-extents <subvolid>
show extent state for the given subvolume
-p|--progress
indicate progress at various checking phases
-Q|--qgroup-report
verify qgroup accounting and compare against filesystem
accounting
-r|--tree-root <bytenr>
use the given offset bytenr for the tree root
--readonly
(default) run in read-only mode, this option exists to calm
potential panic when users are going to run the checker
-s|--super <superblock>
use 'superblock’th superblock copy, valid values are 0, 1 or
2 if the respective superblock offset is within the device
size
This can be used to use a different starting point if some of
the primary superblock is damaged.
--clear-space-cache v1|v2
completely wipe all free space cache of given type
For free space cache v1, the clear_cache kernel mount option
only rebuilds the free space cache for block groups that are
modified while the filesystem is mounted with that option.
Thus, using this option with v1 makes it possible to actually
clear the entire free space cache.
For free space cache v2, the clear_cache kernel mount option
destroys the entire free space cache. This option, with v2
provides an alternative method of clearing the free space
cache that doesn’t require mounting the filesystem.
--clear-ino-cache
remove leftover items pertaining to the deprecated inode map
feature
--repair
enable the repair mode and attempt to fix problems where
possible
Note
there’s a warning and 10 second delay when this option is
run without --force to give users a chance to think twice
before running repair, the warnings in documentation have
shown to be insufficient
--init-csum-tree
create a new checksum tree and recalculate checksums in all
files
Note
Do not blindly use this option to fix checksum mismatch
problems.
--init-extent-tree
build the extent tree from scratch
Note
Do not use unless you know what you’re doing.
--mode <MODE>
select mode of operation regarding memory and IO
The MODE can be one of:
original
The metadata are read into memory and verified, thus the
requirements are high on large filesystems and can even
lead to out-of-memory conditions. The possible workaround
is to export the block device over network to a machine
with enough memory.
lowmem
This mode is supposed to address the high memory
consumption at the cost of increased IO when it needs to
re-read blocks. This may increase run time.
Note
lowmem mode does not work with --repair yet, and is
still considered experimental.
--force
allow work on a mounted filesystem. Note that this should
work fine on a quiescent or read-only mounted filesystem but
may crash if the device is changed externally, eg. by the
kernel module. Repair without mount checks is not supported
right now.
This option also skips the delay and warning in the repair
mode (see --repair).
btrfs check 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
http://btrfs.wiki.kernel.org for further details.
mkfs.btrfs(8), btrfs-scrub(8), btrfs-rescue(8)
This page is part of the btrfs-progs (btrfs filesystem tools)
project. Information about the project can be found at
⟨https://btrfs.wiki.kernel.org/index.php/Btrfs_source_repositories⟩.
If you have a bug report for this manual page, see
⟨https://btrfs.wiki.kernel.org/index.php/Problem_FAQ#How_do_I_report_bugs_and_issues.3F⟩.
This page was obtained from the project's upstream Git repository
⟨git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git⟩
on 2024-06-14. (At that time, the date of the most recent commit
that was found in the repository was 2024-05-02.) If you
discover any rendering problems in this HTML version of the page,
or you believe there is a better or more up-to-date source for
the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original
manual page), send a mail to man-pages@man7.org
Btrfs v5.16.1 02/06/2022 BTRFS-CHECK(8)
Pages that refer to this page: btrfs(8), btrfs-rescue(8), btrfs-restore(8), fsck.btrfs(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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