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NAME | SYNOPSIS | DESCRIPTION | SUBCOMMAND | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON |
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BTRFS-RESCUE(8) Btrfs Manual BTRFS-RESCUE(8)
btrfs-rescue - Recover a damaged btrfs filesystem
btrfs rescue <subcommand> <args>
btrfs rescue is used to try to recover a damaged btrfs filesystem.
chunk-recover [options] <device>
Recover the chunk tree by scanning the devices
Options
-y
assume an answer of yes to all questions.
-v
verbose mode.
-h
help.
Note
Since chunk-recover will scan the whole device, it will be VERY
slow especially executed on a large device.
fix-device-size <device>
fix device size and super block total bytes values that are do
not match
Kernel 4.11 starts to check the device size more strictly and
this might mismatch the stored value of total bytes. See the
exact error message below. Newer kernel will refuse to mount the
filesystem where the values do not match. This error is not fatal
and can be fixed. This command will fix the device size values if
possible.
BTRFS error (device sdb): super_total_bytes 92017859088384 mismatch with fs_devices total_rw_bytes 92017859094528
The mismatch may also exhibit as a kernel warning:
WARNING: CPU: 3 PID: 439 at fs/btrfs/ctree.h:1559 btrfs_update_device+0x1c5/0x1d0 [btrfs]
super-recover [options] <device>
Recover bad superblocks from good copies.
Options
-y
assume an answer of yes to all questions.
-v
verbose mode.
zero-log <device>
clear the filesystem log tree
This command will clear the filesystem log tree. This may fix a
specific set of problem when the filesystem mount fails due to
the log replay. See below for sample stacktraces that may show up
in system log.
The common case where this happens was fixed a long time ago, so
it is unlikely that you will see this particular problem, but the
command is kept around.
Note
clearing the log may lead to loss of changes that were made
since the last transaction commit. This may be up to 30
seconds (default commit period) or less if the commit was
implied by other filesystem activity.
One can determine whether zero-log is needed according to the
kernel backtrace:
? replay_one_dir_item+0xb5/0xb5 [btrfs]
? walk_log_tree+0x9c/0x19d [btrfs]
? btrfs_read_fs_root_no_radix+0x169/0x1a1 [btrfs]
? btrfs_recover_log_trees+0x195/0x29c [btrfs]
? replay_one_dir_item+0xb5/0xb5 [btrfs]
? btree_read_extent_buffer_pages+0x76/0xbc [btrfs]
? open_ctree+0xff6/0x132c [btrfs]
If the errors are like above, then zero-log should be used to
clear the log and the filesystem may be mounted normally again.
The keywords to look for are open_ctree which says that it’s
during mount and function names that contain replay, recover or
log_tree.
btrfs rescue 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-check(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 2018-02-02. (At that time, the date of the most recent commit
that was found in the repository was 2018-01-05.) 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 v4.6.1 01/23/2018 BTRFS-RESCUE(8)
Pages that refer to this page: btrfs(8), btrfs-check(8), btrfs-restore(8)
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