NAME | SYNOPSIS | DESCRIPTION | SUBCOMMAND | EXIT STATUS | AVAILABILITY | SEE ALSO | COLOPHON

BTRFS-RESCUE(8)                 Btrfs Manual                 BTRFS-RESCUE(8)

NAME         top

       btrfs-rescue - Recover a damaged btrfs filesystem

SYNOPSIS         top

       btrfs rescue <subcommand> <args>

DESCRIPTION         top

       btrfs rescue is used to try to recover a damaged btrfs filesystem.

SUBCOMMAND         top

       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.

       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 has been fixed a long time ago, so
       it is unlikely that you will see this particular problem, but the
       utility 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.

EXIT STATUS         top

       btrfs rescue returns a zero exit status if it succeeds. Non zero is
       returned in case of failure.

AVAILABILITY         top

       btrfs is part of btrfs-progs. Please refer to the btrfs wiki
       http://btrfs.wiki.kernel.org for further details.

SEE ALSO         top

       mkfs.btrfs(8), btrfs-scrub(8), btrfs-check(8)

COLOPHON         top

       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 2017-03-13.  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                     07/16/2016                  BTRFS-RESCUE(8)