btrfs-rescue(8) — Linux manual page


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

SUBCOMMAND         top

       chunk-recover [options] <device>
           Recover the chunk tree by scanning the devices


               assume an answer of yes to all questions.


               (deprecated) alias for global -v option


           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]

       clear-uuid-tree <device>
           Clear uuid tree, so that kernel can re-generate it at next
           read-write mount.

           Since kernel v4.16 there and more sanity check performed, and
           sometimes non-critical trees like uuid tree can cause
           problems and reject the mount. In such case, clearing uuid
           tree may make the filesystem to be mountable again without
           much risk as it’s built from other trees.

       super-recover [options] <device>
           Recover bad superblocks from good copies.


               assume an answer of yes to all questions.

               (deprecated) alias for global -v option

       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.

               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 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 
       If you have a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       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
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Btrfs v5.16.1                  02/06/2022                BTRFS-RESCUE(8)

Pages that refer to this page: btrfs(8)btrfs-check(8)btrfs-restore(8)