BTRFS-CONVERT(8)                Btrfs Manual                BTRFS-CONVERT(8)

NAME         top

       btrfs-convert - convert from ext2/3/4 filesystem to btrfs in-place

SYNOPSIS         top

       btrfs-convert [options] <device>

DESCRIPTION         top

       btrfs-convert is used to convert existing ext2/3/4 filesystem image
       to a btrfs filesystem in-place. The original filesystem image is
       accessible subvolume named ext2_saved as file image.

           If you are going to perform rollback to ext2/3/4, you should not
           execute btrfs balance command on the converted filesystem. This
           will change the extent layout and make btrfs-convert unable to

       The conversion utilizes free space of the original filesystem. The
       exact estimate of the required space cannot be foretold. The final
       btrfs metadata might occupy several gigabytes on a hundreds-gigabyte

       If you decide not to rollback anymore, it is recommended to perform a
       few more steps to transform the btrfs filesystem to a more compact
       layout. The conversion inherits the original data block fragmentation
       and the metadata blocks are bound to the original free space layout.

       Due to different constraints, it’s possible to convert only
       filesystem that have supported data block size (ie. the same that
       would be valid for mkfs.btrfs). This is typically the system page
       size (4KiB on x86_64 machines).

           The source filesystem should be clean, you are encouraged to run
           the fsck tool if you’re not sure.


       By removing the ext2_saved subvolume, all metadata of the original
       filesystem will be removed:

           # btrfs subvolume delete /mnt/ext2_saved

       At this point it’s not possible to do rollback. The filesystem is
       usable but may be impacted by the fragmentation inherited from the
       original filesystem.


       An optional but recommended step is to run defragmentation on the
       entire filesystem. This will attempt to make file extents more

           # btrfs filesystem defrag -v -r -f -t 32M /mnt/btrfs

       Verbose recursive defragmentation (-v, -r), flush data per-file (-f)
       with target extent size 32MiB (-t).


       Optional but recommended step.

       The metadata block groups after conversion may be smaller than the
       default size (256MiB or 1GiB). Running a balance will attempt to
       merge the block groups. This depends on the free space layout (and
       fragmentation) and may fail due to lack of enough work space. This is
       a soft error leaving the filesystem usable but the block group layout
       may remain unchanged.

       Note that balance operation takes a lot of time, please see also

           # btrfs balance start -m /mnt/btrfs

OPTIONS         top

           disable data checksum calculations and set the NODATASUM file
           flag, this can speed up the conversion

           ignore xattrs and ACLs of files

           disable inlining of small files to metadata blocks, this will
           decrease the metadata consumption and may help to convert a
           filesystem with low free space

       -N|--nodesize <SIZE>
           set filesystem nodesize, the tree block size in which btrfs
           stores its metadata. The default value is 16KB (16384) or the
           page size, whichever is bigger. Must be a multiple of the
           sectorsize, but not larger than 65536. See mkfs.btrfs(8) for more

           rollback to the original ext2/3/4 filesystem if possible

       -l|--label <LABEL>
           set filesystem label during conversion

           use label from the converted filesystem

       -O|--features <feature1>[,<feature2>...]
           A list of filesystem features turned on at conversion time. Not
           all features are supported by old kernels. To disable a feature,
           prefix it with ^. Description of the features is in section
           FILESYSTEM FEATURES of mkfs.btrfs(8).

           To see all available features that btrfs-convert supports run:

           btrfs-convert -O list-all

           show progress of conversion (a heartbeat indicator and number of
           inodes processed), on by default

           disable progress and show only the main phases of conversion

EXIT STATUS         top

       btrfs-convert will return 0 if no error happened. If any problems
       happened, 1 will be returned.

SEE ALSO         top


COLOPHON         top

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Btrfs v4.6.1                     12/10/2016                 BTRFS-CONVERT(8)