NAME
----
-btrfs-convert - convert from ext2/3/4 filesystem to btrfs
+btrfs-convert - convert from ext2/3/4 or reiserfs filesystem to btrfs in-place
SYNOPSIS
--------
DESCRIPTION
-----------
-*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'.
+*btrfs-convert* is used to convert existing source filesystem image to a btrfs
+filesystem in-place. The original filesystem image is accessible in subvolume
+named like 'ext2_saved' as file 'image'.
-WARNING: 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 rollback.
+Supported filesystems:
+
+* ext2, ext3, ext4 -- original feature, always built in
+
+* reiserfs -- since version 4.13, optionally built, requires libreiserfscore 3.6.27
+
+The list of supported source filesystem by a given binary is listed at the end
+of help (option '--help').
+
+WARNING: If you are going to perform rollback to the original filesystem, you
+should not execute *btrfs balance* command on the converted filesystem. This
+will change the extent layout and make *btrfs-convert* unable to rollback.
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 filesystem.
-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.
+If the ability to rollback is no longer important, the it is recommended to
+perform a few more steps to transition the btrfs filesystem to a more compact
+layout. This is because the conversion inherits the original data blocks'
+fragmentation, and also because the metadata blocks are bound to the original
+free space layout.
+
+Due to different constraints, it is only possible to convert filesystems that
+have a 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).
+
+NOTE: The source filesystem should be clean, you are encouraged to run the
+'fsck' tool if you're not sure.
**REMOVE THE ORIGINAL FILESYSTEM METADATA**
-By removing the 'ext2_saved' subvolume, all metadata of the original filesystem
-will be removed:
+By removing the subvolume named like 'ext2_saved' or 'reiserfs_saved', 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.
+At this point it is not possible to do a rollback. The filesystem is usable but
+may be impacted by the fragmentation inherited from the original filesystem.
**MAKE FILE DATA MORE CONTIGUOUS**
# btrfs filesystem defrag -v -r -f -t 32M /mnt/btrfs
-Verbose recursive defragmentation ('-v', '-r'), flush data per-file ('-f') with target
-extent size 32M ('-t').
+Verbose recursive defragmentation ('-v', '-r'), flush data per-file ('-f') with
+target extent size 32MiB ('-t').
**ATTEMPT TO MAKE BTRFS METADATA MORE COMPACT**
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. This is
-a soft error leaving the filesystem usable but the block group layout may
-remain unchanged.
+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.
+Note that balance operation takes a lot of time, please see also
+`btrfs-balance`(8).
# btrfs balance start -m /mnt/btrfs
OPTIONS
-------
-d|--no-datasum::
-disable data checksum calculations and set NODATASUM file flag, this can speed
+disable data checksum calculations and set the NODATASUM file flag, this can speed
up the conversion
-i|--no-xattr::
ignore xattrs and ACLs of files
-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. Se
+Must be a multiple of the sectorsize, but not larger than 65536. See
`mkfs.btrfs`(8) for more details.
-r|--rollback::
rollback to the original ext2/3/4 filesystem if possible
-L|--copy-label::
use label from the converted filesystem
-O|--features <feature1>[,<feature2>...]::
-A list of filesystem features turned on at btrfs-convert time. Not all features
+A list of filesystem features enabled the at time of conversion. 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+
++
-p|--progress::
-show progress of conversion, on by default
+show progress of conversion (a heartbeat indicator and number of inodes
+processed), on by default
--no-progress::
-disable detailed progress and show only the main phases of conversion
+disable progress and show only the main phases of conversion
EXIT STATUS
-----------
projects / platform / upstream / btrfs-progs.git / blobdiff