btrfs-convert(8)

1BTRFS-CONVERT(8)                 Btrfs Manual                 BTRFS-CONVERT(8)
2
3
4

NAME

6       btrfs-convert - convert from ext2/3/4 or reiserfs filesystem to btrfs
7       in-place
8

SYNOPSIS

10       btrfs-convert [options] <device>
11

DESCRIPTION

13       btrfs-convert is used to convert existing source filesystem image to a
14       btrfs filesystem in-place. The original filesystem image is accessible
15       in subvolume named like ext2_saved as file image.
16
17       Supported filesystems:
18
19       ·   ext2, ext3, ext4 — original feature, always built in
20
21       ·   reiserfs — since version 4.13, optionally built, requires
22           libreiserfscore 3.6.27
23
24       The list of supported source filesystem by a given binary is listed at
25       the end of help (option --help).
26
27           Warning
28           If you are going to perform rollback to the original filesystem,
29           you should not execute btrfs balance command on the converted
30           filesystem. This will change the extent layout and make
31           btrfs-convert unable to rollback.
32
33       The conversion utilizes free space of the original filesystem. The
34       exact estimate of the required space cannot be foretold. The final
35       btrfs metadata might occupy several gigabytes on a hundreds-gigabyte
36       filesystem.
37
38       If the ability to rollback is no longer important, the it is
39       recommended to perform a few more steps to transition the btrfs
40       filesystem to a more compact layout. This is because the conversion
41       inherits the original data blocks' fragmentation, and also because the
42       metadata blocks are bound to the original free space layout.
43
44       Due to different constraints, it is only possible to convert
45       filesystems that have a supported data block size (ie. the same that
46       would be valid for mkfs.btrfs). This is typically the system page size
47       (4KiB on x86_64 machines).
48
49           Note
50           The source filesystem should be clean, you are encouraged to run
51           the fsck tool if you’re not sure.
52
53       REMOVE THE ORIGINAL FILESYSTEM METADATA
54
55       By removing the subvolume named like ext2_saved or reiserfs_saved, all
56       metadata of the original filesystem will be removed:
57
58           # btrfs subvolume delete /mnt/ext2_saved
59
60       At this point it is not possible to do a rollback. The filesystem is
61       usable but may be impacted by the fragmentation inherited from the
62       original filesystem.
63
64       MAKE FILE DATA MORE CONTIGUOUS
65
66       An optional but recommended step is to run defragmentation on the
67       entire filesystem. This will attempt to make file extents more
68       contiguous.
69
70           # btrfs filesystem defrag -v -r -f -t 32M /mnt/btrfs
71
72       Verbose recursive defragmentation (-v, -r), flush data per-file (-f)
73       with target extent size 32MiB (-t).
74
75       ATTEMPT TO MAKE BTRFS METADATA MORE COMPACT
76
77       Optional but recommended step.
78
79       The metadata block groups after conversion may be smaller than the
80       default size (256MiB or 1GiB). Running a balance will attempt to merge
81       the block groups. This depends on the free space layout (and
82       fragmentation) and may fail due to lack of enough work space. This is a
83       soft error leaving the filesystem usable but the block group layout may
84       remain unchanged.
85
86       Note that balance operation takes a lot of time, please see also
87       btrfs-balance(8).
88
89           # btrfs balance start -m /mnt/btrfs
90

OPTIONS

92       --csum <type>, --checksum <type>
93           Specify the checksum algorithm. Default is crc32c. Valid values are
94           crc32c, xxhash, sha256 or blake2. To mount such filesystem kernel
95           must support the checksums as well.
96
97       -d|--no-datasum
98           disable data checksum calculations and set the NODATASUM file flag,
99           this can speed up the conversion
100
101       -i|--no-xattr
102           ignore xattrs and ACLs of files
103
104       -n|--no-inline
105           disable inlining of small files to metadata blocks, this will
106           decrease the metadata consumption and may help to convert a
107           filesystem with low free space
108
109       -N|--nodesize <SIZE>
110           set filesystem nodesize, the tree block size in which btrfs stores
111           its metadata. The default value is 16KB (16384) or the page size,
112           whichever is bigger. Must be a multiple of the sectorsize, but not
113           larger than 65536. See mkfs.btrfs(8) for more details.
114
115       -r|--rollback
116           rollback to the original ext2/3/4 filesystem if possible
117
118       -l|--label <LABEL>
119           set filesystem label during conversion
120
121       -L|--copy-label
122           use label from the converted filesystem
123
124       -O|--features <feature1>[,<feature2>...]
125           A list of filesystem features enabled the at time of conversion.
126           Not all features are supported by old kernels. To disable a
127           feature, prefix it with ^. Description of the features is in
128           section FILESYSTEM FEATURES of mkfs.btrfs(8).
129
130           To see all available features that btrfs-convert supports run:
131
132           btrfs-convert -O list-all
133
134       -p|--progress
135           show progress of conversion (a heartbeat indicator and number of
136           inodes processed), on by default
137
138       --no-progress
139           disable progress and show only the main phases of conversion
140

EXIT STATUS

142       btrfs-convert will return 0 if no error happened. If any problems
143       happened, 1 will be returned.
144

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXIT STATUS

SEE ALSO