btrfs-convert(8)

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

NAME

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

SYNOPSIS

9       btrfs-convert [options] <device>
10

DESCRIPTION

12       btrfs-convert is used to convert existing ext2/3/4 filesystem image to
13       a btrfs filesystem in-place. The original filesystem image is
14       accessible subvolume named ext2_saved as file image.
15
16           Warning
17           If you are going to perform rollback to ext2/3/4, you should not
18           execute btrfs balance command on the converted filesystem. This
19           will change the extent layout and make btrfs-convert unable to
20           rollback.
21
22       The conversion utilizes free space of the original filesystem. The
23       exact estimate of the required space cannot be foretold. The final
24       btrfs metadata might occupy several gigabytes on a hundreds-gigabyte
25       filesystem.
26
27       If you decide not to rollback anymore, it is recommended to perform a
28       few more steps to transform the btrfs filesystem to a more compact
29       layout. The conversion inherits the original data block fragmentation
30       and the metadata blocks are bound to the original free space layout.
31
32       Due to different constraints, it’s possible to convert only filesystem
33       that have supported data block size (ie. the same that would be valid
34       for mkfs.btrfs). This is typically the system page size (4KiB on x86_64
35       machines).
36
37           Note
38           The source filesystem should be clean, you are encouraged to run
39           the fsck tool if you’re not sure.
40
41       REMOVE THE ORIGINAL FILESYSTEM METADATA
42
43       By removing the ext2_saved subvolume, all metadata of the original
44       filesystem will be removed:
45
46           # btrfs subvolume delete /mnt/ext2_saved
47
48       At this point it’s not possible to do rollback. The filesystem is
49       usable but may be impacted by the fragmentation inherited from the
50       original filesystem.
51
52       MAKE FILE DATA MORE CONTIGUOUS
53
54       An optional but recommended step is to run defragmentation on the
55       entire filesystem. This will attempt to make file extents more
56       contiguous.
57
58           # btrfs filesystem defrag -v -r -f -t 32M /mnt/btrfs
59
60       Verbose recursive defragmentation (-v, -r), flush data per-file (-f)
61       with target extent size 32MiB (-t).
62
63       ATTEMPT TO MAKE BTRFS METADATA MORE COMPACT
64
65       Optional but recommended step.
66
67       The metadata block groups after conversion may be smaller than the
68       default size (256MiB or 1GiB). Running a balance will attempt to merge
69       the block groups. This depends on the free space layout (and
70       fragmentation) and may fail due to lack of enough work space. This is a
71       soft error leaving the filesystem usable but the block group layout may
72       remain unchanged.
73
74       Note that balance operation takes a lot of time, please see also
75       btrfs-balance(8).
76
77           # btrfs balance start -m /mnt/btrfs
78

OPTIONS

80       -d|--no-datasum
81           disable data checksum calculations and set the NODATASUM file flag,
82           this can speed up the conversion
83
84       -i|--no-xattr
85           ignore xattrs and ACLs of files
86
87       -n|--no-inline
88           disable inlining of small files to metadata blocks, this will
89           decrease the metadata consumption and may help to convert a
90           filesystem with low free space
91
92       -N|--nodesize <SIZE>
93           set filesystem nodesize, the tree block size in which btrfs stores
94           its metadata. The default value is 16KB (16384) or the page size,
95           whichever is bigger. Must be a multiple of the sectorsize, but not
96           larger than 65536. See mkfs.btrfs(8) for more details.
97
98       -r|--rollback
99           rollback to the original ext2/3/4 filesystem if possible
100
101       -l|--label <LABEL>
102           set filesystem label during conversion
103
104       -L|--copy-label
105           use label from the converted filesystem
106
107       -O|--features <feature1>[,<feature2>...]
108           A list of filesystem features turned on at conversion time. Not all
109           features are supported by old kernels. To disable a feature, prefix
110           it with ^. Description of the features is in section FILESYSTEM
111           FEATURES of mkfs.btrfs(8).
112
113           To see all available features that btrfs-convert supports run:
114
115           btrfs-convert -O list-all
116
117       -p|--progress
118           show progress of conversion (a heartbeat indicator and number of
119           inodes processed), on by default
120
121       --no-progress
122           disable progress and show only the main phases of conversion
123

EXIT STATUS

125       btrfs-convert will return 0 if no error happened. If any problems
126       happened, 1 will be returned.
127

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

EXIT STATUS

SEE ALSO