# btrfs-convert

## NAME



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


## SYNOPSIS



           **btrfs-convert**[options] _< device>_
    


## DESCRIPTION



           **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_.
    
           Supported filesystems:
    
           •   ext2, ext3, ext4 — original feature, always built in
    
           •   reiserfs — since version 4.13, optionally built, requires
               libreiserfscore 3.6.27
    
           •   ntfs — external tool **https://github.com/maharmstone/ntfs2btrfs **
    
           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 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).
    
           **BEFORE YOU START**
    
           The source filesystem must be clean, eg. no journal to replay or
           no repairs needed. The respective _fsck_ utility must be run on the
           source filesystem prior to conversion. Please refer to the manual
           pages in case you encounter problems.
    
           For ext2/3/4:
    
               # e2fsck -fvy /dev/sdx
    
           For reiserfs:
    
               # reiserfsck -fy /dev/sdx
    
           Skipping that step could lead to incorrect results on the target
           filesystem, but it may work.
    
           **REMOVE THE ORIGINAL FILESYSTEM METADATA**
    
           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 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**
    
           An optional but recommended step is to run defragmentation on the
           entire filesystem. This will attempt to make file extents 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 32MiB (_-t_).
    
           **ATTEMPT TO MAKE BTRFS METADATA MORE COMPACT**
    
           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(8).
    
               # btrfs balance start -m /mnt/btrfs
    


## OPTIONS



           --csum _< type>_, --checksum _< type>_
               Specify the checksum algorithm. Default is _crc32c_. Valid
               values are _crc32c_ , _xxhash_ , _sha256_ or _blake2_. To mount such
               filesystem kernel must support the checksums as well.
    
           -d|--no-datasum
               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|--no-inline
               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 details.
    
           -r|--rollback
               rollback to the original ext2/3/4 filesystem if possible
    
           -l|--label _< LABEL>_
               set filesystem label during conversion
    
           -L|--copy-label
               use label from the converted filesystem
    
           -O|--features _< feature1>_[,_< feature2>_...]
               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 (a heartbeat indicator and number
               of inodes processed), on by default
    
           --no-progress
               disable progress and show only the main phases of conversion
    
           --uuid _< SPEC>_
               set the FSID of the new filesystem based on _SPEC_ :
    
               •   _new_ - (default) generate UUID for the FSID of btrfs
    
               •   _copy_ - copy UUID from the source filesystem
    
               •   _UUID_ - a conforming UUID value, the 36 byte string
                   representation
    


## EXIT STATUS



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


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