Deduplicate data by creating reflinks between identical files.
$ cargo install reflicate
$ export PATH=$PATH:~/.cargo/bin
This is an alpha quality software. Feel free to test this program on your system and report bugs. But remember to make a backup first.
reflicate [<directories...>] [-d] [-h] [-i <indexfile>] [-p] [-q]
Positional Arguments:
directories directories to deduplicate
Options:
-d, --dryrun do not make any filesystem changes
-h, --hardlinks make hardlinks instead of reflinks
-i, --indexfile store computed hashes in indexfile and use them in subsequent runs
-p, --paranoid compute sha256 hashes in addition to blake3 hashes
and do not trust precomputed hashes from indexfile
-q, --quiet be quiet
Reflicate scans the specified directories for identical files and reflinks them together. Files are considered identical when they have the same size and equal blake3 hash. Reflinked files share the same disk blocks, so disk space is only occupied once. On edit a file is copied into different blocks, so it's safe to reflink files that currently have the same content but may differ in the future.
Hardlinks differ from reflinks in two ways:
- Hardlinks are supported by virtually all posix filesystems, while reflinks are only supported by a few, eg XFS, BTRFS, OCFS2.
- Hardlinks share the same inode, so hardlinked files are always edited together.
Reflicate stores four values in the indexfile: file paths, file sizes, modification times, and blake3 hashes. On subsequent runs, it computes hashes only for files that have different size or modification time. This mean the program can run faster when indexfile is used.
Internally indexfile is combination of CDB (constant database) and msgpack. This means that indexfile will be overwritten on subsequent runs, so if you reflicate different directories, use a different indexfile.
By default reflicate computes and compares blake3 hashes, but in paranoid mode sha256 hashes are used as well. Additionally, in paranoid mode all hashes are always computed because it is possible to manipulate file modification time.
Systemd timer can be used to run periodically. To do this, you need to run the following commands:
$ mkdir -p ~/.config/systemd/user/
$ cp systemd/* ~/.config/systemd/user/
$ systemctl --user daemon-reload
$ systemctl --user enable reflicate.timer
By default, the periodic task runs weekly and reflicate your home directory.
You can adjust this to your needs by editing the reflicate.service and reflicate.timer files.
At the beginning let's create an XFS file system, mount it, and create a test directory.
$ dd if=/dev/zero of=test.img bs=1M count=100
$ mkfs.xfs test.img
$ sudo mount -o loop test.img /mnt
$ sudo mkdir /mnt/test
$ sudo chown `id -u` /mnt/test
Then create two identical files and two different one.
$ dd if=/dev/zero of=/mnt/test/file1 bs=1M count=10
$ dd if=/dev/zero of=/mnt/test/file2 bs=1M count=10
$ dd if=/dev/zero of=/mnt/test/file3 bs=1M count=12
$ dd if=/dev/zero of=/mnt/test/file4 bs=1M count=15
Now we see that 53 MiB of disk space is occupied (including metadata).
$ df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/loop0 95M 53M 42M 56% /mnt
Let's reflicate the test directory.
$ reflicate /mnt/test/
/mnt/test/file2 => /mnt/test/file1 [10 MiB]
10 MiB saved
And we see that currently only 43 MiB of disk space is occupied.
$ df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/loop0 95M 43M 52M 46% /mnt
Let's break the reflink and create file2 with the same content as file3.
$ dd if=/dev/zero of=/mnt/test/file2 bs=1M count=12
$ df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/loop0 95M 55M 40M 59% /mnt
Then reflicate the test directory again.
$ reflicate /mnt/test/
/mnt/test/file3 => /mnt/test/file2 [12 MiB]
12 MiB saved
$ df -h /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/loop0 95M 43M 52M 46% /mnt
At the end, let's remove the test filesystem.
$ sudo umount /mnt
$ rm test.img