Ubuntu – How to enable btrfs zstd compression

btrfs will compress every file changed since it was mounted if you use:

mount -o compress-force=lzo /dev/btrfsdev /mnt/btrfsmnt

If you want to see to it that ALL files get compressed this way, I've got a little script I wrote to do it...

du -ht +$((1024*1024)) "$HOME" |\
    sed -rn 's/^[^/]*(.*)/btrfs fi defrag -fvclzo "\1"/p' |\
        sudo sh -n

The above only works on my $HOME directory - but you can use it on anything or everything as you like. It's also got the -n operand fed to sh as is so you can see for yourself what sh is currently not doing before removing it to tell it to do it.

Anyway, first it queries du for files in human-readable format (probably redundant here since we strip that in the next step anyway) that are larger than 1MB or $((1024*1024)).

It |pipes its info to sed which strips off everything before the leading /, "quotes" the filename, builds the btrfs filesystem defragment -verbose -flush-to-disk -compress-lzo \filename command and hands it over a |pipe to sudo sh to execute.

Again, it won't do anything so long as sh --no-execute is in effect, though.

I think some very recent btrfs userspace tool builds do defragment entire directories recursively, but if so it's a pretty new thing, so I've always had to do stuff like this.

In Debian/Ubuntu:

apt install btrfs-compsize
compsize /mnt/btrfs-partition

In Fedora:

dnf install compsize
compsize /mnt/btrfs-partition

output is like this:

Processed 123574 files, 1399139 regular extents (1399139 refs), 69614 inline.
Type       Perc     Disk Usage   Uncompressed Referenced  
TOTAL       73%      211G         289G         289G       
none       100%      174G         174G         174G       
lzo         32%       37G         115G         115G