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If you created your BTRFS filesystem a little while ago you might not have no_holes support which is simply an improvement that can be added and reduces the size metadata consumes on the disk. You can check if your filesystem has it in 2 ways:


sudo btrfs inspect-internal dump-super /dev/nvme0n1p2

where /dev/<disk> is what you want to check.

Output is as follows:

As you can note, NO_HOLES is listed under incompat_flags.

Another method is to check via the UUID in this way:

ls /sys/fs/btrfs/383732b1-5e87-4b68-a15a-f044bc559877/features/

As we can see no_holes is also listed here.

To add no_holes support the disk must be UNMOUNTED. This might mean you have to boot off a live CD like an ubuntu live ISO from a USB stick.

Once you have unmounted the filesystem you can easily add no_holes support with the -n flag as such:

sudo btrfstune -n /dev/nvme0n1p2

Note, as that disk housed my root partition I had to use a live CD in order to run the command successfully then reboot back into my system afterwards.

This completes how to add the no_hole improvement to a filesystem made prior to v5.15 when it became the default.

start/noholesbtrfs.txt · Last modified: 2023/09/14 20:48 by peter