I've been following a set of steps very similar to the ones mentioned on the ArchWiki installation guide.

I've recently started playing around with BTRFS snapshots, particularly of the / subvolume.

During installation, my mount command looks something like this:

mount -o noatime,nodiratime,compress=lzo,space_cache,subvol=@ /dev/sda3 /mnt

(considering /dev/sda3 is the BTRFS partition containing all my system subvolumes).

genfstab produces an /etc/fstab in the below fashion:

# /dev/sda3
UUID=<long-uuid>    /    btrfs    rw,noatime,nodiratime,compress=lzo,space_cache,subvolid=256,subvol=/@,subvol=@  0  0

As you can see in the above snippet, it automatically adds the parameter for subvolid and also one more for a repeat subvol (which I don't care at this point).

The confusing part begins when I restore to a previous snapshot with commands like:

mount /dev/sda3 /mnt
mv /mnt/@ /mnt/<some-random-name>
mn /mnt/<an_old_snapshot_name> /mnt/@

it leaves the /etc/fstab file intact, which is OK in a sense if you consider that rather than changing the file, I renamed my subvolumes in a way that the same name now refers to a different subvolume, but what I'm confused about is the old subvolid, which even though remains unchanged, let's the right subvolume being mounted.

To summarize: does a different subvolid and subvol references not cause any issue while mounting volumes?

PS: I apologize for such a lengthy question and apparently also for a noob question, but couldn't find an answer by myself.


As mentioned in this comment on Reddit, subvolid can be safely removed to make the references consistent.

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