Change root subvolume on btrfs

[piorunz <piorunz@gmx.com>]

Hello,

I have / partition on btrfs subvolume, default name @rootfs created by
Debian.

I'd like to use Timeshift for snapshots, but it only recognizes root on
@ subvolume, any other subvolume name is being ignored. Pretty stupid to
me, but I'd like to use it - I don't see other way to have snapshots.

Question:
How can I rename / subvolume on btrfs from @rootfs to @?
I tried:
rename folder name by hand from USB stick Linux Mint from @rootfs to @,
and then changing @rootfs to @ in /etc/fstab, but grub didn't booted, it
thrown me out to grub emergency console. I had to revert it back.

What else I need to do to make this change? Chroot to debian and do sudo
update-grub? If so, how? There is many conflicting tutorials how can I
chroot to do update-grub that I am lost. I will welcome any suggestions.

Some context:
$ sudo btrfs subvolume list /
ID 256 gen 176714 top level 5 path @rootfs
ID 265 gen 21191 top level 256 path var/lib/portables
ID 266 gen 21192 top level 256 path var/lib/machines

/etc/fstab lines:

UUID=77ba5989-5d64-4929-9145-ede6751a4102       /
        btrfs
noatime,nodiratime,space_cache=v2,ssd,compress-force=zstd:6,subvol=@rootfs
0 1
(...)
UUID=9A94-D623                                  /boot/efi
        vfat    umask=0077 0 1

I use UEFI with GPT, no CSM, it that matters for anything.


--
With kindest regards, Piotr.

⢀⣴⠾⠻⢶⣦⠀
⣾⠁⢠⠒⠀⣿⡁ Debian - The universal operating system
⢿⡄⠘⠷⠚⠋⠀ https://www.debian.org
⠈⠳⣄⠀⠀⠀⠀