no recognition of proper btrfs layout when using labels in fstab

[RouL]

Describe the bug
timeshift doesn't recognize proper btrfs layout, if labels are used in fstab instead of UUIDs

To Reproduce

• setup Ubuntu 22.04 LTS with btrfs and configure the fstab with labels instead of uuids (see below)
• install timeshift
• configure timeshift (no error during configuration!)
• try to make your first snapshot
• => message indicating unsupported fs layout

doesn't work:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system>    <mount point>   <type>  <options>                                       <dump>  <pass>
LABEL=system       /               btrfs   defaults,noatime,compress=zstd:3,subvol=@       0       1
LABEL=boot         /boot           ext4    defaults                                        0       2
LABEL=ESP          /boot/efi       vfat    umask=0077                                      0       1
LABEL=system       /.swap          btrfs   defaults,noatime,subvol=@swap                   0       2
/.swap/swapfile    none            swap    defaults                                        0       0
LABEL=system       /var/log        btrfs   defaults,noatime,compress=zstd:3,subvol=@log    0       2
LABEL=system       /var/cache      btrfs   defaults,noatime,compress=zstd:3,subvol=@cache  0       2
LABEL=system       /var/tmp        btrfs   defaults,noatime,compress=zstd:3,subvol=@tmp    0       2
LABEL=system       /home           btrfs   defaults,noatime,compress=zstd:3,subvol=@home   0       2

does work:

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system>    <mount point>   <type>  <options>                                       <dump>  <pass>
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /               btrfs   defaults,noatime,compress=zstd:3,subvol=@       0       1
UUID=3926c20d-4ef1-4448-ab29-5cd84e887994       /boot           ext4    defaults                                        0       2
UUID=F999-ADE8                                  /boot/efi       vfat    umask=0077                                      0       1
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /.swap          btrfs   defaults,noatime,subvol=@swap                   0       2
/.swap/swapfile                                 none            swap    defaults                                        0       0
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /var/log        btrfs   defaults,noatime,compress=zstd:3,subvol=@log    0       2
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /var/cache      btrfs   defaults,noatime,compress=zstd:3,subvol=@cache  0       2
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /var/tmp        btrfs   defaults,noatime,compress=zstd:3,subvol=@tmp    0       2
UUID=6f975e3c-6fe5-4c5f-81d6-16df041b2a63       /home           btrfs   defaults,noatime,compress=zstd:3,subvol=@home   0       2

output of lsblk -o +LABEL /dev/mmcblk0

NAME        MAJ:MIN RM  SIZE RO TYPE  MOUNTPOINTS                            LABEL
mmcblk0     179:0    0 57,6G  0 disk
├─mmcblk0p1 179:1    0  524M  0 part  /boot/efi                              ESP
├─mmcblk0p2 179:2    0  1,7G  0 part  /boot                                  boot
└─mmcblk0p3 179:3    0 55,4G  0 part                                         cryptsystem
  └─system  253:0    0 55,4G  0 crypt /run/timeshift/backup                  system
                                      /var/tmp
                                      /var/log
                                      /var/cache
                                      /.swap
                                      /home
                                      /var/snap/firefox/common/host-hunspell
                                      /

Expected behavior
proper recognition of of btrfs layout no matter if UUID, LABEL, PARTLABEL, PARTUUID or /dev/[...] is used

System:

• Ubuntu 22.04 LTS
• Gnome 42.5
• Timeshift 21.09.1

[shuuji3]

I also encountered the same issue when using LABEL= for partitions, and It was difficult to spot the actual issue. I wanted to manage the partitions with LABEL since it's more human-readable.

For reference, a similar issue was reported in the previous repository: teejee2008/timeshift#828.

[DJCrashdummy]

just my 2 cents: i would use paths instead of labels because they are also human readable and - as long as you don't fiddle around with your hardware - less error prone. ...and IIRC Timeshift should work fine with paths. 😁
another option would be to still use UUIDs and simply add the Label at the end of each line as a comment. 🤷

@RouL for a btrfs file system any value - except 0 - for <pass> in the 6th column of the /etc/fstab makes no sense.
BTW: if this is your whole /etc/fstab, i would use tmpfs for /tmp or at least a separate subvolume, to exclude it from the snapshots.