lsblk: root partition mounted on / and /var/snap/firefox/common/host-hunspell?

Question

I rebooted ubuntu 22.04 today and it could not find the root drive and I kept being dropped to a root shell. Correlation does not prove causality, but I find it very odd that nvme0n1p5 is mounted at both / (correct) and /var/snap/firefox/common/host-hunspell (incorrect). Not sure if this is a mount/fstab thing or a snap thing or what...

$ lsblk 
│                                     
├─nvme0n1p4 259:4    0     1G  0 part 
├─nvme0n1p5 259:5    0  29.3G  0 part /var/snap/firefox/common/host-hunspell
│                                     /
├─nvme0n1p6 259:6    0   8.2G  0 part [SWAP]

I changed fstab to use the PARTUUID instead of the UUID and it finally booted, but I would like to address this issue.

$ snap list
Name                            Version             Rev    Tracking         Publisher   Notes
bare                            1.0                 5      latest/stable    canonical✓  base
core20                          20220826            1623   latest/stable    canonical✓  base
firefox                         105.0-2             1860   latest/stable/…  mozilla✓    -
gnome-3-38-2004                 0+git.891e5bc       115    latest/stable/…  canonical✓  -
gtk-common-themes               0.1-81-g442e511     1535   latest/stable/…  canonical✓  -
hunspell-dictionaries-1-7-2004  1.7-20.04+pkg-6fd6  2      latest/stable    brlin       -
snap-store                      41.3-64-g512c0ff    599    latest/stable/…  canonical✓  -
snapd                           2.57.1              16778  latest/stable    canonical✓  snapd
snapd-desktop-integration       0.1                 14     latest/stable/…  canonical✓  -

Answer 1

Below command removes the extra binding instantly:

snap disconnect firefox:host-hunspell

The dual binding is not harmful nor a bug, but looks un-linux to me.

Answer 2

As indicated over at the snapcraft forum, this mount is set up to allow Firefox Snap to use the spell check dictionaries (hunspell) of the main system. A discussion about this commit is available here.

Answer 3

I had a concern about the Firefox snap binding as it was showing up in the output of one of my aliases, for showing data usage and availability of mounted drives:

alias list-size='df -ahT --type=ext4 --type=vfat --type=ntfs --type=fuseblk --type=swap'

I have many LVM volumes, for which I create temporary snap partitions to preserve data integrity when I do a backup. I had found out the hard way that if the backup program inadvertently ends, one of these snap partitions could remain dangling, along with the associated snapshot functionalities. This can lead to the underlying LVM volume corrupting, and if it's part of my running system, can corrupt other volumes as well, leading to all of my Linux distros becoming nonoperational and a need to recreate LVM volumes and operating systems from backup. So I keep an eye out and am very wary of volumes suddenly appearing with "snap" in the name.

Well, I can accept your admonition that this extraneous Firefox binding is not a snapshot volume that I need to worry about. If I don't need to worry about it, I don't even need to know it's there, as with other volumes. I can take the "-a" option out of my alias and it still lists my mounted volumes, including my bindings, without showing the Firefox binding.

alias list-size='df -hT --type=ext4 --type=vfat --type=ntfs --type=fuseblk --type=swap'

I also have a function alias for lsblk which I call list-dev, which doesn't show the Firefox binding, so all is well again.

function list-dev () {
if [[ ${#} -eq 1 ]]; then
    lsblk -e7 -o NAME,FSTYPE,SIZE,LABEL,MOUNTPOINT,UUID "/dev/${1}"
else
    lsblk -e7 -o NAME,FSTYPE,SIZE,LABEL,MOUNTPOINT,UUID
fi