I’m not sure if snap developers monitor launchpad or not, so I thought I’d report LP bug #1867415 here as well:
Boot with e.g. the current ubuntu-20.04-desktop-amd64.iso. Open a terminal and run
df -h. You’ll notice:
Filesystem Size Used Avail Use% Mounted on /cow 2.0G 434M 1.5G 23% /
This means that the tmpfs file system needs 400 MB RAM for snaps. Xenial didn’t have snaps and needed only 14 MB tmpfs. Snap shouldn’t consume tmpfs RAM space, it should only use squashfs disk space.
I think this is caused by function Install() in snap/squashfs/squashfs.go, which hardlinks /var/lib/snapd/seed/snaps/* to /var/lib/snapd/snaps/*.
Hardlinks cause overlayfs copy-ups in live CDs and LTSP.
Maybe the next option, symlinks, should be preferred in overlayfs.