I’m happy to inform you guys that I successfully installed lxc-clone (via LuCi) and:
-
Created a clone of an existing container (explicitly making it use a BTRFS backing store):
lxc-clone -B btrfs <original-name> <clone-name>
-
After that I was able to make (near-instant) snapshots using regular LXC tooling:
lxc-snapshot -n <clone-name>
The second command refers to the “Clone-name” because I had to clone the original to a BTRFS backed one in step one, if the container was created using a BTRFS backing store to begin with then step one can be omitted of course).
So THANKS fly out to @cynerd for making rsync with extended attributes available on out systems! Which (amongst other things) resulted in the option for near-instant snapshots of near-zero size!
I do have a remaining/follow-up question though.