tuna, 19 days ago

I think it is so that the subvolume can be mounted with different options. You can of course have a mixed layout which might be more convenient, so that say root and home subvolumes mount with the same options, but swap mounts with different options. And the top level never gets mounted at all.

<span style="color:#323232;">toplevel (not mounted)
</span><span style="color:#323232;">+-- @ (subvolume mounted on /)
</span><span style="color:#323232;">    +-- home (subvolume, looks like a folder, same mount options as @)
</span><span style="color:#323232;">    +-- usr (folder, gets snapshotted by @)
</span><span style="color:#323232;">    +-- ...
</span><span style="color:#323232;">+-- @swap (subvolume with different options, mounted on /swap)
</span>

I set mine up with a purely flat layout so I haven’t verified this is true, but it sounds reasonable.

Here’s the documentation I was looking at:

web.archive.org/web/…/SysadminGuide#Flat