btrfs, ostree, systemd-nspawn creating subvolumes for containers

[Chris Murphy <lists colorremedies com>]

Hi,

Does anyone know off hand what the interaction is between ostree and
systemd on btrfs when creating new ostrees and doing rollbacks? I
haven't tested this myself yet.

On btrfs, systemd now always creates btrfs subvolumes in
/var/lib/machines for nspawn containers. So I wonder how ostree (or
rpm-ostree if there's a difference in behavior) deals with those
nested subvolumes when creating new trees? And how are rollbacks
handled also?

I fairly strongly feel like nested btrfs subvolumes aren't a good
idea. I think there should instead be a systemd-machines subvolume at
the top level of the filesystem, and use fstab to mount it at
/var/lib/machines. And then exempt it from ostree doing anything with
the contents, just like ostree does not decend into /home.

Otherwise, I think we're asking for confusion...


-- 
Chris Murphy