Tuesday, 21 August 2018

Re: Transition of LXD from deb to snap

On Tue, Aug 21, 2018 at 12:25:33PM -0700, Steve Langasek wrote:
> On Tue, Aug 21, 2018 at 03:03:48PM -0400, Stéphane Graber wrote:
> > > > A branch of the stable channel of those tracks will be created and
> > > > closed per policy on seeded snaps (allowing to push emergency snaps to
> > > > those users bypassing the upstream).
> > > Excellent!
> > I actually had a question about that part, the wiki says to create an
> > ubuntu-18.10 branch and use that during snap installation.
> > But then what's responsible for switching this to a ubuntu-19.04 branch
> > during the next upgrade?
> Support for this has landed in ubuntu-release-upgrader 1:18.10.8 in cosmic;
> LP: #1748581. Note that this is based on a whitelist of known seeded snaps
> that are encoded in u-r-u as part of the quirks handling (which is not ideal
> since it duplicates the package seeds), so this will need to be updated to
> include the lxd snap here.

Hmm, interesting, though it looks like the logic in the upgrader here is
a bit lacking and may lead to data corruption or at least broken snaps.

It appears to just run "snap refresh <name>
--channel=stable/ubuntu-18.10" which means a potential track switch and
channel switch for users that have seen decided to switch to another
channel or track.

Commented in the bug, I suspect this bug needs to be re-open and the
logic revisited.


> > Since the same version of the snap will be pushed to all Ubuntu series,
> > wouldn't it make more sense to have it just be "ubuntu", saving us the
> > trouble of having to figure out what to do on Ubuntu release upgrades
> > and reflecting the fact that the snap is the same for all series.
> This escape hatch exists precisely for the case that the upstream stable
> snap does not integrate correctly in a release-agnostic fashion and
> per-Ubuntu-release quirking is needed. Better to have it and never use it
> than to need it and not have it.

Yeah, if we fix the upgrader to handle the above properly
(and as suggested in the LP bug), then that should be fine.

Stéphane Graber
Ubuntu developer