[lxc-devel] lxc-clone rewrite

[Stéphane Graber]

On Mon, Aug 31, 2015 at 01:43:07PM +0000, Serge Hallyn wrote:
> Quoting Christian Brauner (christianvanbrauner at gmail.com):
> > On Fri, Aug 28, 2015 at 12:46:17AM +0200, Christian Brauner wrote:
> > > On Thu, Aug 27, 2015 at 03:41:03PM -0400, Stéphane Graber wrote:
> > > > On Sun, Aug 16, 2015 at 04:46:31PM +0000, Serge Hallyn wrote:
> > > > > Quoting Christian Brauner (christianvanbrauner at gmail.com):
> > > > > Hey,
> > > > > 
> > > > > I'll leave this to Stéphane, as he's pretty keen on leaving the # commands
> > > > > low.  As you say we might eventually be able to deprecate lxc-clone, and
> > > > > lxc-copy might eventually be a nice hook for migration.
> > > > 
> > > > That'd be fine with me I think, bonus point if we can somehow merge
> > > > lxc-start-ephemeral in there and kill two birds with one stone
> > > > (lxc-clone & lxc-start-ephemeral).
> > > > 
> > > > The timeline for this would be having lxc-copy in 1.2 with both
> > > > lxc-clone and lxc-start-ephemeral doing arg swapping + re-exec tricks
> > > > with a warning that they'll go away for good in 2.0.
> > > > 
> > > > How does that sound?
> > > 
> > > Sounds good! I'm on it!
> > > 
> > > Christian
> > 
> > In the current python implementation of lxc-start-ephemeral we generate a
> > pre-mount and post-stop script. The post-stop script seems to be used to destroy
> > the container. For the rewrite in C and the merge with lxc-clone I thought about
> > using a simple snapshot-clone with c->clone() with a random name, start it
> > c->start() and when the container is shutdown destroy it with c->destroy().
> > This seems cleaner to me then generating scripts. Are there any reasons to not
> > do it this way? And if so what would you prefer?
> 
> If you can do this robustly and cleanly then I prefer this.

The reason was that the container could be started backgrounded (-d) in
which case lxc-start-ephemeral wasn't around anymore to clean things up
when the container exits.

The post-stop method ensured that the container would be destroyed
whenever it finally dies and regardless of how it was killed (either
shutdown from inside the container or lxc-stop/lxc-destroy).

-- 
Stéphane Graber
Ubuntu developer
http://www.ubuntu.com
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