Re: Running an ostree deployment in a container

Hey !

On 04/26/2018 04:16 AM, Colin Walters wrote:

On Wed, Apr 25, 2018, at 6:22 AM, Arnaud Rebillout wrote:
Dear OSTree maintainers,

I'm attempting to build a basic Debian Stretch OS with OSTree. 
Cool.  Is this for a server use case?  Desktop?  Embedded?  The answer
to that informs a bit how you do testing.

Desktop, GNOME based.

So far so good, I end up with my "deployment" directory, and now I would
like to test it in a container or a VM.

I noticed that the man page of 'systemd-nspawn' gives an example for
running an OSTree deployment [1]. Plus, Philip Withnall added the
'--pivot-root' option in Feb. 2017 for that purpose [2]. So I thought
I'd give it a try.
I haven't played with nspawn for this much personally.  In rpm-ostree
we actually run each rpm script (%post) etc. in a bwrap container
inside the target root.  

The code is mostly here:

That said this is probably more useful for a quick test:

Thanks a lot for the links. I hear a lot about bwrap but I didn't tried
it yet, maybe now is the time :)

And, to be a bit more general, what's the guidelines to test a
deployment locally? Looking at containers, systemd-nspawn seems to be
the way to go, it's a one-liner (almost). 
One reason I prefer bwrap over nspawn is that bwrap is nestable (container in container)
a lot more nicely.  This has come up in our CI, which uses Kubernetes.
We haven't yet plumbed everything through there to make it work, but
it's on our near term radar.  (Actually the main blocker right now is our
SELinux policy denies e.g. mount() inside containers today)

Good to know, thanks for sharing.

Looking at virtual machines
however, I struggled a lot with QEmu, but didn't come up with a
straightforward solution to create a bootable image out of my deployment
directory. Not yet. But maybe I just need to learn my qemu-fu better ;)
Most of our testing for Atomic Host today rebases/upgrades existing cloud
images.   You could almost certainly take e.g. a FAH cloud image and add 
a remote to your repo, and `ostree admin switch` to it.   (rpm-ostree
currently barfs on trees which don't contain an rpmdb, we may fix it someday)

That opens the question though to how one generates a cloud image/ISO/etc.
For Fedora-derived OSes we use Anaconda which supports ostree now.
In fact, it's highly likely that you could use Anaconda to install your ostree
content, even though it's Debian; I tried to support that use case theoretically,
though see:

You can also probably dig a bit and find the different image building tools
from the various libostree users linked in the  I searched
briefly and found:

When I was first developing ostree I wrote some code which used libguestfs:
That path has some neat advantages but also disadvantages.

Anyways at a practical level I'd try to find Endless' installer code as it's
probably the closest match to what you're doing.

Yep, Endless tooling is my starting point on that, I would like to
leverage the existing Debian tooling as much as possible, so I start
looking in this direction first. There's plenty of things available,
building an image from scratch is not the issue.

Thanks for all your answers!


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