libvirt users - Apr 2017 - Re: creating a lxc image to be used with libvirt-lxc

Dear all,

I'm moving my first baby steps with libvirt-lxc trying to convert over from
an LXD installation and one of the hurdles is putting together an image.

All the examples I found about libvirt-lxc refer to running /bin/sh in a
container, almost as if it was docker, as opposed to run a "full
system"
like I've been doing with lxd. Also virt-install, often referred in libvirt
docs, seems to be specific/only for kvm.

Can anybody point me to any documentation to achieve the same as you'd do
with lxd? would it even just work to use those images (
https://cloud-images.ubuntu.com/) with libvirt? Last but not least, is
there any way to "publish" a modified image so that I could make
changes to
any of the above and then reuse the modified one as a base for other
containers?

thank you,

spike

On Mon, Apr 03, 2017 at 05:52:33PM +0000, Spike wrote:
> Dear all,
> 
> I'm moving my first baby steps with libvirt-lxc trying to convert over
from
> an LXD installation and one of the hurdles is putting together an image.
> 
> All the examples I found about libvirt-lxc refer to running /bin/sh in a
> container, almost as if it was docker, as opposed to run a "full
system"
> like I've been doing with lxd. Also virt-install, often referred in
libvirt
> docs, seems to be specific/only for kvm.
> 
> Can anybody point me to any documentation to achieve the same as you'd
do
> with lxd? would it even just work to use those images (
> https://cloud-images.ubuntu.com/) with libvirt? Last but not least, is
> there any way to "publish" a modified image so that I could make
changes to
> any of the above and then reuse the modified one as a base for other
> containers?
Libvirt LXC doesn't really care what you run inside the containedr - it is
possible to use it to run a single application (docker style), or to run a
full operating system. You essentially just need to populate a chroot with
the operating system install you want to run.

I've previously tested with a Fedora chroot:

 
https://www.berrange.com/posts/2013/08/12/running-a-full-fedora-os-inside-a-libvirt-lxc-guest/

If you want to have layered modifications, then the best bet is probably
to make use of overlayfs with your chroots. ie populate a base chroot
and treat it as read-only thereafter. Then create a new directory mounted
with overlayfs to add a writable layer on top.


Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/ :|

ok, thank you Daniel, that helps, I'll see if I can adapt it to other OS
and figure out the docker style stuff, it would be useful to run a few
things I have in mind.

Btw, Daniel, have you ever tried to run libvirt inside a container? I was
trying to do so to test things since I didn't want to get all the stuff
installed on the host, but I got a whole bunch of errors and virt-manager
would not connect no matter what.

Also, some more examples, if anybody on the list has them, would be most
appreciated to help a noob get started.

best,

Spike

On Tue, Apr 4, 2017 at 2:59 AM Daniel P. Berrange <berrange@redhat.com>
wrote:
> On Mon, Apr 03, 2017 at 05:52:33PM +0000, Spike wrote:
> > Dear all,
> >
> > I'm moving my first baby steps with libvirt-lxc trying to convert
over
> from
> > an LXD installation and one of the hurdles is putting together an
image.
> >
> > All the examples I found about libvirt-lxc refer to running /bin/sh in
a
> > container, almost as if it was docker, as opposed to run a "full
system"
> > like I've been doing with lxd. Also virt-install, often referred
in
> libvirt
> > docs, seems to be specific/only for kvm.
> >
> > Can anybody point me to any documentation to achieve the same as
you'd do
> > with lxd? would it even just work to use those images (
> > https://cloud-images.ubuntu.com/) with libvirt? Last but not least, is
> > there any way to "publish" a modified image so that I could
make changes
> to
> > any of the above and then reuse the modified one as a base for other
> > containers?
>
> Libvirt LXC doesn't really care what you run inside the containedr - it
is
> possible to use it to run a single application (docker style), or to run a
> full operating system. You essentially just need to populate a chroot with
> the operating system install you want to run.
>
> I've previously tested with a Fedora chroot:
>
>
>
https://www.berrange.com/posts/2013/08/12/running-a-full-fedora-os-inside-a-libvirt-lxc-guest/
>
> If you want to have layered modifications, then the best bet is probably
> to make use of overlayfs with your chroots. ie populate a base chroot
> and treat it as read-only thereafter. Then create a new directory mounted
> with overlayfs to add a writable layer on top.
>
>
> Regards,
> Daniel
> --
> |: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/
> :|
> |: http://libvirt.org              -o-             http://virt-manager.org
> :|
> |: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/
> :|
>