[Lxc-users] [systemd-devel] Unable to run systemd in an LXC / cgroup container.

[Michael H. Warfield]

On Sat, 2012-10-27 at 13:51 -0400, Michael H. Warfield wrote:
> On Sat, 2012-10-27 at 13:40 -0400, Michael H. Warfield wrote:
> > /me erasing everything at this point and taking off the systemd crew,
> > since this will have no relevance to them...
> > 
> > Testing the hook feature out using git rev (finally got it built)...
> > 
> > I added this line to my config...
> > 
> > lxc.mount.entry=tmpfs /srv/lxc/private/Plover/dev.tmp tmpfs defaults 0 0
> > lxc.hook.mount = /var/lib/lxc/Plover/mount
> > 
> > In /var/lib/lxc/Plover/mount I have this:
> > 
> > -- 
> > rsync -avAH /srv/lxc/private/Plover/dev.template/. /srv/lxc/private/Plover/dev.tmp/
> > -- 
> 
> > (This is just testing out the concepts.
> 
> > If I understand this correctly, lxc.hook.pre-mount runs BEFORE the
> > mounting takes place and lxc.hook.mount takes place after the mount.
> 
> > Problem is, the result of that rsync is not showing up in the mounted
> > tmpfs file system but is showing up in the underlying parent file system
> > as if it were run pre-mount.  Something not right here...

> I changed it to "lxc.hook.start = /srv/lxc/mount" (where I put the
> script in the container) which then works but that then requires the
> template and the command to be in the container.  Suboptimal to say the
> least.  But it gives me a way to test this tmpfs thing out.

> I also noticed that the .start hook runs, it appears, after caps are
> dropped and I see a lot of bitching about mknod on certain devices.  I
> had to thrown an exit 0 into that script so it would continue in spite
> of the errors but, now, I can refine my template based on what it could
> create.

Crap.  I've got a catch-22 here...  This is going to take some work.

Yes, we can create the /dev directory with tmpfs from a template.
Problem is that /dev/pts does not exist at the time we need to mount the
devpts on /dev/pts for the pty's so that hurls chunks and dies.  We
can't create the /dev/ directory contents prior to mounting in the
pre-mount hook because we won't have tmpfs in place at the time.  We
have to get tmpfs mounted on /dev and then create /dev/pts and then
mount the ptys in there.  There has to be a mkdir in between those two
mount actions.  Simplest solution would seem to be to add some logic to
the mount logic that says "test if directory exists and, if not, create
it."  I'm not sure of the consequences of that, though.

I don't see a way to make this happen with hooks.  It's almost like we
need and on-mount per mount hook.

> > Regards,
> > Mike
> 
> Regards,
> Mike

Regards,
Mike
-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
 PGP Key: 0x674627FF        | possible worlds.  A pessimist is sure of it!
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