[libvirt] [sandbox PATCH v2 11/19] Image: Add run function

[Cedric Bosdonnat]

On Mon, 2015-08-10 at 17:19 +0100, Daniel P. Berrange wrote:
> On Mon, Aug 10, 2015 at 05:16:19PM +0100, Daniel P. Berrange wrote:
> > On Tue, Aug 04, 2015 at 08:11:17PM +0000, Eren Yagdiran wrote:
> > > Run an already-built template
> > > If there is no execution command specified by user, source.get_command will
> > > find the command to invoke
> > > ---
> > >  virt-sandbox-image/virt-sandbox-image.py | 24 ++++++++++++++++++++++++
> > >  1 file changed, 24 insertions(+)
> > > 
> > > diff --git a/virt-sandbox-image/virt-sandbox-image.py b/virt-sandbox-image/virt-sandbox-image.py
> > > index 4c19fa8..e20ce22 100755
> > > --- a/virt-sandbox-image/virt-sandbox-image.py
> > > +++ b/virt-sandbox-image/virt-sandbox-image.py
> > > @@ -101,6 +101,30 @@ def check_connect(connectstr):
> > >              raise ValueError("%s is not supported by Virt-sandbox" %connectstr)
> > >          return True
> > >  
> > > +def run(args):
> > > +    try:
> > > +        if args.connect is not None:
> > > +            check_connect(args.connect)
> > > +        source = dynamic_source_loader(args.source)
> > > +        diskfile,configfile = source.get_disk(name=args.name,path=args.imagepath)
> > > +
> > > +        format = "qcow2"
> > > +        commandToRun = args.igniter
> > > +        if commandToRun is None:
> > > +            commandToRun = source.get_command(configfile)
> > > +        cmd = ['virt-sandbox']
> > > +        if args.connect is not None:
> > > +            cmd.append("-c")
> > > +            cmd.append(args.connect)
> > > +        params = ['-m','host-image:/=%s,format=%s' %(diskfile,format),
> > > +               '--',
> > > +               commandToRun]
> > > +        cmd = cmd + params
> > > +        subprocess.call(cmd)
> > > +
> > > +    except Exception,e:
> > > +        print "Run Error %s" % str(e)
> > 
> > This code actually ends up launching a sandbox using the template file as
> > the root disk image. This is not good, because we need to be able to run
> > multiple instances of the sandbox, all using the same template file. As
> > such we need to be able to create a new temporary disk image for each
> > sandbox instance, that is an overlay on the main template, an then
> > delete this temporary disk at shutdown.
> 
> Or if we make sure / is read-only that would avoid the problem I
> mention here. With normal docker toolchain is / read-only by
> default, or do they make it writable with a throw-away snapshot ?

They have a layer for the container instance, but it isn't thrown-away
when the container stops as users can commit the changes in that
container's layer to the image template. I think we need to go the
separate temporary layer as you mentioned, and have either an
automatically computed container name or one defined by the user: with
that we should have clean separation for all instances.

--
Cedric