[libvirt] What is the robust/recommended way to retrieve the PID of a VM's init process ?

[Daniel P. Berrange]

On Mon, Jan 20, 2014 at 06:53:28PM +0100, Thierry Parmentelat wrote:
> Hi
> 
> Well if I need to run anything in the container context, short of entering
> it through e.g. ssh - hoping this is properly set up - well, I can’t..
> 
> I am using libvirt / lxc to set up a build box; essentially every night
> I would spawn a set of fresh VMs of some flavours (fedora18, ubuntu,
> what not) and use this to rebuild my system from scratch
> In this context it’s a real hassle to have to even set up ssh, there is
> no good reason for the build VM to run an ssh service at all, and I am
> concerned it might pull dependencies that I do not need/want
> I’d much rather have a direct means to just run some command inside the container.
> 
> Admittedly I’m brain-damaged after having used vservers for too long, and their
> ‘vserver <container> exec command to run’ feature is in my genes now ;)
> 
> Now maybe I am the one who is missing something and there already is something to do that ?
> Using the trick below I essentially have what I need mind you, I’m just concerned that it
> kind of works by accident :-)

Yes, it already exists, albeit as a lxc specific custom command/api:

  $ virsh lxc-enter-namespace $CONTAINER /path/to/command/to/run arg1 arg2...

There's a corresponding API in the libvirt-lxc.so library
virDomainLxcEnterNamspace

Eventually we'll turn this into a proper libvirt API with a less sucky
virsh command name.

Daniel
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