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

[Gao feng]

On 01/21/2014 01:59 AM, Daniel P. Berrange wrote:
> 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.

Sorry for another question, lxc-enter-namespace is unavailable on the remote machine,
you can't use virsh -c lxc+ssh://root@x.x.x.x/ lxc-enter-namespace $CONTAINER /path/to/command/to/run arg1 arg2.

I want to know what's the major handicap that we cannot support lxc-enter-namespace on
remote machine.

Thanks!