[lxc-users] unable to start qemu-kvm inside lxc container (the host freezes)

[Serge Hallyn]

Quoting Syraxes (syraxes at gmail.com):
> Hello,
> 
> I am trying to start a qemu virtual machine inside a LXC container
> 
> (one might wonder why exactly would I want to do this.  The idea is
> that I have a complex environment with 6 virtual machines + network
> bridges + mysql + some proprietary software ,    and the goal is to
> start multiple environments on a computer .  We need processes and
> network isolation between the environments.    So starting one qemu is
> only the first step ... )
> 
> 
> The host is a CentOS 6.6 ,  and the container is also CentOS 6.6 .
> 
> Inside the container,  the qemu complained that there is no  /dev/kvm
> and  /dev/net/tun  .
> So I've created them with mknod   and also added into the container config :
> lxc.cgroup.devices.allow = c 10:232 rwm          #   the /dev/kvm
> lxc.cgroup.devices.allow = c 10:200 rwm          #   the /dev/net/tun
> 
> 
> After these changes,  when I try to start the qemu vm   the host
> computer freezes .
> 
> Any idea about what am I doing wrong ?
> I guess that it's incorrect to give the container access to those
> devices.

No, it's fine.

> But is there another way to make the qemu work inside the
> lxc container ?

Yes.  I've done it many times.  The host freezing suggests you
have a problem with the kvm binary - kvm runs fine outside of
a container?  You're sure you have the same arch in the container
as on the host?  If you strace kvm in the container, does it
give you any clues?