Containerizing Virtual Machines

Recently Google joined hands with Mirantis and Intel to distribute Openstack components in docker containers managed with kubernetes. In the above deployment scenario, each and every component of openstack like nova, neutron, keystone etc.. runs in docker containers and are deployed, managed through kubernetes. I wondered if the nova service is running in a container then how is it going to span a vm instance. An another doubt flashed in my mind that is it possible to run a virtual machine inside a docker container? . The answer is yes but with some prerequisites installed and tweaks done on the docker host. In this post i will show you how to run a vm using kvm in a docker container.

As the docker containers don’t have a kernel of its own and it uses hosts kernel, so it’s not possible to insert kvm kernel module. So instead we will add /dev/kvm and /dev/net/tun devices to the container.

Make sure that you installed docker and kvm on the host. Kvm installation can be tested by

$ kvm-ok

INFO: /dev/kvm exists
KVM acceleration can be used

Run an ubuntu kvm image by the following command

$ docker run -e “RANCHER_VM=true” –cap-add NET_ADMIN -v \
/var/lib/rancher/vm:/vm –device /dev/kvm:/dev/kvm \
–device /dev/net/tun:/dev/net/tun rancher/vm-ubuntu -m 1024m -smp 1

Ubuntu vm which is spannned inside a container gets the ip address of your container. First know the ip address of docker container through the following command

$ docker inspect

ssh into the vm you created above

$ ssh ubuntu@

password: ubuntu