Docker

Docker is a convenient tool when setting up an operating system. But, at the end of the process, sometimes we want to run this operating system on a real machine, instead of a container. With debootstick, we can achieve this easily. The idea is to export the filesystem content of a container and use it as input of debootstick.

Exporting the filesystem tree

Exporting the filesystem tree of a docker container can be done by using the docker export command.

If what we have is not a container but a docker image (ubuntu:14.04 in this example), we will have to generate a container from the image first:

$ docker create --name mycontainer ubuntu:14.04

We can now retrieve the content of this container, and then remove it.

$ mkdir mycontainer_fs 
$ cd mycontainer_fs/
$ docker export mycontainer | tar xf -
$ docker rm mycontainer   # not needed anymore

Customization

The OS embedded in official Ubuntu docker images is slightly customized. In particular, starting services is disallowed. We have to revert this:

$ chroot .
$ rm /usr/sbin/policy-rc.d
$ dpkg-divert --remove /sbin/initctl
$ exit	# from chroot

debootstick, kvm, etc.

The chroot environment is now ready to be used by debootstick, and you may follow the usual workflow, starting at step 2.