In this video from DockerCon 2017, Liz Rice demonstrates how to implement a container-like thing in a few lines of Go code. I've attempted the same thing, but using Ruby instead of Go.

Note that I worked on this project as a way of learning about containers and hence my approach may be foolish and the code may contain mistakes. Re-use at your own risk!

• Ruby
• Vagrant
• Virtual Box (or another suitable provider)

vbhost$ vagrant up # may take some time

vbhost$ vagrant ssh
ubuntu@ubuntu-xenial:~$ sudo su - root
root@ubuntu-xenial:~# cd /vagrant
root@ubuntu-xenial:/vagrant# ./container run /bin/bash
run: Running ["/bin/bash"] as PID 15742
child: Running ["/bin/bash"] as PID 15744
grandchild: Running ["/bin/bash"] as PID 1
root@container:/# ps
  PID TTY          TIME CMD
    1 ?        00:00:00 ruby
    4 ?        00:00:00 bash
   11 ?        00:00:00 ps
root@container:/# exit
exit
root@ubuntu-xenial:/vagrant#

See Liz's talk and my commit notes for examples of things to explore in the container.

This has only been tested on Ubuntu 16.04.3 and given that it relies heavily on making native system calls, it's likely not to work on other versions of Linux.

Many thanks to Liz Rice for the inspiration of her talk and for making her source code publicly available.