Lightweight containers with Docker

readme.md

I was curious to find out if there was a way of maintaing docker's great user experience, while being able to enjoy the simplicity of cgroups on their own.

This has it's benefits, as there's no need to transfer any data in an image that isn't required for your individual service. You can also more easily share packages and installations with the host operating system.

Launch a container with all of the important host stuff mounted

$ sudo docker run -d \
    -v /bin:/bin:ro \
    -v /dev:/dev:ro \
    -v /home:/home:ro \
    -v /lib:/lib:ro \
    -v /lib64:/lib64:ro \
    -v /run:/run:ro \
    -v /sbin:/sbin:ro \
    -v /srv:/srv:ro \
    -v /sys:/sys:ro \
    -v /var:/var:ro \
    --cidfile=/tmp/host-container \
    scratch \
    /bin/bash

Launch two more containers and write different values to the same path

$ export CONTAINER_A=$(sudo docker run -d --volumes-from `cat /tmp/host-container` -t -i scratch /bin/bash -c "mkdir /etc; echo 1 > /etc/foo; cat /etc/foo; sleep 60")
$ export CONTAINER_B=$(sudo docker run -d --volumes-from `cat /tmp/host-container` -t -i scratch /bin/bash -c "mkdir /etc; echo 2 > /etc/foo; cat /etc/foo; sleep 60")

Read the relevent files

$ sudo cat /var/lib/docker/aufs/mnt/$CONTAINER_A/etc/foo
1
$ sudo cat /var/lib/docker/aufs/mnt/$CONTAINER_B/etc/foo
2