@Skygod: I don't know how different M1+ is from M2, of which Hosteiner mentioned it works fine. If there is a difference, it would be cool to see it it works on the M1+ as well!
@Holsteiner: The Docker version in this image is probably by far not latest, but will probably work fine, which is good to see!
Performance of Docker? Like charm :-) See this is docker daemon without any containers:
$ ps -p 1277 -o %cpu,%mem,cmd
%CPU %MEM CMD
1.1 2.8 /usr/bin/docker daemon -H fd:// --storage-driver=overlay -D
Let's start 20 webservers (https://hub.docker.com/r/hypriot/rpi-busybox-httpd/), i.e. starting 20 containers, and check again:
%CPU %MEM CMD
6.5 3.4 /usr/bin/docker daemon -H fd:// --storage-driver=overlay -D
Note, that this is just the Docker daemon as "container manager" instance!
For each container, Docker starts 4 processes. Please do not ask me why. Let's rather have a look at CPU and RAM:
With 20 webservers running, CPU usage in total and average is about 4%. Before starting these 20 containers, it was a bit more than 2% in average.
RAM usage is 162 MB. Before starting the 20 containers, it was 46 MB.
So in general, only the Docker daemon is put on top. For containers, Docker's footprint is about the same as if you run apps natively. For this test, I used HypriotOS (http://blog.hypriot.com/) on a Raspberry Pi 2 B.
You also can define how much CPU and RAM a container is allowed to have at max, and also in relation to other containers. Docker offers many options to make sure you are in control about available resources.
And, BTW, with some tweaking, it's possible to start 2500 containers on a single Raspberry Pi with Docker :-) -> https://blog.docker.com/2015/10/raspberry-pi-dockercon-challenge-winner/
@September: I can see that several containers are running, which shows that Docker works well, awesome! Thanks for your feedback! Yeah, we are not sure yet how much work it is, but we at least try to get together...