Docker on embedded systems, why not?
There was a project thrown my way recently that involves the orchestration of several (Linux capable) embedded devices, deploying software to them, and allowing for the applications to be updated when the code base updates in a git repo.
The initial thought was to make a standard image for each device, and I set out, attempting to install docker on an UDOO Quad and an Intel Edison to start, but without any success up to this point.
My thinking is that it seems to be a good idea to install Docker on embedded devices--but if that's the case, surely it would have been ported by now. The only group out there that seems to be making these efforts is Resin.io.
Is there something I'm missing, or is there a clear reason why Docker doesn't make sense on embedded devices? If there isn't a reason, and it does make sense to run Docker on embedded systems, is there something I've overlooked out there: are there any sources of discussion on porting, or how-to's that cover this?
Answer
I have considered running docker on embedded devices (a mips system), but didn't go that way. There are some problems with it, in my humble view:
Docker is implemented in Golang. There is currently no available tool chain for mips to compile go. You will need to create the tool chain yourself using gcc-go.
The size of docker is larger than lxc. In a desktop computer this is not a problem, but the embedded device has limited flash storage.
Docker uses some quite up-to-date feature of linux kernel. Sometimes the kernel version on embedded devices are not so new and back-port is needed to make it work.
The docker image has to be built on the same architecture as the run time environment. It means that if you want to run a docker container on Raspberry Pi, the docker image has to be built on an ARM-architecture system. QEMU can be used to build docker image in the cloud, but it doesn't support all CPU architectures used in embedded system. (for example, it currently doesn't support MIPS)
In the end, lxc was chosen for the specific task of running a container on embedded device. It has limited features compared to docker, but currently it suits the requirement of the project.
As of year 2019, I would like to update this answer since I did port docker to embedded system with ARM cpu. With the price of flash usage, memory usage, by using docker you will have container management, image management, and many ready to run images from docker hub. So the decision is a balance between cost and features.