Why patch linux kernel on Centos for using Docker.io

Question

I'm trying to shift my applications to a more formalised deployment method like using Docker.io, but as I checked on how it works, it relies on a patched linux kernel. So I'm wondering what such patch is it? What uncertainty it brings if I move my whole architect to go with this patched kernel?

Answer 1

AFAIK, Docker requires:

• a recent enough kernel (>= 3.8) - older versions might misbehave
• cgroups and namespace support enabled
• AUFS support built-in

Ubuntu and Debian default kernel are ok, although Red Hat (and derivative) don't seem to ship AUFS by default.

So what you have to do kernel-wise should sum-up to: build with AUFS (see http://aufs.sourceforge.net/). There seem to exist various tutorials on the web for Centos/Docker, with instructions about the EPEL repository and AUFS support.

More informations about Docker kernel requirements: http://docs.docker.io/en/latest/installation/kernel/

Also note that the AUFS requirement will possibly/probably (?) be dropped in future docker versions, and be replaced by something else.

Finally, about the "uncertainty" this brings to your architecture: I don't think having AUFS support should be a cause for much worry - but you will have to investigate that. About the "uncertainty" that using docker brings, I think it boils down more to the uncertainty that lxc brings. You should probably read about linux containers generally if you want to fully understand the implications (possibly https://help.ubuntu.com/lts/serverguide/lxc.html)

Disclaimer: I'm not a Centos user.