It is some initial thoughts and experiences with using Docker for about a week. Specifically I was getting JIRA up and running in Docker on Rackspace for my own use (and it directly receives crash reports from some of my iOS apps). I also used it on my home server to set up a build environment for a JIRA plugin.
Update - Rackspace Cloud Servers Advice
Rackspace Cloud Servers are currently configured with no swapfile. I strongly recommend following the instructions to create a swapfile otherwise once you hit the limit of your server memory it will kill a process (probably your biggest which could well be Java).
General Docker Thoughts
Docker is nice, new containers spin up quickly, the documentation is OK. It is still pre-1.0 so moving fast and much of the online articles about it are out of date already. This isn’t really the first place you should look for information so I’m generally not going to explain syntax or concepts except to give my understanding of the difference between images and containers.