On the new Cloud9 version you have full root access. We are now providing Ubuntu 14.04 LTS as a Docker container. Feel free to install whatever you want.

Last time I read about Docker and root it was not a good combination. Afaik Docker is not secure (yet).

I hope you take extra precautions to secure Docker containers from each other.

For those interested, Daniel Walsh gave a good overview of the biggest issues at dockercon: https://www.youtube.com/watch?v=zWGFqMuEHdw

Ops, that was a mistake on our end, just fixed for everyone. Sorry!