Can't get docker running on Cloud9 IDE

Update: The answer below applies to c9.io, not AWS Cloud9. AWS Cloud9 allows you to run docker as you would normally on whatever backing you're using for the environment, whether EC2 or another VM provider.

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Installing Docker inside a Cloud9 workspace will not work because C9 workspaces run on Docker. Running Docker inside Docker would require special permissions and is, therefore, advised against by those who know best for security reasons.

That being said, you can use Docker from an SSH workspace, which allows you to connect Cloud9 to your own server. Since that workspace isn't running in Docker (on Cloud9's servers) you can do whatever you want with it (including run Docker).

I am suspicious about the line apt-get install docker as this is some other docker. You might want to try docker.io or lxc-docker as per http://docs.docker.com/installation/ubuntulinux/

Cloud9 IDE (c9.io) does not support Docker since the environment itself is using Docker. They don't want users getting too close to the root Docker level environment. Here's their info on Docker and other software they do not support: Cloud9 Software they do not support list. I was able to install Docker on c9.io but it was throwing errors when trying to use the Docker stable repo install method; which led me here.

Interestingly the AWS Hosted version of cloud 9 does allow for deeper usage of Docker. Unfortunately, this is a seperate cost and interface to users through AWS... perhaps I'll switch all together? Here's that info on AWS Cloud9 supporting Docker and a link to AWS landing page for cloud9.