Docker: how to modify an existing container

This is a problem I had lots of times, and it is possible that I’m not the only one. Scenario:

1. I create a container;
2. I do some work in the container;
3. I need to connect from outside, but I realize that I didn’t map the port.

Or maybe I did, but I need to map it to another port. Or maybe I want to have a volume.

Docker doesn’t natively allow to remap ports or create volumes if a container is already running. When using Docker on localhost for testing, this sucks.

But don’t cry: you don’t need to create a new container.

All you need to do is:

1. docker stop container bad_container
2. docker commit bad_container good_image
3. docker run --name good_container -d -p ... -v ... good_image

Enjoy!