Properly document how to launch a shell in an image, not just a running container

[gdevenyi]

The documentation lists how to properly use docker exec however it doesn't list how to get a shell in an image.

[wholtz]

Hi @gdevenyi .

I'm not completely sure I understand the request. Are you looking for documentation of this:

docker exec -it <container> /bin/bash

or something else?

[gdevenyi]

Are you looking for documentation of this:

No, I'm looking for documentation on how to get a shell in a non-running container (aka an image), where the default entrypoint has been overridden (ENTRYPOINT ["/usr/local/bin/_entrypoint.sh", "anothercommand"]), such that I get the proper container environment.

After much experimenting and reading the existing dockerfile, I think this is what I need to override:

$ docker run -it --entrypoint /usr/local/bin/_entrypoint.sh <mycontainerimage> /bin/bash

[wholtz]

Yes, if you set a new ENTRYPOINT in a derived image and then you want to get back to the old ENTRYPOINT you can specify the old ENTRYPOINT on the command line:

$ docker run -it --entrypoint /usr/local/bin/_entrypoint.sh <mycontainerimage> /bin/bash

and if you are still using the default (or root) user you can even get away with:

$ docker run -it --entrypoint /bin/bash <mycontainerimage>

As the .bashrc for that user will activate the environment.

I will think about how this would best fit into the documentation. PRs are welcome of course....