Running emacs in a docker container

Question

I'm using a Mac and want to run emacs in my docker container. Is there a preferred way to solve this? In my flow I get stuc because the DISPLAY/TERM aren't set

> docker exec -it c6a7a76db84c bash > sudo apt-get install emacs ... > oot@c6a7a76db84c:/var/log/apache2# emacs Please set the environment variable DISPLAY or TERM (see `tset'). > oot@c6a7a76db84c:/var/log/apache2# tset tset: unknown terminal type unknown Terminal type? 

What should I use for tset? Or is there a preferred way to run emacs in a docker container?

Answer 1

In order to edit files inside a container, it's generally best to use volumes and the editor on the host, as Bryan suggests. In fact, you should never edit a file that's not in a volume as your changes will be lost when the container is removed.

However, it's quite possible and useful to run editors and even GUI applications inside containers. In order to run the command line version of emacs, all I had to do was:

$ docker run -it debian /bin/bash root@02bd877c1052:/# apt-get update && apt-get install -y emacs23-nox root@02bd877c1052:/# emacs 

I've tested this with boot2docker and docker running natively on Linux. I think your problem was because emacs was trying to launch the X version of emacs, which won't work by default as there isn't an XServer running.

If you want to run a GUI application inside a container, you have a few choices:

• Use VNC or similar
• Use ssh -x to do X forwarding (requires an XServer such as xquartz)
• Mount the xsocket inside the container (again requires an XServer and I'm not sure how it will work with xquartz, also there are some security issues with exposing the xsocket)

Please don't believe that containers shouldn't be used for interactive applications. There are many reasons to do so, including security. The subuser project uses Docker to run interactive applications and goes into detail about why this can be a good idea.

Answer 2

As Adrian Mouat mentioned in his comment, just do:

export TERM=xterm 

and you'll be able to run emacs (note, though, that you'll always have to double-enter C-p to move to previous line, because Docker).