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I have a Docker image which is a server for a web IDE (Jupyter notebook) for Haskell.

Each time I want to allow the usage of a library in the IDE, I have to go to the Dockerfile and add the install command into it, then rebuild the image.

Another drawback of this, I have to fork the original image on Github, not allowing me to contribute to it.

I was thinking about writing another Dockerfile which pulls the base one with the FROM directive and then RUNs the commands to install the libraries. But, as they are in separate layers, the guest system does not find the Haskell package manager command.

TL;DR: I want to run stack install <library> (stack is like npm or pip, but for Haskell) from the Dockerfile, but I dont want to have a fork of the base image.

How could I solve this problem?

Nick Tchayka
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  • Which base image are you using? What you want to do is fine, but it sounds like the base image doesn't have `stack` installed (or installs it and removes it later), so you'll need to install `stack` in your Dockerfile. – Elton Stoneman Sep 21 '16 at 09:48
  • I'm using gibiansky/ihaskell. I checked the dockerfile and it has it installed explicitly. I also ssh'd into it when running and executed stack with no issues @EltonStoneman – Nick Tchayka Sep 21 '16 at 15:33
  • Yes, it is there in the image. What is the `stack` command you want to run in your Dockerfile? – Elton Stoneman Sep 22 '16 at 06:06
  • `stack install Frames` would be one for example – Nick Tchayka Sep 25 '16 at 12:35

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I was thinking about writing another Dockerfile which pulls the base one with the FROM directive and then RUNs the commands to install the libraries. But, as they are in separate layers, the guest system does not find the Haskell package manager command.

This is indeed the correct way to do this, and it should work. I'm not sure I understand the "layers" problem here - the commands executed by RUN should be running in an intermediate container that contains all of the layers from the base image and the previous RUN commands. (Ignoring the possibility of multi-stage builds, but these were added in 17.05 and did not exist when this question was posted.)

The only scenario I can see where stack might work in the running container but not in the Dockerfile RUN command would be if the $PATH variable isn't set correctly at this point. Check this variable, and make sure RUN is running as the correct user?

Christoph Burschka
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