Docker support should work using non-FP-generated images (not require entrypoint.sh)

[gregwebs]

It looks like it is impossible to use a custom docker image right now.

➜  backend git:(master) ✗ stack build
exec: "/root/entrypoint.sh": stat /root/entrypoint.sh: no such file or directory
FATA[0000] Error response from daemon: Cannot start container 1b60244790aceffc03b3c0ab59156099e0f55b0730b085273f139a1e3a8a8655: [8] System error: exec: "/root/entrypoint.sh": stat /root/entrypoint.sh: no such file or directory 
➜  backend git:(master) ✗ stack --version
Version 0.1.2.0, Git revision 65246552936b7da4b64b38372feac903d96a8911 (dirty)

From looking at the source code, using my own image must be getting identified as an oldImage, so it then gets a --entrypoint argument.

[borsboom]

I think at this point the oldImage logic can be removed. That said, stack's docker integration isn't going to work well with an image that doesn't have a correct entrypoint that handles the user and directory mapping. If you need a custom image, I recommend deriving it from the fpco/stack-run docker image repository.

[gregwebs]

Where are the Dockerfile's for the fpco images? I cannot find any of them.
Where is the entrypoint script? I would imagine it should be easy to drop that into my images.

[borsboom]

The fpco images aren't built using Dockerfiles, and the current build tool contains some proprietary information and so we can't open source it yet.

In the images, the entrypoint is at /usr/local/sbin/docker-entrypoint, so you can get it using:

docker run -d --name=get-entrypoint fpco/stack-run && \
docker cp get-entrypoint:/usr/local/sbin/docker-entrypoint . && \
docker rm -f get-entrypoint

[gregwebs]

The fpco images aren't built using Dockerfiles, and the current build tool contains some proprietary information and so we can't open source it yet.

Unfortunately I cannot use the fpco images then. Perhaps your can make your build tool capable of generating a Dockerfile

A better way to get the file out (from my point of view at least) is

docker run --entrypoint="/bin/bash" fpco/stack-run -c 'cat /usr/local/sbin/docker-entrypoint' > entrypoint.sh

Thanks for that, I will give it a shot

[borsboom]

I've been looking at this a bit more, and I think it is likely possible to make stack work without the special entrypoint in a slightly degraded form. It would lose the user ID mapping (meaning files it writes would be owned by root) and using the package index and build plan from the image (meaning stack would have to download those).

[gregwebs]

My general workflow is to create a single user for the container and mount things into their home directory. Since I am the first user on my own computer, the uids match up (I know it is hacky, but it always works for my development flow).

For stack, I just need to mount ~/.stack and the project directory.

I think the entrypoint script could be broken up into 2 separate things:

1. a generic entrypoint script that does things such as user id mapping
2. a stack-specific entrypoint that calls the generic entrypoint

I am definitely willing to help make this happen. Let me know.

[gregwebs]

I was able to get things working with my own image by taking the output of stack -v build and modifying it and turning it into a script with "$@" at the end.

I think there is really no reason why stack should not be able to work with the official haskell image.

[borsboom]

I have an approach in mind that will also fully solve #547 (and help #260), where stack will act as its own entrypoint rather than relying on a special entrypoint in the image (which is a historical accident from the bash script we used when we first started using Docker).