Repo2docker: Support custom environment variables

[choldgraf]

We should let users define environment variables w/ their repositories.

Maybe env.txt ? Each line should have <KEY>=<VAL>?

There are two components to this:

• [x] Make it possible to invoke repo2docker with environment variables (#186 )
• [x] Document the above CLI functionality (#295)
• [ ] Add support to perform this action with a config file (e.g. env.txt)

[yuvipanda]

In general I think we should find whatever heroku does and copy it.

On Jun 27, 2017 10:28 AM, "Chris Holdgraf" [e-mail] wrote:

We should let users define environment variables w/ their repositories.

Maybe env.txt ? Each line should have =?

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[yuvipanda]

Heroku uses a .env file.

[sbinet]

apologies in advance for bumping this issue, but I ran into this issue as well while converting my old Dockerfile-based repo to the new recommanded way (_ie:_ repo2docker)

My repo uses Go and its Jupyterkernel, so I had to install both.
using postBuild and apt.txt worked fine during the docker image creation.

but when actually running the notebook, I also need to have a few Go related environment variables available ($GOPATH and a couple of entries in $PATH)

it would be valuable to just have a simple declarative way to tell the build system what are the variables to be inherited for the notebook.

[choldgraf]

so per @yuvipanda 's note above, and from https://devcenter.heroku.com/articles/heroku-local#look-at-the-contents-of-your-env-file,

we could support a file that was just .env and had a structure like:

S3_KEY=mykey
S3_SECRET=mysecret

and it would get inserted at the beginning of the dockerfile

[choldgraf]

another place where this could be useful: I'm apt-installing some things that get installed to a folder that's not in the typical path. I haven't figured out how to update a path via postBuild so perhaps this could be used for that as well

[rprimet]

Before ruling on a file format, maybe a switch could be added to the repo2docker command, e.g. -e ?

[choldgraf]

I propose that we just go with supporting a file called .env that has {key}={value} pairs, and that will be inserted into the Dockerfile before anything else. It doesn't seem like any other major alternatives have popped up.

[betatim]

I think there are two use cases:

• using repo2docker as a CLI tool I would like to be able to insert AUTH tokens at launch time (like docker run -e)
• add permanent ENV variables in a binderhub use case (eg. connection string for a DB)

So I'd champion a command-line option and some file based solution like .env/binder.yaml.

[choldgraf]

that's a good point @betatim - agreed.

by "I'd champion" are you volunteering a PR? :-)

[rprimet]

I'll submit a PR for the flag :-)

[willingc]

@choldgraf @betatim Should we keep this open or close now that #186 has been merged?

[choldgraf]

I don't think quite yet - that PR hit _part_ of this issue but there are still some extra things to do. I updated the top-level comment with a more specific todo list from my perspective

[rprimet]

@choldgraf What kind of documentation would you like ? I can submit a PR but I'm not sure where as the option is documented in the code and the main doc does not have a relevant section (it simply documents the debug and no-build flags) ?

[choldgraf]

Nothing super long, just a place where the information exists on the web, in case people wonder this to themselves before they download the package. Perhaps a "Can I pass environment variables to repo2docker" the faq or adding a short section covering this in the usage page. Either would be much appreciated!

[yuvipanda]

You can do this with 'start' now that #196 is implemented.