Is it possible to pass custom environment variables to the docker container?

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Passing Custom Environment Variables to Docker Container

fzngagan asked if it’s possible to pass custom environment variables to a Docker container via a YAML file. They initially tried adding export VAR=VALUE to the custom commands section and VARIABLE: VALUE to the env section, but encountered issues.

Justin suggested using the env: section of the container definition, which fzngagan initially had trouble with due to a multiline value. However, fzngagan eventually got it working by removing the multiline value.

To use multiline values, fzngagan found that wrapping the key in single quotes and adding an extra \ to each \n was necessary. However, featheredtoast suggested a cleaner approach using YAML’s multiline support with the | character.

fzngagan clarified that the key can be pasted as-is with no edits, aside from prefixed spaces. This approach was confirmed by featheredtoast.

In summary, to pass custom environment variables to a Docker container, use the env: section of the container definition, and for multiline values, use YAML’s multiline support with the | character.

1

Some client libraries like GitHub - googleapis/google-auth-library-ruby: Google Auth Library for Ruby · GitHub require the authentication credentials to be set as environment variables. Is it possible to pass them via the yml file.

I tried

  1. Adding export VAR=VALUE to the custom commands section of the yml file.
  2. Adding VARIABLE: VALUE to the env section of the yml.
2

@merefield pointed out to me that its indeed possible.

in the custom commands section do

# adds the variable to .bashrc file
exec: echo 'export VAR=value' >> ~/.bashrc
...
# reloads the file 
exec: source ~/.bashrc

I can confirm that this approach indeed works. :slight_smile:

p.s.
Somehow the source ~/.bashrc doesn’t update the environment. Maybe its being called too early.

Also tried,
- exec: /bin/bash -c "source ~/.bashrc"

3

Can’t you use the env: section of the container definition for this? That should create an environment variable the Rails app can access.

So like

env:
  CUSTOM_ENV: "value"

Otherwise it looks like pups already pipes in env variables on the host, too.

4

That gives me an error related to docker. That would be very intuitive if it worked like that. :slight_smile: Or I’m crazy. I think there’s a rule to accept custom vars starting with DISCOURSE_.

5

I’ll try the env thing once again when I get at my desk tomorrow.

6

So, I was crazy. This works fine. The issue was due to a multiline value. I removed it and the build suceeded. But the question is, how to use multiline values?

7

Yuhoo, I was able to make it work. The issue was that I was using a RSA Private key as an environment variable. This is what needs to be done to make that work.

wrap your key in single quotes '' and add an extra \ with all the \n appearing in the key. i.e. \n would be come \\n.

8

just FYI, there are easier ways of doing that then updating all of the \n directly.

Something like this:

key: |
  ---BEGIN SECRET KEY---
  SHH do not read this is secret
  ---END SECRET KEY---
9

Do you mean pasting the middle part of the key as it is? That would be somewhat more cleaner.

10

I mean that yml has multiline support starting with the | character (and optional variations)

You can then paste the key as-is with no edits (aside from prefixed spaces).

11

I tried a silly thing I added | and an actual new line instead of each \n which didn’t work.