Date posted: 09 Apr 2021, 0 minutes to read

GitHub Actions Create: Dockerfile symlinks error

I was building a new GitHub Action today with a Dockerfile and got a strange error…

GitHub execution error message

I was using a Dockerfile in a sub directory, but the documentation indicates this is supported. So, what gives? Is it a mix-up of the file path? I’m testing it on Windows and can build the Dockerfile itself just fine 🤔. Tested with a backslash instead of a slash, but still an error:

GitHub execution error message with symlinks

The fix

On a hunch (this has happened before!), I changed the file ending of the Dockerfile from CRLF into LF (created the file on Windows of-course!) and… tada:

Working result with a successful Docker build

For future reference

  1. Check the line endings on your Dockerfile!
  2. You can run an image in your GitHub Action in a subdirectory by using the correct path to it. It needs to be relative to the action.yml file!
# action.yml
name: 'Octogotchi'
description: 'Octogotchi'
branding:
  icon : alert-circle
  color: blue
runs:
  using: 'docker'
  image: 'action/Dockerfile'