I was building a new GitHub Action today with a Dockerfile and got a strange error… `unable to prepare context: path “/action” not found.

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: unable to prepare context: unable to evaluate symlinks in Dockerfile path: lstat /path/to/Dockerfile

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… 🎉.

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'