Interpolation

The manifest supports ${VAR} interpolation: each ${VAR} is replaced with the value of VAR from the environment when Dockform loads the manifest.

Only the plain ${VAR} form is supported. Compose's extras such as ${VAR:-default} or ${VAR:?error} don't work in the manifest (they still work inside your compose files, which Compose interpolates itself). If a variable isn't set, it becomes an empty string and Dockform prints a warning naming it. Run dockform manifest render to see the manifest after interpolation.

Example

# export a variable
$ export AGE_KEY_FILE=~/.config/sops/age/keys.txt

identifier: my_project

contexts:
  default: {}

sops:
  age:
    key_file: ${AGE_KEY_FILE}

identifier: my_project

contexts:
  default: {}

sops:
  age:
    key_file: ~/.config/sops/age/keys.txt

This is especially useful when handling secrets and sensitive values outside of Dockform, such as in GitHub Actions or other CI/CD systems. By interpolating environment variables, you can keep credentials and tokens out of the manifest file while still making them available at runtime.

E.g.:

stacks:
  default/website:
    environment:
      inline:
        - API_KEY=${GITHUB_TOKEN}