docker-stacks/docs/contributing/lint.md

Lint

In order to enforce some rules linters are used in this project. Linters can be run either during the development phase (by the developer) and during integration phase (by GitHub Actions). To integrate and enforce this process in the project lifecycle we are using git hooks through pre-commit.

Using pre-commit hooks

Pre-commit hook installation

pre-commit is a Python package that needs to be installed. This can be achieved by using the generic task used to install all Python development dependencies.

# Install all development dependencies for the project
make dev-env
# It can also be installed directly
pip install pre-commit

Then the git hooks scripts configured for the project in .pre-commit-config.yaml need to be installed in the local git repository.

make pre-commit-install

Run

Now pre-commit (and so configured hooks) will run automatically on git commit on each changed file. However it is also possible to trigger it against all files.

Hadolint pre-commit uses docker to run, so docker should be running while running this command.

make pre-commit-all

Image Lint

To comply with Docker best practices, we are using the Hadolint tool to analyse each Dockerfile.

Ignoring Rules

Sometimes it is necessary to ignore some rules. The following rules are ignored by default for all images in the .hadolint.yaml file.

• DL3006: We use a specific policy to manage image tags.
  • base-notebook FROM clause is fixed but based on an argument (ARG).
  • Building downstream images from (FROM) the latest is done on purpose.
• DL3008: System packages are always updated (apt-get) to the latest version.

For other rules, the preferred way to do it is to flag ignored rules in the Dockerfile.

It is also possible to ignore rules by using a special comment directly above the Dockerfile instruction you want to make an exception for. Ignore rule comments look like # hadolint ignore=DL3001,SC1081. For example:

FROM ubuntu

# hadolint ignore=DL3003,SC1035
RUN cd /tmp && echo "hello!"