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Hadolint

Hadolint analyzes Dockerfiles and reports common mistakes, unsafe patterns, portability issues, and maintainability problems.

It combines Dockerfile-specific rules with ShellCheck analysis for shell commands used inside RUN instructions.

Installation

Hadolint is installed through Homebrew:

brew install hadolint

It is part of the curated Homebrew environment; see Homebrew setup to install everything at once.

Verify the installation

Check that Hadolint is available:

hadolint --version

Analyze a Dockerfile

Run Hadolint against a Dockerfile with:

hadolint Dockerfile

Hadolint reporting Dockerfile warnings and a fixed passing run

A Dockerfile with a different name can also be analyzed:

hadolint path/to/Dockerfile.dev

To analyze all Dockerfiles tracked by Git:

git ls-files -z \
  | grep -zE '(^|/)(Dockerfile|Dockerfile\.[^/]+)$' \
  | xargs -0 -r hadolint

Findings

Hadolint findings include a rule identifier such as DL3008 or SC2086.

The DL prefix identifies Dockerfile-specific rules.

The SC prefix identifies ShellCheck rules applied to shell commands inside Dockerfile instructions.

Warnings should normally be corrected instead of ignored.

Targeted exclusions

A specific rule can be ignored for the following instruction:

# hadolint ignore=DL3008
RUN apt-get update && apt-get install -y curl

Exclusions should remain narrow and should only be added when the rule is not appropriate for the specific case.

Global exclusions should be avoided because they can hide future problems.

Configuration

Hadolint can be configured with a .hadolint.yaml file at the repository root.

A configuration file should only be added when the project has concrete requirements that cannot be handled cleanly through the default rules.

The default configuration is preferred until such requirements appear.

Pre-commit integration

Hadolint should eventually be integrated into pre-commit when Dockerfiles are present in the repository.

Homebrew manages the executable, while pre-commit will define which Dockerfiles are analyzed and when the checks run.

Until then, validation can be executed manually with:

hadolint Dockerfile

Rollback

Remove Hadolint with:

brew uninstall hadolint

Then remove its entry from profiles/full/Brewfile.

Any related pre-commit hook or Hadolint configuration must also be removed separately.

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