hadolint

packaged by Chainguard

Chainguard Container for hadolint

Dockerfile linter, validate inline bash, written in Haskell

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/hadolint:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

Chainguard's hadolint image is comparable to the upstream hadolint/hadolint image and can be used as a drop-in replacement. The upstream image runs as root, while the Chainguard image runs as non-root UID 65532. Any files mounted into the Chainguard image must be readable by that user.

Getting Started

Create a sample Dockerfile:

cat > Dockerfile <<'EOF'
FROM alpine
RUN echo "hello"
CMD ["true"]
EOF

Lint it by piping it to the container over stdin:

docker run --rm -i cgr.dev/ORGANIZATION/hadolint:latest hadolint - < Dockerfile

Hadolint reports that the base image does not have a tag:

-:1 DL3006 warning: Always tag the version of an image explicitly

Add a version tag to the FROM instruction:

cat > Dockerfile <<'EOF'
FROM alpine:3.20
RUN echo "hello"
CMD ["true"]
EOF

Lint the updated Dockerfile:

docker run --rm -i cgr.dev/ORGANIZATION/hadolint:latest hadolint - < Dockerfile

Hadolint prints nothing and exits successfully when it finds no issues.

To lint a mounted file instead, include hadolint and the file path after the image reference:

docker run --rm \
  -v "$PWD/Dockerfile:/Dockerfile:ro" \
  cgr.dev/ORGANIZATION/hadolint:latest hadolint /Dockerfile

Configuration

Hadolint accepts command-line options, environment variables, and YAML configuration files. For example, a CI job can emit machine-readable output and fail only for findings at warning severity or higher. Create a .hadolint.yaml file:

cat > .hadolint.yaml <<'EOF'
failure-threshold: warning
format: json
no-color: true
EOF

Mount the configuration file and lint the Dockerfile:

docker run --rm -i \
  -v "$PWD/.hadolint.yaml:/.hadolint.yaml:ro" \
  cgr.dev/ORGANIZATION/hadolint:latest \
  hadolint --config /.hadolint.yaml - < Dockerfile

For the sample Dockerfile, Hadolint returns an empty JSON array:

[]

Adjust the failure threshold to match your policy. Refer to the Hadolint configuration documentation for the complete set of options and environment variables.

Documentation and Resources

• Hadolint GitHub repository
• Hadolint rules reference

What are Chainguard Containers?

Chainguard's free tier of Starter container images are built with Wolfi, our minimal Linux undistro.

All other Chainguard Containers are built with Chainguard OS, Chainguard's minimal Linux operating system designed to produce container images that meet the requirements of a more secure software supply chain.

The main features of Chainguard Containers include:

• Minimal design, without unnecessary software bloat
• Daily builds to ensure container images are up-to-date with available security patches
• High quality build-time SBOMs attesting to the provenance of all artifacts within the image
• Verifiable signatures provided by Sigstore
• Reproducible builds with Cosign and apko (read more about reproducibility)

For cases where you need container images with shells and package managers to build or debug, most Chainguard Containers come paired with a development, or -dev, variant.

In all other cases, including Chainguard Containers tagged as :latest or with a specific version number, the container images include only an open-source application and its runtime dependencies. These minimal container images typically do not contain a shell or package manager.

Although the -dev container image variants have similar security features as their more minimal versions, they include additional software that is typically not necessary in production environments. We recommend using multi-stage builds to copy artifacts from the -dev variant into a more minimal production image.

Need additional packages?

To improve security, Chainguard Containers include only essential dependencies. Need more packages? Chainguard customers can use Custom Assembly to add packages, either through the Console, chainctl, or API.

To use Custom Assembly in the Chainguard Console: navigate to the image you'd like to customize in your Organization's list of images, and click on the Customize image button at the top of the page.

Learn More

Refer to our Chainguard Containers documentation on Chainguard Academy. Chainguard also offers VMs and Libraries — contact us for access.

Trademarks

This software listing is packaged by Chainguard. The trademarks set forth in this offering are owned by their respective companies, and use of them does not imply any affiliation, sponsorship, or endorsement by such companies.