Dlock allows deterministic builds of Docker images by locking base images and making upgrades explicit.
Think of package-lock.json, Pipfile.lock, or composer.lock for Docker.
Dlock is hosted at GitHub and it can be installed from PyPI.
Imagine that you have a Dockerfile for an application that runs Python 3.8:
FROM python:3.8-slim-busterAn image built using your Dockerfile will use the latest Python 3.8 on the latest Debian Buster as a base image. It means that when you rebuild the image, you will get the most recent fixes from both Python and Debian.
It is desired to promptly incorporate all security patches, but your build process is unpredictable:
- You have no control when your base images will be upgraded.
- You do not see a history of dependency versions used.
- You can unintentionally downgrade if you forget
docker pull. - It is difficult to downgrade when a problem appears.
- You still have no guarantee that your images will be rebuilt when a new base image is published.
This is where Dlock can help. It locks your base image by adding a SHA-256 digest to it:
$ dlock
Dockerfile: one base image locked
Dockerfile: changes saved
FROM python:3.8-slim-buster@sha256:0944c626f71b2f44ed45c13761f3cb97d75566261ade2b2d34f6ce2987dacbcbThe above syntax is understood by Docker. Docker ignores a tag when a digest is specified.
You should commit the updated Dockerfile. From now on, when you build your image, you can be sure that the locked version will be used.
Locking your dependencies does not prevent upgrades, it makes them explicit. When a new base image is published, you can upgrade using Dlock:
$ dlock --upgrade
Dockerfile: one base image upgraded
Dockerfile: changes saved
FROM python:3.8-slim-buster@sha256:b462bcd5273cc6e4afc167db410d1e113a3174c1cab6ebe946efc1d1f03a9397Now you can commit your Dockerfile again, and all future builds will use the new base image version.
With the described approach, history of all your dependencies is tracked in a version control system, so you can easily return to previous versions if necessary. And because the dependencies are not upgraded randomly, it forces to you setup a proper policy of regular upgrades.
Dlock requires Python 3.7 or newer and can be installed using pip:
pip install dlockSee the command help for usage:
dlock --help- Code is formatted using Black and isort.
- Style is enforced using flake8.
- Typing is checked using Mypy.
- Tests are run using pytest.
tox is configured to run all of the above tools.
toxTo run dev tools individually, Dlock can be installed locally with dev dependencies.
pip install --editable .[dev]black src/ tests/ && isort src/ tests/
flake8
mypy
pytest- ...
- Add a
--versionargument. - Lock dependencies referenced in
COPY --from=... - Accept flags (for example
--platform) in FROM instructions. - Refactor Dockerfile parsing to preserve more formatting.
- Initial release
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