Dockerfile

A Dockerfile lists the instructions that docker build follows to create an image. Each instruction (FROM, COPY, RUN, USER, CMD...) adds a layer, and Docker caches the layers that did not change.

Key concepts #

• FROM chooses the base image, and several FROM lines create a multi-stage build.
• Build cache: put the instructions that change rarely first.
• .dockerignore keeps files and secrets out of the build context.
• CMD and ENTRYPOINT define what the container runs.
• BuildKit adds cache mounts, secret mounts and multi-platform builds. See BuildKit and buildx.

Learn it #

Dockerfile tutorial.