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docker-compose

  • Compose profiles before profiles: two files and a merge

    Note1 min read

    Wanting the mail catcher and phpMyAdmin locally but not in CI, without maintaining two full compose files, is the problem profiles eventually solve. In 2018 the answer is…

  • Compose file version 3, and what swarm changed

    Deep dive10 min read

    v3 exists to be deployable to a scheduler, and that removes things a single-host file relied on. What went, why it had to, and what replaces it.

  • Multi-stage builds cut the image in half

    Deep dive9 min read

    17.05 made the two-Dockerfile trick unnecessary. Named stages, what to copy forward, and why the build cache still rewards the order of instructions.

  • Compose file v3 dropped volumes_from

    Note2 min read

    A version 2 file could share a container’s volumes with volumes_from, which is how the data-container pattern worked. Version 3 removes it, because a scheduler placing containers on…

  • depends_on does not wait for readiness, and never did

    Note1 min read

    depends_on controls start order and nothing else. The database container being started is not the database accepting connections, so the application starts, fails to connect, and exits. Version…

  • Docker for Mac replaced the virtual machine

    Deep dive8 min read

    The shared-folder problem that nearly killed this last year is gone. What changes in the compose file, what the new file sharing costs, and where Linux and Mac…

  • Compose file version 2 moved services under a key

    Note2 min read

    A version 1 compose file is a bare map of service names. Version 2 nests them under services, which looks like churn and is what makes room for…