wp-docker-buildx/DOCS.md

Use the Docker plugin to build and push Docker images to a registry. The following parameters are used to configure this plugin:

• registry - authenticates to this registry
• username - authenticates with this username
• password - authenticates with this password
• email - authenticates with this email
• repo - repository name for the image
• tag - repository tag for the image
• insecure - enable insecure communication to this registry
• mirror - use a mirror registry instead of pulling images directly from the central Hub
• storage_driver - use aufs, devicemapper, btrfs or overlay driver
• save - save image layers to the specified tar file (see docker save)
  • file - absolute / relative destination path
  • tags - cherry-pick tags to save (optional)
• load - restore image layers from the specified tar file

The following is a sample Docker configuration in your .drone.yml file:

publish:
  docker:
    username: kevinbacon
    password: $$DOCKER_PASSWORD
    email: kevin.bacon@mail.com
    repo: foo/bar
    tag: latest
    file: Dockerfile
    insecure: false

You may want to dynamically tag your image. Use the $$BRANCH, $$COMMIT and $$BUILD_NUMBER variables to tag your image with the branch, commit sha or build number:

publish:
  docker:
    username: kevinbacon
    password: $$DOCKER_PASSWORD
    email: kevin.bacon@mail.com
    repo: foo/bar
    tag: $$BRANCH

Or you may prefer to build an image with multiple tags:

publish:
  docker:
    username: kevinbacon
    password: $$DOCKER_PASSWORD
    email: kevin.bacon@mail.com
    repo: foo/bar
    tag:
      - latest
      - "1.0.1"
      - "1.0"

Note that in the above example we quote the version numbers. If the yaml parser interprets the value as a number it will cause a parsing error.

Layer Caching

The Drone build environment is, by default, ephemeral meaning that you layers are not saved between builds. The below example combines Drone's caching feature and Docker's save and load capabilities to cache and restore image layers between builds:

publish:
  docker:
    username: kevinbacon
    password: $$DOCKER_PASSWORD
    email: kevin.bacon@mail.com
    repo: foo/bar
    tag:
      - latest
      - "1.0.1"
    load: docker/image.tar
    save:
      file: docker/image.tar
      tags: latest

cache:
  mount:
    - docker/image.tar

In some cases caching will greatly improve build performance, however, the tradeoff is that caching Docker image layers may consume very large amounts of disk space.

Troubleshooting

For detailed output you can set the DOCKER_LAUNCH_DEBUG environment variable in your plugin configuration. This starts Docker with verbose logging enabled.

publish:
  docker:
    environment:
      - DOCKER_LAUNCH_DEBUG=true

Known Issues

There are known issues when attempting to run this plugin on CentOS, RedHat, and Linux installations that do not have a supported storage driver installed. You can check by running docker info | grep 'Storage Driver:' on your host machine. If the storage driver is not aufs or overlay you will need to re-configure your host machine.

This error occurs when trying to use the default aufs storage Driver but aufs is not installed:

level=fatal msg="Error starting daemon: error initializing graphdriver: driver not supported

This error occurs when trying to use the overlay storage Driver but overlay is not installed:

level=error msg="'overlay' not found as a supported filesystem on this host.
Please ensure kernel is new enough and has overlay support loaded."
level=fatal msg="Error starting daemon: error initializing graphdriver: driver not supported"

This error occurs when using CentOS or RedHat which default to the devicemapper storage driver:

level=error msg="There are no more loopback devices available."
level=fatal msg="Error starting daemon: error initializing graphdriver: loopback mounting failed"
Cannot connect to the Docker daemon. Is 'docker -d' running on this host?

The above issue can be resolved by setting storage_driver: vfs in the .drone.yml file. This may work, but will have very poor performance as discussed here.