rules_docker (αlpha)

These are repository rules for building deterministic base docker images with bazel. Bazel provides fantastic support for this with the docker_build rule. This function removes timestamps and other non-deterministic data in order to repeatably build docker images based on content alone.

In practice however, using the docker_build rule is challenging as one is expected to build images based on vendoring of layers via deb archives. This makes it hard to use distros that use different packaging systems such as Alpine Linux.

The idea with these rules is that you construct a root filesystem based on a Dockerfile instructions and then layer on your build artifacts.

Rule	Description
docker_rootfs	Repository rule that provides a rootfs from the docker export command.
docker_rootfs_http_file	Repository rule that provides a rootfs from a file fetched via http.
docker_rootfs_github_repository	Repository rule that provides a rootfs from a github repository.
docker_build	Package macro that calls the @bazel_tools//tools/docker/docker_build.bzl rule with an alternative incremental_load.sh.tpl template file. See #1651

You must have docker running, bazel won't download/install it for you at the moment. Requires bazel 0.3.1 or HEAD is required (fails with 0.3.0).

Step 1: Add rules_docker to your workspace

git_repository(
    name = "org_pubref_rules_docker",
    commit = "COMMIT_ID",
    remote = "https://github.com/pubref/rules_docker.git",
)
load("@org_pubref_rules_docker//docker:rules.bzl",
     "docker_rootfs",
     # "docker_rootfs_http_file",
     # "docker_rootfs_github_repository",
)

Step 2: Add docker_rootfs rules to your workspace as needed

Example repository rule to generate a rootfs.tar from the busybox image. The image becomes available at @busybox//:base.

docker_rootfs(
    name = "busybox",
    dockerfile_content = "FROM busybox",
)

Step 3: Use these as base inputs for subsequent layers.

load("@org_pubref_rules_docker//docker:rules.bzl", "docker_build")

docker_build(
    name = "foo",
    base = "@busybox//:base",
    ...
)

Step 4: Load/run it in docker

Generate and run a deterministic docker image with:

$ bazel run :foo gcr.io/example:busybox
$ docker run -it gcr.io/example:busybox sh

---

Provided BUILD Targets

One can also directly use the targets provided by this workspace:

$  bazel query //... --output label_kind
docker_build  rule  //alpine:3_4
docker_build  rule  //alpine:alpine
docker_build  rule  //alpine:edge
docker_build  rule  //alpine:go
docker_build  rule  //alpine:java8
docker_build  rule  //debian:wheezy
docker_build  rule  //docker:scratch
docker_build  rule  //ubuntu:trusty

Additional Links

• Blog Post: https://bazel.io/blog/2015/07/28/docker_build.html
• Source: https://github.com/bazelbuild/bazel/blob/master/tools/build_defs/docker/docker.bzl
• Issue #1058 for docker_pull rule: bazelbuild/bazel#1058