Setup Docker Buildx (Forgejo)

Forgejo's missing docker/setup-buildx-action. Create and bootstrap a docker buildx (BuildKit) builder on a self-hosted Forgejo runner, using the buildx that already ships with the runner's Docker. No buildx binary is downloaded from github.com at runtime.

Part of the Fjord Actions bundle. Pairs with docker-build-action: this action provisions a docker-container builder (the one that supports registry cache export and multi-platform), then the build action uses it.

Why

The default Docker builder (the docker driver) cannot export a BuildKit cache to a registry (--cache-to type=registry) and cannot build multi-platform. For either you need a docker-container builder. docker/setup-buildx-action does that on GitHub but pulls a buildx release from github.com; this action does the same provisioning with the runner's installed buildx, so nothing in the hot path depends on github.com.

Usage

jobs:
  build:
    runs-on: linux-docker        # a runner with real Docker (host mode)
    steps:
      - uses: actions/checkout@v6

      - name: Set up Docker Buildx
        uses: https://rasterhub.com/rasterstate/setup-buildx-action@v1

      - name: Build and push
        uses: https://rasterhub.com/rasterstate/docker-build-action@v1
        with:
          context: .
          file: core/Dockerfile
          push: true
          tags: registry.example.com/app:latest
          cache-from: type=registry,ref=registry.example.com/app:buildcache
          cache-to: type=registry,ref=registry.example.com/app:buildcache,mode=max

Zero-config gives you a bootstrapped docker-container builder set as current (--use), torn down in a post step at job end.

Inputs

Input	Default	Description
driver	docker-container	Builder driver: docker-container, docker, kubernetes, remote.
driver-opts		Driver options key=value, one per line (e.g. image=moby/buildkit:v0.16.0, network=host).
buildkitd-flags		Flags for the buildkitd daemon (e.g. --allow-insecure-entitlement network.host).
buildkitd-config		Path to a BuildKit daemon TOML config.
buildkitd-config-inline		Inline BuildKit TOML; written to a temp file and passed as --config.
endpoint		Optional node endpoint for the builder.
platforms		Fixed platforms for the node, comma separated.
name	auto	Builder name. Required when append is true.
append	false	Append a node to the existing builder named by name.
install	false	Set buildx as the default docker build (docker buildx install). Reverted on cleanup.
use	true	Switch the current builder to the one created here.
cleanup	true	Remove the builder in the post step.
keep-state	false	Keep the BuildKit state volume on teardown (docker buildx rm --keep-state).
version		Informational only; see MIGRATION.md.

Outputs

Output	Description
name	Name of the builder created or selected.
driver	Builder driver.
platforms	Comma-separated platforms available on the builder.
endpoint	Endpoint of the first node.
status	Status of the first node (e.g. running).
nodes	JSON array of nodes (name, endpoint, status, platforms).

Requirements

A runner with a real Docker daemon and the buildx plugin (Docker 19.03+). On the Fjord stack that means a host-mode runner (the job runs on the VM and uses its Docker), not a job-container runner that only has the socket mounted.

Pinning BuildKit

The buildx CLI version is whatever the runner's Docker ships. To pin BuildKit (the thing that actually does the build), set the builder image, pulled from your registry or Docker Hub, never GitHub:

      - uses: https://rasterhub.com/rasterstate/setup-buildx-action@v1
        with:
          driver-opts: image=moby/buildkit:v0.16.0

See MIGRATION.md for the differences from docker/setup-buildx-action.

License

MIT, see LICENSE.