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## About

GitHub Action to set up Docker [Buildx](https://github.com/docker/buildx).

This action will create and boot a builder that can be used in the following steps of your workflow if you're using
[buildx](https://github.com/docker/buildx). By default, the `docker-container` [builder driver](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#driver)
will be used to be able to build multi-platform images and export cache thanks to the [BuildKit](https://github.com/moby/buildkit)
container.

![Screenshot](.github/setup-buildx-action.png)

___

* [Usage](#usage)
  * [Quick start](#quick-start)
  * [With QEMU](#with-qemu)
  * [Install by default](#install-by-default)
  * [BuildKit daemon configuration](#buildkit-daemon-configuration)
    * [Registry mirror](#registry-mirror)
    * [Max parallelism](#max-parallelism)
  * [Standalone mode](#standalone-mode)
* [Customizing](#customizing)
  * [inputs](#inputs)
  * [outputs](#outputs)
  * [environment variables](#environment-variables)
* [Notes](#notes)
  * [BuildKit container logs](#buildkit-container-logs)
* [Keep up-to-date with GitHub Dependabot](#keep-up-to-date-with-github-dependabot)

## Usage

### Quick start

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v2
      -
        name: Set up Docker Buildx
        id: buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Inspect builder
        run: |
          echo "Name:      ${{ steps.buildx.outputs.name }}"
          echo "Endpoint:  ${{ steps.buildx.outputs.endpoint }}"
          echo "Status:    ${{ steps.buildx.outputs.status }}"
          echo "Flags:     ${{ steps.buildx.outputs.flags }}"
          echo "Platforms: ${{ steps.buildx.outputs.platforms }}"
```

### With QEMU

If you want support for more platforms you can use our [setup-qemu](https://github.com/docker/setup-qemu-action) action:

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v2
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        id: buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Available platforms
        run: echo ${{ steps.buildx.outputs.platforms }}
```

### Install by default

If you want set up the `docker build` command as an alias to `docker buildx build`:

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v2
      -
        uses: docker/setup-buildx-action@v2
        id: buildx
        with:
          install: true
      -
        name: Build
        run: |
          docker build . # will run buildx
```

### BuildKit daemon configuration

You can provide a [BuildKit configuration](https://github.com/moby/buildkit/blob/master/docs/buildkitd.toml.md)
to your builder if you're using the [`docker-container` driver](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#driver)
(default) with the `config` or `config-inline` inputs:

#### Registry mirror

You can configure a registry mirror using an inline block directly in your
workflow with the `config-inline` input:

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
        with:
          config-inline: |
            [registry."docker.io"]
              mirrors = ["mirror.gcr.io"]
```

#### Max parallelism

You can limit the parallelism of the BuildKit solver which is particularly
useful for low-powered machines.

You can use the `config-inline` input like the
previous example, or you can use a dedicated BuildKit config file from your
repo if you want with the `config` input:

```toml
# .github/buildkitd.toml
[worker.oci]
  max-parallelism = 4
```

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
        with:
          config: .github/buildkitd.toml
```

### Standalone mode

If you don't have the Docker CLI installed on the GitHub Runner, buildx binary
is invoked directly, instead of calling it as a docker plugin. This can be
useful if you want to use the `kubernetes` driver in your self-hosted runner:

```yaml
name: ci

on:
  push:

jobs:
  buildx:
    runs-on: ubuntu-latest
    steps:
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
        with:
          driver: kubernetes
      -
        name: Build
        run: |
          buildx build .
```

## Customizing

### inputs

Following inputs can be used as `step.with` keys

| Name               | Type    | Description                       |
|--------------------|---------|-----------------------------------|
| `version`          | String  | [buildx](https://github.com/docker/buildx) version. (eg. `v0.3.0`, `latest`, `https://github.com/docker/buildx.git#master`) |
| `driver`           | String  | Sets the [builder driver](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#driver) to be used (default `docker-container`) |
| `driver-opts`      | CSV     | List of additional [driver-specific options](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#driver-opt) (eg. `image=moby/buildkit:master`) |
| `buildkitd-flags`  | String  | [Flags for buildkitd](https://github.com/moby/buildkit/blob/master/docs/buildkitd.toml.md) daemon (since [buildx v0.3.0](https://github.com/docker/buildx/releases/tag/v0.3.0)) |
| `install`          | Bool    | Sets up `docker build` command as an alias to `docker buildx` (default `false`) |
| `use`              | Bool    | Switch to this builder instance (default `true`) |
| `endpoint`         | String  | [Optional address for docker socket](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#description) or context from `docker context ls` |
| `config`¹          | String  | [BuildKit config file](https://github.com/docker/buildx/blob/master/docs/reference/buildx_create.md#config) |
| `config-inline`¹   | String  | Same as `config` but inline |

> * ¹ `config` and `config-inline` are mutually exclusive

> `CSV` type must be a newline-delimited string
> ```yaml
> driver-opts: image=moby/buildkit:master
> ```
> ```yaml
> driver-opts: |
>   image=moby/buildkit:master
>   network=host
> ```

### outputs

Following outputs are available

| Name          | Type    | Description                           |
|---------------|---------|---------------------------------------|
| `name`        | String  | Builder name |
| `driver`      | String  | Builder driver |
| `endpoint`    | String  | Builder node endpoint |
| `status`      | String  | Builder node status |
| `flags`       | String  | Builder node flags (if applicable) |
| `platforms`   | String  | Builder node platforms available (comma separated) |

### environment variables

The following [official docker environment variables](https://docs.docker.com/engine/reference/commandline/cli/#environment-variables) are supported:

| Name            | Type    | Default      | Description                                    |
|-----------------|---------|-------------|-------------------------------------------------|
| `DOCKER_CONFIG` | String  | `~/.docker` | The location of your client configuration files |

## Notes

### BuildKit container logs

To display BuildKit container logs (when `docker-container` driver is used) you have to [enable step debug logging](https://docs.github.com/en/actions/managing-workflow-runs/enabling-debug-logging#enabling-step-debug-logging)
or you can also enable debugging in the [setup-buildx action step](https://github.com/docker/setup-buildx-action):

```yaml
  -
    name: Set up Docker Buildx
    uses: docker/setup-buildx-action@v2
    with:
      buildkitd-flags: --debug
```

Logs will be available at the end of a job:

![BuildKit container logs](.github/buildkit-container-logs.png)

## Keep up-to-date with GitHub Dependabot

Since [Dependabot](https://docs.github.com/en/github/administering-a-repository/keeping-your-actions-up-to-date-with-github-dependabot)
has [native GitHub Actions support](https://docs.github.com/en/github/administering-a-repository/configuration-options-for-dependency-updates#package-ecosystem),
to enable it on your GitHub repo all you need to do is add the `.github/dependabot.yml` file:

```yaml
version: 2
updates:
  # Maintain dependencies for GitHub Actions
  - package-ecosystem: "github-actions"
    directory: "/"
    schedule:
      interval: "daily"
```