docker-build-push/README.md

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## About

GitHub Action to build and push Docker images with [Buildx](https://github.com/docker/buildx)
with full support of the features provided by [Moby BuildKit](https://github.com/moby/buildkit)
builder toolkit. This includes multi-platform build, secrets, remote cache, etc.
and different builder deployment/namespacing options.

![Screenshot](.github/build-push-action.png)

___

* [Usage](#usage)
  * [Git context](#git-context)
  * [Path context](#path-context)
* [Examples](#examples)
* [Customizing](#customizing)
  * [inputs](#inputs)
  * [outputs](#outputs)
* [Troubleshooting](#troubleshooting)
* [Contributing](#contributing)

## Usage

In the examples below we are also using 3 other actions:

* [`setup-buildx`](https://github.com/docker/setup-buildx-action) action will
  create and boot a builder using by default the [`docker-container` driver](https://docs.docker.com/build/building/drivers/docker-container/).
  This is **not required but recommended** using it to be able to build
  multi-platform images, export cache, etc.
* [`setup-qemu`](https://github.com/docker/setup-qemu-action) action can be
  useful if you want to add emulation support with QEMU to be able to build
  against more platforms. 
* [`login`](https://github.com/docker/login-action) action will take care to
  log in against a Docker registry.

### Git context

By default, this action uses the [Git context](https://docs.docker.com/engine/reference/commandline/build/#git-repositories),
so you don't need to use the [`actions/checkout`](https://github.com/actions/checkout/)
action to check out the repository as this will be done directly by [BuildKit](https://github.com/moby/buildkit).

The git reference will be based on the [event that triggered your workflow](https://docs.github.com/en/actions/using-workflows/events-that-trigger-workflows)
and will result in the following context: `https://github.com/<owner>/<repo>.git#<ref>`.

```yaml
name: ci

on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push
        uses: docker/build-push-action@v3
        with:
          push: true
          tags: user/app:latest
```

Be careful because **any file mutation in the steps that precede the build step
will be ignored, including processing of the `.dockerignore` file** since
the context is based on the Git reference. However, you can use the
[Path context](#path-context) using the [`context` input](#inputs) alongside
the [`actions/checkout`](https://github.com/actions/checkout/) action to remove
this restriction.

Default Git context can also be provided using the [Handlebars template](https://handlebarsjs.com/guide/)
expression `{{defaultContext}}`. Here we can use it to provide a subdirectory
to the default Git context:

```yaml
      -
        # Setting up Docker Buildx with docker-container driver is required
        # at the moment to be able to use a subdirectory with Git context
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Build and push
        uses: docker/build-push-action@v3
        with:
          context: "{{defaultContext}}:mysubdir"
          push: true
          tags: user/app:latest
```

> **Warning**
>
> Subdirectory for Git context is available from [BuildKit v0.9.0](https://github.com/moby/buildkit/releases/tag/v0.9.0).
> If you're using the `docker` builder (default if `setup-buildx-action` not used),
> then BuildKit in Docker Engine will be used. As Docker Engine < v22.x.x embeds
> Buildkit 0.8.2 at the moment, it does not support this feature. It's therefore
> required to use the `setup-buildx-action` at the moment.

Building from the current repository automatically uses the [GitHub Token](https://docs.github.com/en/actions/security-guides/automatic-token-authentication),
so it does not need to be passed. If you want to authenticate against another
private repository, you have to use a [secret](https://docs.docker.com/build/ci/github-actions/examples/#secrets)
named `GIT_AUTH_TOKEN` to be able to authenticate against it with Buildx:

```yaml
      -
        name: Build and push
        uses: docker/build-push-action@v3
        with:
          push: true
          tags: user/app:latest
          secrets: |
            GIT_AUTH_TOKEN=${{ secrets.MYTOKEN }}
```

### Path context

```yaml
name: ci

on:
  push:
    branches:
      - 'main'

jobs:
  docker:
    runs-on: ubuntu-latest
    steps:
      -
        name: Checkout
        uses: actions/checkout@v3
      -
        name: Set up QEMU
        uses: docker/setup-qemu-action@v2
      -
        name: Set up Docker Buildx
        uses: docker/setup-buildx-action@v2
      -
        name: Login to Docker Hub
        uses: docker/login-action@v2
        with:
          username: ${{ secrets.DOCKERHUB_USERNAME }}
          password: ${{ secrets.DOCKERHUB_TOKEN }}
      -
        name: Build and push
        uses: docker/build-push-action@v3
        with:
          context: .
          push: true
          tags: user/app:latest
```

## Examples

See https://docs.docker.com/build/ci/github-actions/examples/.

## Customizing

### inputs

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

> `List` type is a newline-delimited string
> ```yaml
> cache-from: |
>   user/app:cache
>   type=local,src=path/to/dir
> ```

> `CSV` type is a comma-delimited string
> ```yaml
> tags: name/app:latest,name/app:1.0.0
> ```

| Name               | Type        | Description                                                                                                                                                                       |
|--------------------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| `add-hosts`        | List/CSV    | List of [customs host-to-IP mapping](https://docs.docker.com/engine/reference/commandline/build/#add-entries-to-container-hosts-file---add-host) (e.g., `docker:10.180.0.1`)      |
| `allow`            | List/CSV    | List of [extra privileged entitlement](https://docs.docker.com/engine/reference/commandline/buildx_build/#allow) (e.g., `network.host,security.insecure`)                         |
| `attests`          | List        | List of [attestation](https://docs.docker.com/build/attestations/) parameters (e.g., `type=sbom,generator=image`)                                                                 | 
| `builder`          | String      | Builder instance (see [setup-buildx](https://github.com/docker/setup-buildx-action) action)                                                                                       |
| `build-args`       | List        | List of [build-time variables](https://docs.docker.com/engine/reference/commandline/buildx_build/#build-arg)                                                                      |
| `build-contexts`   | List        | List of additional [build contexts](https://docs.docker.com/engine/reference/commandline/buildx_build/#build-context) (e.g., `name=path`)                                         |
| `cache-from`       | List        | List of [external cache sources](https://docs.docker.com/engine/reference/commandline/buildx_build/#cache-from) (e.g., `type=local,src=path/to/dir`)                              |
| `cache-to`         | List        | List of [cache export destinations](https://docs.docker.com/engine/reference/commandline/buildx_build/#cache-to) (e.g., `type=local,dest=path/to/dir`)                            |
| `cgroup-parent`    | String      | Optional [parent cgroup](https://docs.docker.com/engine/reference/commandline/build/#use-a-custom-parent-cgroup---cgroup-parent) for the container used in the build              |
| `context`          | String      | Build's context is the set of files located in the specified [`PATH` or `URL`](https://docs.docker.com/engine/reference/commandline/build/) (default [Git context](#git-context)) |
| `file`             | String      | Path to the Dockerfile. (default `{context}/Dockerfile`)                                                                                                                          |
| `labels`           | List        | List of metadata for an image                                                                                                                                                     |
| `load`             | Bool        | [Load](https://docs.docker.com/engine/reference/commandline/buildx_build/#load) is a shorthand for `--output=type=docker` (default `false`)                                       |
| `network`          | String      | Set the networking mode for the `RUN` instructions during build                                                                                                                   |
| `no-cache`         | Bool        | Do not use cache when building the image (default `false`)                                                                                                                        |
| `no-cache-filters` | List/CSV    | Do not cache specified stages                                                                                                                                                     |
| `outputs`¹         | List        | List of [output destinations](https://docs.docker.com/engine/reference/commandline/buildx_build/#output) (format: `type=local,dest=path`)                                         |
| `platforms`        | List/CSV    | List of [target platforms](https://docs.docker.com/engine/reference/commandline/buildx_build/#platform) for build                                                                 |
| `provenance`       | Bool/String | Generate [provenance](https://docs.docker.com/build/attestations/slsa-provenance/) attestation for the build (shorthand for `--attest=type=provenance`)                           |
| `pull`             | Bool        | Always attempt to pull all referenced images (default `false`)                                                                                                                    |
| `push`             | Bool        | [Push](https://docs.docker.com/engine/reference/commandline/buildx_build/#push) is a shorthand for `--output=type=registry` (default `false`)                                     |
| `sbom`             | Bool/String | Generate [SBOM](https://docs.docker.com/build/attestations/sbom/) attestation for the build (shorthand for `--attest=type=sbom`)                                                  |
| `secrets`          | List        | List of [secrets](https://docs.docker.com/engine/reference/commandline/buildx_build/#secret) to expose to the build (e.g., `key=string`, `GIT_AUTH_TOKEN=mytoken`)                |
| `secret-files`     | List        | List of [secret files](https://docs.docker.com/engine/reference/commandline/buildx_build/#secret) to expose to the build (e.g., `key=filename`, `MY_SECRET=./secret.txt`)         |
| `shm-size`         | String      | Size of [`/dev/shm`](https://docs.docker.com/engine/reference/commandline/buildx_build/#shm-size) (e.g., `2g`)                                                                    |
| `ssh`              | List        | List of [SSH agent socket or keys](https://docs.docker.com/engine/reference/commandline/buildx_build/#ssh) to expose to the build                                                 |
| `tags`             | List/CSV    | List of tags                                                                                                                                                                      |
| `target`           | String      | Sets the target stage to build                                                                                                                                                    |
| `ulimit`           | List        | [Ulimit](https://docs.docker.com/engine/reference/commandline/buildx_build/#ulimit) options (e.g., `nofile=1024:1024`)                                                            |
| `github-token`     | String      | GitHub Token used to authenticate against a repository for [Git context](#git-context) (default `${{ github.token }}`)                                                            |

> **Note**
>
> * ¹ multiple `outputs` are [not yet supported](https://github.com/moby/buildkit/issues/1555)

### outputs

Following outputs are available

| Name       | Type    | Description           |
|------------|---------|-----------------------|
| `imageid`  | String  | Image ID              |
| `digest`   | String  | Image digest          |
| `metadata` | JSON    | Build result metadata |

## Troubleshooting

See [TROUBLESHOOTING.md](TROUBLESHOOTING.md)

## Contributing

Want to contribute? Awesome! You can find information about contributing to
this project in the [CONTRIBUTING.md](/.github/CONTRIBUTING.md)