buildah-build/README.md

# buildah-build
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Buildah Build is a GitHub Action for building Docker and Kubernetes-compatible images quickly and easily.

[Buildah](https://github.com/containers/buildah/tree/master/docs) only works on Linux. GitHub's [Ubuntu Environments](https://github.com/actions/virtual-environments#available-environments) (`ubuntu-18.04` and newer) come with buildah installed. If you are not using these environments, or if you want to use a different version, you must first [install buildah](https://github.com/containers/buildah/blob/master/install.md).

After building your image, use [push-to-registry](https://github.com/redhat-actions/push-to-registry) to push the image and make it pullable.

<a id="action-inputs"></a>

## Action Inputs

<a id="dockerfile-build-inputs"></a>

### [Inputs for build from containerfile](https://github.com/containers/buildah/blob/main/docs/buildah-build.md)

| Input Name | Description | Default |
| ---------- | ----------- | ------- |
| arch | Label the image with this architecture, instead of defaulting to the host architecture. Refer to [Multi arch builds](#multi-arch-builds) for more information. | None (host architecture)
| build-args | Build arguments to pass to the Docker build using `--build-arg`, if using a Containerfile that requires ARGs. Use the form `arg_name=arg_value`, and separate arguments with newlines. | None
| context | Path to directory to use as the build context. | `.`
| containerfiles* | The list of Containerfile paths to perform a build using docker instructions. This is a multiline input to allow multiple Containerfiles. | **Must be provided**
| extra-args | Extra args to be passed to buildah bud. Separate arguments by newline. Do not use quotes. | None
| image | Name to give to the output image. | **Must be provided**
| layers | Set to true to cache intermediate layers during the build process. | None
| oci | Build the image using the OCI format, instead of the Docker format. By default, this is `false`, because images built using the OCI format have issues when published to Dockerhub. | `false`
| tags | The tags of the image to build. For multiple tags, separate by a space. For example, `latest ${{ github.sha }}` | `latest`
> *The `containerfiles` input was previously `dockerfiles`. Now `dockerfiles` is an alias for `containerfiles`. For details see [the issue](https://github.com/redhat-actions/buildah-build/issues/57).

<a id="scratch-build-inputs"></a>

### [Inputs for build without containerfile](https://github.com/containers/buildah/blob/master/docs/buildah-config.md)

| Input Name | Description | Default |
| ---------- | ----------- | ------- |
| arch | Label the image with this architecture, instead of defaulting to the host architecture. Refer to [Multi arch builds](#multi-arch-builds) for more information. | None (host architecture)
| base-image | The base image to use for the container. | **Must be provided**
| content | Paths to files or directories to copy inside the container to create the file image. This is a multiline input to allow you to copy multiple files/directories.| None
| entrypoint | The entry point to set for the container. This is a multiline input; split arguments across lines. | None
| envs | The environment variables to be set when running the container. This is a multiline input to add multiple environment variables. | None
| image | Name to give to the output image. | **Must be provided**
| oci | Build the image using the OCI format, instead of the Docker format. By default, this is `false`, because images built using the OCI format have issues when published to Dockerhub. | `false`
| port | The port to expose when running the container. | None
| tags | The tags of the image to build. For multiple tags, separate by a space. For example, `latest ${{ github.sha }}` | `latest`
| workdir | The working directory to use within the container. | None

<a id="outputs"></a>

## Action Outputs

`image`: The name of the built image.<br>
For example, `spring-image`.

`tags`: A list of the tags that were created, separated by spaces.<br>
For example, `latest ${{ github.sha }}`.

`image-with-tag`: The name of the image tagged with the first tag present.<br>
For example, `spring-image:latest`

<a id="build-types"></a>

## Build Types

You can configure the `buildah` action to build your image using one or more Containerfiles, or none at all.

<a id="build-using-dockerfile"></a>

### Building using Containerfiles

If you have been building your images with an existing Containerfile, `buildah` can reuse your Containerfile.

In this case the inputs needed are `image` and `containerfiles`. `tag` is also recommended. If your Containerfile requires ARGs, these can be passed using `build-arg`.

```yaml
name: Build Image using Containerfile
on: [push]

jobs:
  build:
    name: Build image
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2

    - name: Buildah Action
      uses: redhat-actions/buildah-build@v2
      with:
        image: my-new-image
        tags: v1 ${{ github.sha }}
        containerfiles: |
          ./Containerfile
        build-args: |
          some_arg=some_value
```
<a id="scratch-build"></a>

### Building without a Containerfile

Building without a Containerfile requires additional inputs, that would normally be specified in the Containerfile.

Do not set `containerfiles` if you are doing a build from scratch. Otherwise those Containerfiles will be used, and the inputs below will be ignored.

- An output `image` name and usually a `tag`.
- `base-image`
  - In a Containerfile, this would be the `FROM` directive.
- `content` to copy into the new image
  - In a Containerfile, this would be `COPY` directives.
- `entrypoint` so the container knows what command to run.
  - In a Containerfile, this would be the `ENTRYPOINT`.
- All other optional configuration inputs, such as `port`, `envs`, and `workdir`.

Example of building a Spring Boot Java app image:
```yaml
name: Build Image
on: [push]

jobs:
  build-image:
    name: Build image without Containerfile
    runs-on: ubuntu-latest

    steps:
    - uses: actions/checkout@v2

    - run: mvn package

    - name: Build Image
      uses: redhat-actions/buildah-build@v2
      with:
        base-image: docker.io/fabric8/java-alpine-openjdk11-jre
        image: my-new-image
        tags: v1
        content: |
          target/spring-petclinic-2.3.0.BUILD-SNAPSHOT.jar
        entrypoint: java -jar spring-petclinic-2.3.0.BUILD-SNAPSHOT.jar
        port: 8080
```

<a id="multi-arch-builds"></a>

## Multi arch builds

Refer to the [multi-arch example](./.github/workflows/multiarch.yml).

### Emulating RUN instructions

Cross-architecture builds from containerfiles containing `RUN` instructions require `qemu-user-static` emulation registered in the Linux kernel.

For example, run `sudo apt install qemu-user-static` on Debian hosts, or `sudo dnf install qemu-user-static` on Fedora.

You can run a [containerized version of the registration](https://hub.docker.com/r/tonistiigi/binfmt) if the package does not exist for your distribution:
```sh
sudo podman run --rm --privileged docker.io/tonistiigi/binfmt --install all
```
This registration remains active until the host reboots.

### The `arch` input
The `arch` argument overrides the Architecture label in the output image. It does not actually affect the architectures the output image will run on. The image must still be built for the required architecture.

There is a simple example [in this issue](https://github.com/redhat-actions/buildah-build/issues/60#issuecomment-876552452).

### Creating a Multi-Arch Image List
Use the [buildah manifest](https://github.com/containers/buildah/blob/main/docs/buildah-manifest.md) command to bundle images into an image list, so multiple image can be referenced by the same repository tag.

There are examples and explanations of the `manifest` command [in this issue](https://github.com/containers/buildah/issues/1590).

This action does not support the `manifest` command at this time, but there is [an issue open](https://github.com/redhat-actions/buildah-build/issues/61).

## Using private images

If your build references a private image, run [**podman-login**](https://github.com/redhat-actions/podman-login) in a step before this action so you can pull the image.
For example:

```yaml
- name: Log in to Red Hat Registry
  uses: redhat-actions/podman-login@v1
  with:
    registry: registry.redhat.io
    username: ${{ secrets.REGISTRY_REDHAT_IO_USER }}
    password: ${{ secrets.REGISTRY_REDHAT_IO_PASSWORD }}
```