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https://github.com/outillage/kaniko-action

Build and push docker images using Kaniko and GitHub actions
https://github.com/outillage/kaniko-action

Last synced: 3 months ago
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Build and push docker images using Kaniko and GitHub actions

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# Kaniko image builder



This Action uses the [kaniko](https://github.com/GoogleContainerTools/kaniko) executor instead of the docker daemon. Kaniko builds the image

by extracting the filesystem of the base image, making the changes in the user space, snapshotting any change and appending it to the base

image filesystem.



This allows for a quite efficient caching, that can be pushed to another docker registry and downloaded on-demand, and a noticeably easier and

more secure secret passing to the build context, as it happens in the user space itself.



## Usage



## Example pipeline

```yaml

name: Docker build

on: push

jobs:

  docker:

    runs-on: ubuntu-latest

    steps:

      - uses: actions/checkout@master

      - name: Kaniko build

        uses: aevea/action-kaniko@master

        with:

          image: aevea/kaniko

          username: ${{ secrets.DOCKERHUB_USERNAME }}

          password: ${{ secrets.DOCKERHUB_PASSWORD }}

          cache: true

          cache_registry: aevea/cache

```



## Required Arguments



This action aims to be as flexible as possible, so it tries to define the defaults as for what I thought of being

the most used values. So, technically there is a single required argument



| variable         | description                                              | required | default                     |

|------------------|----------------------------------------------------------|----------|-----------------------------|

| image            | Name of the image you would like to push                 | true     |                             |



## Optional Arguments



| variable              | description                                                     | required | default         |

|-----------------------|-----------------------------------------------------------------|----------|-----------------|

| registry              | Docker registry where the image will be pushed                  | false    | docker.io       |

| username              | Username used for authentication to the Docker registry         | false    | $GITHUB_ACTOR   |

| password              | Password used for authentication to the Docker registry         | false    |                 |

| tag                   | Image tag                                                       | false    | latest          |

| cache                 | Enables build cache                                             | false    | false           |

| cache_ttl             | How long the cache should be considered valid                   | false    |                 |

| cache_registry        | Docker registry meant to be used as cache                       | false    |                 |

| cache_directory       | Filesystem path meant to be used as cache                       | false    |                 |

| build_file            | Dockerfile filename                                             | false    | Dockerfile      |

| extra_args            | Additional arguments to be passed to the kaniko executor        | false    |                 |

| strip_tag_prefix      | Prefix to be stripped from the tag                              | false    |                 |

| skip_unchanged_digest | Avoids pushing the image if the build generated the same digest | false    |                 |

| path                  | Path to the build context. Defaults to `.`                      | false    | .               |

| tag_with_latest       | Tags the built image with additional latest tag                 | false    |                 |

| target                | Sets the target stage to build                                  | false    |                 |

| debug                 | Enables trace for entrypoint.sh                                 | false    |                 |



**Here is where it gets specific, as the optional arguments become required depending on the registry targeted**



### [docker.io](https://hub.docker.com/)



This is the default, and implicit docker registry, in the same way as with using the docker CLI

In this case, the authentication credentials need to be passed via GitHub Action secrets



```yaml

with:

  image: aevea/kaniko

  username: ${{ secrets.DOCKERHUB_USERNAME }}

  password: ${{ secrets.DOCKERHUB_PASSWORD }}

```



> NOTE: Dockerhub doesn't support more than one level deep of docker images, so Kaniko's default approach of pushing the cache to `$image/cache`

doesn't work. If you want to use caching with Dockerhub, create a `cache` repository, and specify it in the action options.



```yaml

with:

  image: aevea/kaniko

  username: ${{ secrets.DOCKERHUB_USERNAME }}

  password: ${{ secrets.DOCKERHUB_PASSWORD }}

  cache: true

  cache_registry: aevea/cache

```



### [ghcr.io](https://github.com/features/packages)



GitHub's docker registry is a bit special. It doesn't allow top-level images, so this action will prefix any image with the GitHub namespace.

If you want to push your image like `aevea/action-kaniko/kaniko`, you'll only need to pass `kaniko` to this action.



The authentication is automatically done using the `GITHUB_ACTOR` and `GITHUB_TOKEN` provided from GitHub itself. But as `GITHUB_TOKEN` is not

passed by default, it will have to be explicitly set up.



```yaml

with:

  registry: ghcr.io

  password: ${{ secrets.GITHUB_TOKEN }}

  image: kaniko

```



> NOTE: GitHub's docker registry is structured a bit differently, but it has the same drawback as Dockerhub, and that's that it's not possible

to "namespace" images for cache. In order to use registry cache, just specify the image meant to be used as cache, and Kaniko will push the

cache layers to that image instead



```yaml

with:

  registry: ghcr.io

  password: ${{ secrets.GITHUB_TOKEN }}

  image: kaniko

  cache: true

  cache_registry: cache

```



### [registry.gitlab.com](https://docs.gitlab.com/ee/user/packages/container_registry)



GitLab's registry is quite flexible, it allows easy image namespacing, so a project's docker registry can hold up to three levels of image

repository names.



```

registry.gitlab.com/group/project:some-tag

registry.gitlab.com/group/project/image:latest

registry.gitlab.com/group/project/my/image:rc1

```



To authenticate to it, a username and personal access token must be supplied via GitHub Action Secrets.



```yaml

with:

  registry: registry.gitlab.com

  username: ${{ secrets.GL_REGISTRY_USERNAME }}

  password: ${{ secrets.GL_REGISTRY_PASSWORD }}

  image: aevea/kaniko

```



> NOTE: As GitLab's registry does support namespacing, Kaniko can natively push cached layers to it, so only `cache: true` is necessary to be

specified in order to use it.



```yaml

with:

  registry: registry.gitlab.com

  username: ${{ secrets.GL_REGISTRY_USERNAME }}

  password: ${{ secrets.GL_REGISTRY_PASSWORD }}

  image: aevea/kaniko

  cache: true

```



### Other registries



If you would like to publish the image to other registries, these actions might be helpful



| Registry                                             | Action                                        |

|------------------------------------------------------|-----------------------------------------------|

| Amazon Webservices Elastic Container Registry (ECR)  | https://github.com/elgohr/ecr-login-action    |

| Google Cloud Container Registry                      | https://github.com/elgohr/gcloud-login-action |



### Other arguments details



#### tag



The `tag` argument, **unless overridden**, is automatically guessed based on the branch name. If the branch is `master` then the tag will

be `latest`, otherwise it will keep the branch name, but replacing any forward slash (/) with a hyphen (-).



If the `v` prefix that it's usually added to the GitHub releases is not desired when pushed to dockerhub, the `strip_tag_prefix` allows to

specify which part of the tag should be removed.



Example:



```yaml

with:

  registry: ghcr.io

  password: ${{ secrets.GITHUB_TOKEN }}

  image: kaniko

  strip_tag_prefix: pre-

```



for the tag `pre-0.1` will push `kaniko:0.1`, as the `pre-` part will be stripped from the tag name.



## Outputs



### `image`



Full reference to the built image with registry and tag.