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Example hello world container showing how to use GitHub Container Registry
As Docker Inc introduced a rate-limiting https://www.docker.com/increase-rate-limits I began to bump into problems like this while running a simple docker run hello-world on GitHub Actions:
Unable to find image 'hello...se the limit by authenticating and upgrading: https://www.docker.com/increase-rate-limit.\nSee 'docker run --help'.\n"
Many people started to migrate their Docker images to the new GitHub Container Registry, which is currently in public beta: https://docs.github.com/en/packages/guides/pushing-and-pulling-docker-images
And there are already many projects that are simply not available anymore on DockerHub - but on GitHub Container Registry (like https://hub.docker.com/r/oracle/graalvm-ce to https://github.com/orgs/graalvm/packages/container/package/graalvm-ce)
Well I thought why not crafting a simple and small hello-world image and publish it to GitHub Container Registry?!
TLDR; Simply run it with:
The original hello-world image from Docker also uses a small executable to print a text. I decided to go with golang to create a ultra-small executable myself.
So there's hello-world.go:
Build it (you need to have go installed with like brew install go) with:
This produces a hello-world executable you can simply run with ./hello world.
As we only need to have Go runtime stuff present to build the binary, we should implement a Docker multi-stage build. Since the GO Docker image https://hub.docker.com/_/golang is quite huge:
Therefore let's split our Dockerfile a bit:
The second "run" image is based on the same https://hub.docker.com/_/alpine image as the builder image containing the GO runtimes.
Now let's build and run our image:
The resulting image is around 7.55MB which should be small enough for our use cases.
We follow the full guide here: https://docs.github.com/en/packages/guides/pushing-and-pulling-docker-images
First we need to activate the Container Registry beta feature in our account: https://docs.github.com/en/packages/guides/enabling-improved-container-support
From March 2021 on we should be able to use our GITHUB_TOKEN to authenticate against the GitHub Container Registry instead of using a separate PAT (see https://github.blog/changelog/2021-03-24-packages-container-registry-now-supports-github_token/)!
So our GHA workflow file publish.yml should look like this:
or Alternatively we can also use the docker/login-action to to the login:
The final step now is to push our container image to the GitHub Container Registry. Therefore we need to tag our image correctly while building it using ghcr.io/OWNER/IMAGE_NAME:latest. After that we can push it:
To link our image to our GitHub repository (this isn't done automatically since images are treated as GH account global packages), we add a LABEL into our Dockerfile:
With this label the image package gets automatically linked to our repository:
And also the image becomes visible on our repositories main page:
Per default our container image is private on GitHub Container Registry: https://docs.github.com/en/packages/guides/configuring-access-control-and-visibility-for-container-images
To make it publicly accessible we need to move to our user account or orga page. For my account this is https://github.com/jonashackt?tab=packages
Now click on the image published (which looks the same as a normal GH package) and then go to Package Settings. Now in the Danger Zone click on change visibility and choose public:
We should finally be able to pull and run our image! Just run:
Example hello world container showing how to use GitHub Container Registry
