https://github.com/jonashackt/docker-hello-world
Example hello world container showing how to use GitHub Container Registry
https://github.com/jonashackt/docker-hello-world
alpine docker github-actions github-container-registry go hello-world
Last synced: 11 months ago
JSON representation
Example hello world container showing how to use GitHub Container Registry
- Host: GitHub
- URL: https://github.com/jonashackt/docker-hello-world
- Owner: jonashackt
- License: mit
- Created: 2021-02-24T08:51:53.000Z (almost 5 years ago)
- Default Branch: main
- Last Pushed: 2024-12-06T03:44:33.000Z (about 1 year ago)
- Last Synced: 2025-02-27T07:42:58.769Z (12 months ago)
- Topics: alpine, docker, github-actions, github-container-registry, go, hello-world
- Language: Go
- Homepage:
- Size: 2.09 MB
- Stars: 14
- Watchers: 3
- Forks: 26
- Open Issues: 7
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# docker-hello-world
[](https://github.com/jonashackt/docker-hello-world/actions)
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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](https://github.com/jonashackt/molecule-ansible-docker-aws/runs/1968417806?check_suite_focus=true) 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](https://medium.com/faun/migrating-my-docker-images-to-the-github-container-registry-9f304ccf0aaa) 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:
```shell
docker run ghcr.io/jonashackt/hello-world
```
### A simple Go executable
The [original hello-world image from Docker](https://github.com/docker-library/hello-world) 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](hello-world.go):
```go
package main
import "fmt"
func main() {
fmt.Println("Hello from Docker on GitHub Container Registry!\nThis message shows that your installation appears to be working correctly.\n\nAs Docker Inc introduced rate-limiting in https://www.docker.com/increase-rate-limits\nwe simply need our own hello-world image on GitHub Container Registry.\n\nTo generate this message, Docker took the following steps:\n 1. The Docker client contacted the Docker daemon.\n 2. The Docker daemon pulled this \"hello-world\" image from the GitHub Container Registry.\n (amd64)\n 3. The Docker daemon created a new container from that image which runs the\n executable that produces the output you are currently reading.\n 4. The Docker daemon streamed that output to the Docker client, which sent it\n to your terminal.\n\n")
}
```
Build it (you need to have go installed with like `brew install go`) with:
```shell
go build hello-world.go
```
This produces a `hello-world` executable you can simply run with `./hello world`.
### A Docker multistage Build for GO
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:
```shell
$ docker images
golang latest 861b1afd1d13 7 days ago 862MB
```
Therefore let's split our [Dockerfile](Dockerfile) a bit:
```dockerfile
# We need a golang build environment first
FROM golang:1.16.0-alpine3.13
WORKDIR /go/src/app
ADD hello-world.go /go/src/app
RUN go build hello-world.go
# We use a Docker multi-stage build here in order that we only take the compiled go executable
FROM alpine:3.13
COPY --from=0 "/go/src/app/hello-world" hello-world
ENTRYPOINT ./hello-world
```
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:
```shell
$ docker build . --tag hello-world
$ docker run hello-world
Hello from Docker on GitHub Container Registry!
This message shows that your installation appears to be working correctly.
As Docker Inc introduced rate-limiting in https://www.docker.com/increase-rate-limits
we simply need our own hello-world image on GitHub Container Registry.
To generate this message, Docker took the following steps:
1. The Docker client contacted the Docker daemon.
2. The Docker daemon pulled this "hello-world" image from the GitHub Container Registry.
(amd64)
3. The Docker daemon created a new container from that image which runs the
executable that produces the output you are currently reading.
4. The Docker daemon streamed that output to the Docker client, which sent it
to your terminal.
```
The resulting image is around `7.55MB` which should be small enough for our use cases.
### Publish the Docker image to GitHub Container Registry
We follow the full guide here: https://docs.github.com/en/packages/guides/pushing-and-pulling-docker-images
#### Activate improved container support
First we need to activate the Container Registry beta feature in our account: https://docs.github.com/en/packages/guides/enabling-improved-container-support
#### Authenticate and login to GitHub Container Registry using GITHUB_TOKEN
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](.github/workflows/publish.yml) should look like this:
```yaml
name: publish
on: [push]
jobs:
publish-hello-world-image:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v2
- name: Build the hello-world Docker image
run: |
echo ${{ secrets.GITHUB_TOKEN }} | docker login ghcr.io -u ${{ github.actor }} --password-stdin
```
or Alternatively we can also use the [docker/login-action](https://github.com/docker/login-action) to to the login:
```yaml
- name: Login to GitHub Container Registry
uses: docker/login-action@v1
with:
registry: ghcr.io
username: ${{ github.actor }}
password: ${{ secrets.GITHUB_TOKEN }}
```
#### Publish (Push) Container image to GHCR
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:
```yaml
docker build . --tag ghcr.io/jonashackt/hello-world:latest
docker run ghcr.io/jonashackt/hello-world:latest
docker push ghcr.io/jonashackt/hello-world:latest
```
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](Dockerfile):
```dockerfile
LABEL org.opencontainers.image.source="https://github.com/jonashackt/docker-hello-world"
```
With this label the image package gets automatically linked to our repository:
And also the image becomes visible on our repositories main page:
#### Make your image publicly accessible
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:
```shell
docker pull ghcr.io/jonashackt/hello-world:latest
docker run ghcr.io/jonashackt/hello-world:latest
```