add workflow for multiarch & ghcr support

[azrikahar]

Overview

Preface: To correlate the descriptions/instructions, I will sometimes mention to look at line X of the workflow, which is .github/workflow/publish-image.yml.

Multi Architecture support

Resolves #34

This PR introduces a github action workflow to automate building volume-backup into 3 architectures (refer line 36 of workflow), namely:

• linux/amd64
• linux/arm64
• linux/arm/v7

Setup referenced from https://github.com/docker/build-push-action/blob/master/docs/advanced/multi-platform.md

Pushes to DockerHub and GHCR at the same time

Resolves #35

Refer line 20-31 of workflow. The tags in the end (line 39-40), particular ghcr.io prefix, indicates to the docker/build-push-action@v2 step to push to each of the registry.

Setup referenced from https://github.com/docker/build-push-action/blob/master/docs/advanced/push-multi-registries.md

How does the workflow triggers

The trigger for the github action is manual (on workflow_dispatch, line 3-4 of workflow).

The maintainers can go to Actions tab, click on publish-image workflow on the left, click on Run workflow on the bottom right there, then click on the green Run workflow button to trigger it. A sample screenshot depicting the steps is shown below:

Proof of workflow working in my forked repo

Terminal screenshot on a Raspberry Pi on arm64 architecture

• Pulling the image from both DockerHub and ghcr:
  
• Backing up an existing out-of-the-box nginx data volume and showing the content:
  

Published images

• Link to Github Container Registry: https://github.com/azrikahar/volume-backup/pkgs/container/volume-backup
• Link to DockerHub: https://hub.docker.com/r/azrikahar/volume-backup

Action items needed for maintainers before merging this PR

2 new repository secrets are needed to be created in order for the github action step Login to Dockerhub to use secrets.DOCKERHUB_USERNAME & secrets.DOCKERHUB_TOKEN (line 23-24) to login to loomchild dockerhub account successfully to push the resulting image.

Sample screenshot:

Reference from github docs: https://docs.github.com/en/actions/reference/encrypted-secrets

As for the secrets.GITHUB_TOKEN on line 31, it is generated automatically for us so we don't have to do anything here. Refer official docs here

Once the 2 dockerhub secrets are added and the PR is merged, the maintainers will just need to trigger the workflow once to resolve the 2 issues referenced in the beginning.

[loomchild]

Hi and thanks for submitting this! I will review and test it as soon as I can (probably in a few weeks).

[ksurl]

looks good to me

[loomchild]

Sorry for delay. This looks perfect, thank you very much. I will merge it and run some tests. I didn't realize there are docker actions for Buildx and QEMU already.

After the merge I will configure it to trigger on every push.

[azrikahar]

Sorry for delay. This looks perfect, thank you very much. I will merge it and run some tests. I didn't realize there are docker actions for Buildx and QEMU already.

After the merge I will configure it to trigger on every push.

No worries, glad it works!

In hindsight, just noticed I should've mentioned the manual workflow trigger was just a temp solution since my intention was to let you decide what trigger(s) suit your need haha. Cheers