Why does my Gitea action push a Docker image with a 404 error?

The short answer is: No—you’re not using the wrong build action. The "v2" in the URL is standard; it represents the Docker Registry HTTP API v2 that most registries implement.

When you see a 404 on the endpoint (for example, /v2/ebooks/blobs/uploads/), it indicates that the registry endpoint isn’t found. This is most often due to one of these factors:

• Repository auto-creation: Some registries (like Docker Hub) will automatically create a new repository when you push an image, but the Gitea Docker registry might require you to create the repository (“ebooks” in your case) ahead of time.
• Registry configuration: The Gitea Docker registry could be misconfigured or missing support for the complete Docker Registry API v2 (especially for upload endpoints). Verify that your Gitea instance is correctly set up to support pushing images.
• Certificate or URL issues: If your registry uses self-signed certificates or an unexpected URL format, that might cause issues too (although your docker login step works, it’s something to rule out).

The docker/build-push-action@v5 is a fully supported action for building and pushing images. Downgrading to a previous version (such as v4) wouldn’t change the fact that Buildx and the Docker client use the registry API v2. Instead, the 404 suggests that the Gitea registry isn’t exposing the expected endpoint.

What to Do Next

1. Manually Create the Repository:
   Check if you need to create the "ebooks" repository in Gitea manually so that the push has a valid target.

2. Review Gitea Registry Settings:
   Cross-check your Gitea configuration and documentation to ensure that the Docker registry support is enabled and correctly configured. Some settings might affect how endpoints are exposed.

3. Check for Known Issues:
   Look for any known issues or discussions regarding the Gitea provided registry. There might be additional configuration needed (such as enabling automatic repository creation) or version-specific quirks.

4. If Needed, Consider Alternatives:
   Although switching to docker/build-push-action@v4 might feel like a workaround, it may not resolve the issue because the underlying push call will still use the Docker Registry API v2 endpoints. It’s best to resolve the configuration problem with the registry.

In summary, you’re using the correct build-push action version. The 404 error is coming from the Gitea registry not recognizing the expected API endpoint. Addressing the registry’s configuration or ensuring that the target repository exists should resolve your issue.