When you specify a HEAD request to /v2/<name>/manifests/<reference> for an existing docker image in a Nexus docker repository, a 404 error will occur.
For example, I have tried to send a HEAD request to something like http://host:8081/respository/dockerRepo/v2/test/alpine/manifests/latest and I get back a 404.
However, if I try a GET request to http://host:8081/respository/dockerRepo/v2/test/alpine/manifests/latest, I get back a response with the details that I am looking for.
In contrast, in a Docker registry, a HEAD request to http://host:8081/v2/test/alpine/manifests/latest works properly.
For more details about the API call, you can go to "https://docs.docker.com/registry/spec/api/#pulling-an-image" and look for "Existing Manifests"
The HEAD request should be supported in Nexus docker repositories and not be a 404 error.