How to cite a website/manual where the authors are (mostly) unknown?
You can cite using @misc without Author field. To to that, you need to include a key field. Here is an example:

@misc{KubernetesManual2017,
    title = {{Kubernetes Manual}},
    howpublished = "\url{please put the url}",
    year = {2017}, 
    note = "[Online; accessed 04-Dec-2017]",
    key = "KubernetesManual2017",
}