For example, I have an internal docker registry for my kube cluster, hosted on internal-docker-registry.io:5000.
When the pod from the kube cluster pulling image busybox, I don't want to pull from docker hub docker.io. But instead I want it to pull from internal-docker-registry.io:5000.
Note that I cannot change the image name to internal-docker-registry.io:5000/busybox since I don't own the spec and there are too man these kind of third party image in my cluster.
Here you can find a complete guide on how to accomplish this in the official kubernetes documentation 1
1 https://kubernetes.io/docs/tasks/configure-pod-container/pull-image-private-registry/
I have posted community wiki answer to summarize the topic:
As David Maze well mentioned in the comment:
there is no "image registry search list"; an image name without a registry always uses
docker.io, to avoid surprises where e.g.FROM ubuntumeans something different depending on local configuration.
So if you can't change the image name to internal-docker-registry.io:5000/busybox then unfortunately you don't have the option to get the image from your private registry (according to David's comment).
See also similar questions:
How to change the default docker registry from docker.io to my private registry?