Originally posted by @brandond in #12439 (reply in thread)

do you have a working registries.yaml that allows k3s' containerd to access a private registry?

It looks like this works for me:

 configs:
   registry-1.docker.io:
     auth:
       username: brandond
       password: dckr_pat_xxx

I'm not sure why using the docker.io alias does not work, if this is a bug or intentional BUT I will note that the containerd docs linked above also refer to docker.io as registry-1.docker.io in some places, and registry-1.docker.io IS the actual registry endpoint for docker hub's registry service.

docker.io and registry-1.docker.io should be handled interchangeably. Need to investigate if this is a bug in upstream containerd, or if it was regressed in our mirror support patch.