How to specify all images in diun using docker mirrors

[solitudechn]

I don't have direct access to docker.io where I am, so I need to connect to docker mirrors to pull my docker images.
I tried to link my /etc/docker/daemon.json:/root/.docker/config.json:ro file, but it didn't work. I also tried to modify the DIUN_REGOPTS_0_NAM variable, but it didn't work. Is there a better way for me to specify docker mirrors?