“docker pull” certificate signed by unknown authority

Question

I was trying to pull a docker image from a docker registry but hit the following issue:

$ docker pull //          


        

Answer 1

By default docker keeps a local Certificate store, in Centos:/etc/sysconfig/docker. In Organizations, the servers usually comes preinstalled with it's own Root Cert. So if you use cert issued by the organization, docker will not be able to find the organization's Root Cert. when it refers to its local store. So either you can remove the reference to its local store in /etc/sysconfig/docker or you can delete it's local Certificate store (Centos:/etc/docker/certs.d). Restarting docker service after you make the change will resolve this issue.