x509: certificate signed by unknown authority error reported during docker pull from Red Hat registry

Issue

• We noticed that we can no longer pull images from the Red Hat registry. Error message from docker is as following.

[root@foobar ]# docker pull registry.access.redhat.com/rhel7.1
Using default tag: latest
Trying to pull repository registry.access.redhat.com/rhel7.1 ... 
Pulling repository registry.access.redhat.com/rhel7.1
Error while pulling image: Get https://registry.access.redhat.com/v1/repositories/rhel7.1/images: x509: certificate signed by unknown authority