ERROR: x509: certificate signed by unknown authority, when you docker login on OCP4.

Issue

• Even though you has deployed CA certificate of OCP4 to "/etc/docker/certs.d/image-registry-openshift-image-registry.apps.ocp4.example.com/ca.crt", the following error message is shown.

# docker login -u $USERNAME -p $TOKEN image-registry-openshift-image-registry.apps.ocp4.example.com
WARNING! Using --password via the CLI is insecure. Use --password-stdin.
Error response from daemon: Get https://image-registry-openshift-image-registry.apps.ocp4.example.com/v2/: x509: certificate signed by unknown authority