For Redhat Servers use the following

### Download and save ssl cert to a file dockerhub.crt ###

# echo | openssl s_client -showcerts -servername registry-1.docker.io -connect registry-1.docker.io:443 2>/dev/null | \awk '/-----BEGIN CERTIFICATE-----/,/-----END CERTIFICATE-----/' > dockerhub.crt

the local TLS files should be kept in /etc/pki/ca-trust/source/anchors so copy the dockerhub.crt file to anchors

# cp dockerhub.crt /etc/pki/ca-trust/source/anchors

then use update command to update the same

# update-ca-trust extract

update-ca-trust extract tool merges all of this into the extracted output files under:

/etc/pki/ca-trust/extracted

restart your docker service .

Done