Hi @Sami Ahmad Try postgresql-server https://www.digitalocean.com/community/tutorials/how-to-install-and-use-postgresql-on-centos-7 As always, if you find this post useful please "accept" the answer. ... View more

@Robin Dong In Linux only iptables controls the Kernel based firewall. You might have firewalld in CentOS7 or ufw in Ubuntu but they're just an abstraction layer on top of iptables. So if 'iptables -L' doesn't show anything then it's all good. The Ambari iptables check is rudimentary and it doesn't know if the rules that exist still allow all the traffic. It only checks for 'service iptables status' or 'systemctl status firewalld', which means there are no filter tables. But please be aware of the cloud firewall as well. For example in AWS even instances in the same Security Group are not allowed by default to communicate with each another and this must be enabled explicitly: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/security-group-rules-reference.html#sg-rules-other-instances ... View more