Sometimes, executing the below commands in Ubuntu server also returns an unrecognized service message, service iptables save. This command works based on the startup script of iptables in the folder /etc/init.d. Usually, this command will work for RHEL/ Red Hat / CentOS. In Ubuntu, to save the changes in firewall rules, we use the following. Redis is a fast, versatile in-memory key-value store. With its rapid response, it is mainly used in the caching layer. What is Redis Server? Redis stands for Remote Dictionary, and was founded when its founder Salvatore Sanfilippo wanting to improve his startup's scalability.