HTTPS is a protocol for secure communication over a computer network which is widely used on the Internet. HTTPS consists of communication over Hypertext Transfer Protocol (HTTP) within a connection encrypted by Transport Layer Security or its predecessor, Secure Sockets Layer. The main motivation for HTTPS is authentication of the visited website and protection of the privacy and integrity of the exchanged data. Intro Courtesy Wikipedia Full SSL support requires Nagios XI version 2011R1.6 or later. Before we start. Check if the below packages are install, they should be if you are using latest Nagios XI, but check them anyways. yum install mod_ssl openssl Creating Key and Certificate Lets generate the key for the server. openssl genrsa -out ca.key 2048 Output for the command. [ahmed@nagiosserver ~]$ openssl genrsa -out ca.key 2048 Generating RSA private key, 2048 bit long modulus ...........................................................................................