Installing and configuring Nagios

Nagios is a well-known monitoring tool. We won't make any claims that it is the best or most suited tool for watching a highly available PostgreSQL installation. However, the community is large, the functionality is extensive and established, and interoperability with other tools and libraries is high.

As an unfortunate consequence, the amount of installation prerequisites is rather lengthy. To get Nagios working properly, we need an HTTP server, Perl, and a mail daemon. Some plugins require PHP, while others need MySQL, SNMP, or any number of esoteric utilities and acronyms. There might be DBAs who also have strong skills as webmasters, but we can't depend on that. Getting Nagios installed with all of its foundation services is very complex, so we don't recommend that you do so.

Due to its history, the likelihood that Nagios is available on major Linux distributions is very high. Installing Nagios through the distribution will handle most, if not all, configuration...