Linux and Unix systems as a rule log system-relevant events through syslog. Sooner or later you will probably want Nagios to also inform the administrator of important syslog events. To do this, you require passive service checks, NSCA for transmitting the results to the Nagios server, and a method of filtering individual block entries.
If you are using
syslog-ng instead of the standard BSD syslog, you can make use of its ability to set filters and to format the output using templates. The use of NSCA compensates for the fact that the program cannot itself transmit data in encrypted form.
This connection to Nagios is supplemented by programs to evaluate log files, such as