# nagios > Legacy host/service/networking monitoring program. > Largely deprecated by `nagios4`. > See also: `nagios2`, `nagios3`, `nagios4`. > More information: . - Start `nagios`: `nagios /etc/nagios/nagios.cfg` - Start `nagios` in daemon mode: `nagios -d` - Start `nagios`, print service check scheduling information to `stdout`, then shutdown: `nagios -s` - Verify configuration file: `nagios -v`