(Nagios is a monitoring system that monitors system operation status and network information. Nagios can monitor the specified local or remote hosts and services, and provide exception notification function. Nagios can run on the linux/unix platform. At the same time, it provides an optional browser based web interface to facilitate system managers to view network status, various system problems, logs, etc. Main features of Nagios: - monitor network services (SMTP, POP3, HTTP, NNTP, Ping, etc.) - monitor host resources (processes, disks, etc.) - simple plug-in design can easily extend Nagios' monitoring function - concurrent processing of services and other monitoring - error notification function (through email, pager, or other user-defined methods) -You can specify a custom event handling controller - an optional browser based web interface to facilitate system managers to view network status, various system problems, logs, etc. - you can view system monitoring information through your mobile phone)