What to monitor with Nagios

• Ping
• CPU Usage
• Memory Usage
• Load Average
• Disk Space
• Back-up (see if back-up is done on regular basis, whether it is successful, etc)
• Procs (Programs running on servers)
• DFS
• DHCP
• DNS
• Print spooler
• Uptime
• Incoming Packets
• Outgoing Packets
• UPS Battery Charge
• UPS Battery Runtime Remaining
• UPS Battery Temperature
• UPS Input Voltage
• UPS Input Frequency
• UPS Output Voltage
• UPS Output Frequency
• UPS Output Load
• Active Directory
• Server Chassis Temperature
• Server Ambient Temperature
• Total Running Processes (for *nix servers)
• Reboot Status
• Toner/Cartridge Levels
• Total Processes
• SWAP