There's no shortage of open source server monitoring products out there, but we like Nagios for getting the job done. Nagios can easily be set to monitor server system logs, state of the processor, disk usage, and the like. Nagios monitors protocols such as SMTP, POP3, HTTP, ICMP, SNMP, and FTP, and can handle remote monitoring via SSH or SSL. It even supports external environmental probes. Something you want to monitor that isn't supported? A plug-in can be easily written using common scripting or programming languages. FULL REPORT ...