Keep track of vital system statistics and troubleshoot performance problems with Munin on Ubuntu 12.04 (Precise Pangolin).
How to use top to monitor a server's performance.
Cacti is a powerful server monitoring solution that uses SNMP to track resource usage on Ubuntu 12.04 (Precise).
Improve uptime with Monit Server Monitoring. Monit will watch you system around the clock, and respond to out-of-the-norm events by following your instructions.
Use the vmstat tool to monitor your system's virtual memory usage.
Use Nagios to monitor services and send status updates on your Ubuntu 12.04 (Precise Pangolin) VPS.
Use Logwatch to generate digests and analyze your server logs