Since everything in Linux/Unix is a file, Linux has some interesting ways to monitor for problems. Often systems administrators monitor CPU, Ram, Disk Space, and Network Usage. These are all valid data points and are especially useful for capacity planning. For real time detection of problems, especially with web/application/databases, these are not always the best indicators. In my experience, checking and trending the number of open sockets, pipes, files, tcp/udp sockets, and unix sockets has been the single best indicator of a problem. These have been much better than CPU, Load, or I/O Wait. In fact, under optimal usage of server hardware, one would expect spikes in CPU, RAM, and I/O.
Instructions: http://crunchtools.com/software/cruncht ... pes-files/
Versioned Code: http://code.google.com/p/crunchtools/so ... ipes_files