The convenience and reliability that monitoring programs offer system administrators is astounding. Whether at home, commuting, or on vacation, admins can continuously monitor their networks, learning of issues long before they become catastrophes.
Nagios, the most popular open source solution for system and network monitoring, is extremely robust, but it’s also intensely complex.
Nagios is free, open source host, service and network monitoring services. Nagios provides an extensible framework, that can monitor pretty much anything using plugins.
You can find the memory used by a program (process) by looking into /proc directory or using standard command such as ps or top. However, you must calculate all memory usage by hand i.e. add Shared Memory + mapped file + total virtual memory size of the process + Resident Set Size + non-swapped physical [...]
Q. How can I find out Linux Resource utilization using vmstat command? How do I get information about high disk I/O and memory usage? A. vmstat command reports information about processes, memory, paging, block IO, traps, and cpu activity. However, a real advantage of vmstat command output – is to the point and (concise) easy [...]
You can use the watch command to execute a program or shell script periodically, display its output on screen repeatedly. This allows you to watch the program output change over time. By default, the program is run every 2 seconds. This is useful to monitor memory utilization or disk space usage over time without having to look at scrolling output.