Thefree command displays the total amount of free and used physical and swap memory in the system, as well as the buffers used by the kernel.<br /> Display free memory size in MB:
free -m
Displays a line containing the totals memory in MB:
free -t -m
Thevmstat command reports information about processes, memory, paging, block IO, traps, and CPU activity.
vmstat
Thetop command which provides a dynamic real-time view of a running system.
top
PressSHIFT+M to sort on memory utilization.<br /> Pressz to colorize.<br /> Press1 to see multiple CPU's.<br /> Pressq to quit.
For more help type ' _command–help' or 'man _command'
– FredPettis - 02 Jun 2009