free

The free command outputs memory and swap information, much as the top command does. With no options, free shows the information in kilobytes:

# free              total       used       free     shared    buffers      cached Mem:        511996     501616      10380          0      60224      359336 -/+ buffers/cache:      82056     429940 Swap:       105832        884     104948

The free command has a handful of options. We recommend -mt. The -m switch causes the output to be in megabytes, and the -t switch provides a total line:

# free -mt              total       used       free     shared    buffers      cached Mem:           499        489         10          0         58         350 -/+ buffers/cache:         80        419 Swap:          103          0        102 Total:         603        490        112