How do I show the free memory on a Linux system?

You can show free memory on a Linux system with the free command, like this:

free

That command returns results like this:

            total       used       free     shared    buffers     cached
Mem:       8145044    8097552      47492          0      74252    1189464
-/+ buffers/cache:    6833836    1311208
Swap:     12578884    6205424    6373460

If you prefer to see information in MB you can use the -m parameter, like this:

free -m

to get results like this:

            total       used       free     shared    buffers     cached
Mem:          7954       7931         23          0         73       1172
-/+ buffers/cache:       6685       1269
Swap:        12284       6059       6224

Finally, here's the full usage information for the free command:

usage: free [-b|-k|-m|-g] [-l] [-o] [-t] [-s delay] [-c count] [-V]
  -b,-k,-m,-g show output in bytes, KB, MB, or GB
  -l show detailed low and high memory statistics
  -o use old format (no -/+buffers/cache line)
  -t display total for RAM + swap
  -s update every [delay] seconds
  -c update [count] times
  -V display version information and exit

The top utility

If you'd like to see a real-time view of the memory use of applications running on your system you can use the top utility by just typing top at the command line:

top

This starts up an interactive utility you can work with. Keeping with the "memory" theme of this blog post, type a capital letter "M", and top will sort the output by memory used by each running process. After you've seen everything you need, just type "q" to quit the top utility.