List Information About RAM And Swap Memory In Your Linux Machine

Syntax And Eg: Total RAM on this system is 4GB. The values displayed below are in KB.
 root@ubuntu:~#  free
             total       used       free     shared    buffers     cached
Mem:       3786324     685240    3101084          0      35256     449424
-/+ buffers/cache:     200560    3585764
Swap:      4186108          0    4186108
The values displayed below are in MB.
root@ubuntu:~# free -mto
             total       used       free     shared    buffers     cached
Mem:          3697        669       3028          0         34        438
Swap:         4087          0       4087
Total:        7785        669       7116
In the following command:
    option m displays the values in MB
    option t displays the “Total” line, which is sum of physical and swap memory values
    option o is to hide the buffers/cache line from the above example.