The free command is used to view how much memory (RAM) is available. The free command without any options will display the available memory in bytes.

~]# free
              total        used        free      shared  buff/cache   available
Mem:       10054428     5930312      297116      217544     3827000     3592572
Swap:       8388604       45056     8343548

Typically, the -h or --human option is used to view the available memory rounded:

• B = bytes
• K = kilobytes
• M = megabytes
• G = gigabytes
• T = terabytes
• P = petabytes

~]# free --human
              total        used        free      shared  buff/cache   available
Mem:           9.6G        5.7G        289M        212M        3.7G        3.4G
Swap:          8.0G         44M        8.0G

The --total flag can be used to print the total memory (mem + swap).

~]$ free --human --total
              total        used        free      shared  buff/cache   available
Mem:            15G        5.7G        3.3G        107M        6.5G        9.4G
Swap:          8.0G          0B        8.0G
Total:          23G        5.7G         11G

The following options can be used to round the values.

• -b or --bytes
• -k or --kilo
• -m or --mega
• -g or --giga
• --tera
• --peta

~]$ free --giga
              total        used        free      shared  buff/cache   available
Mem:              9           5           0           0           3           3
Swap:             7           0           7

The -s or --seconds option can be used to rediplay the output every x seconds. Optionally, the --count option can be used to limit the number of times the output will be redisplayed, such as 10 times in this example.

free --seconds 1 --count 10

If swap memory free is low, refer to Linux Fundamentals - Analyzing swap memory.