**Linux** is one of the most popular open source operating system and comes with huge set of commands. The most important and single way of determining the total available space of the **physical memory** and **swap memory** is by using “**free**” command.
The Linux “**free**” command gives information about total used and available space of **physical memory** and **swap memory** with **buffers** used by kernel in **Linux/Unix** like operating systems.
This article provides some useful examples of “**free**” commands with options, that might be useful for you to better utilize memory that you have.
### 1. Display System Memory ###
Free command used to check the used and available space of **physical memory** and **swap memory** in **KB**. See the command in action below.
# free
total used free shared buffers cached
Mem: 1021628 912548 109080 0 120368 655548
-/+ buffers/cache: 136632 884996
Swap: 4194296 0 4194296
### 2. Display Memory in Bytes ###
Free command with option **-b**, display the size of memory in **Bytes**.
