The free command is a powerful utility for monitoring memory usage on Linux systems. It provides detailed information about the total amount of memory available, used, and free on the system, as well as swap usage. In this article, we will explore how to use the free command to display memory statistics on a Linux system.

When you run the free command without any arguments, it will display memory statistics in kilobytes. The output will look something like this:

total        used        free      shared  buff/cache   available
Mem:       16385692     4426388     7912212      282888     4045092    10988616
Swap:       4194300           0     4194300

Here’s a breakdown of what each column represents:

• total: the total amount of physical memory available on the system
• used: the amount of memory currently in use
• free: the amount of memory that is not being used by any process
• shared: the amount of memory shared between processes
• buff/cache: the amount of memory used for buffers and cache
• available: an estimate of how much memory is available for starting new applications

If you want to display the memory statistics in a more human-readable format, you can use the -h option with the free command. This will output the memory usage in gigabytes, megabytes, or kilobytes depending on the size of the memory:

total        used        free      shared  buff/cache   available
Mem:           15G         4G         7G       276M         3G         10G
Swap:           4G           0         4G

You can also use the -b, -k, -m, or -g options to display memory statistics in bytes, kilobytes, megabytes, or gigabytes respectively. For example, to display memory statistics in megabytes, you can use the following command:

free -m

In addition to displaying memory statistics, the free command also provides information on swap usage. Swap is a space on the hard drive that is used by the operating system as virtual memory when the physical memory (RAM) is full. The free command displays the total amount of swap space, used swap space, and free swap space on the system. If the used swap space is constantly high, it may indicate that the system is running out of physical memory and is relying heavily on swap space.

In conclusion, the free command is a valuable tool for monitoring memory usage on Linux systems. By using this command, administrators can quickly check memory statistics and identify any issues related to memory usage on the system. Whether you need to check the total amount of memory available, monitor swap usage, or analyze memory trends over time, the free command has got you covered.