Ways to Check Available Swap Space on Linux Server or Desktop

Knowing how to check available swap space is crucial for managing memory on Linux systems. Whether you're troubleshooting performance issues or planning to optimize resource usage, Linux provides several simple commands to monitor swap space.

In this guide, we’ll explore easy ways to check your system's swap usage on both servers and desktops, to check the available swap space on your Linux server, you can use a few different commands. Here are the most common ones:

1. Using the free Command

The free command provides a summary of the system's memory usage, including swap space.

Run the following command:

free -h

• The -h flag makes the output human-readable (shows the values in GB, MB, etc.).
• In the output, look for the Swap row, which will show the total, used, and free swap space.

Example output:

              total        used        free      shared  buff/cache   available
Mem:           7.7G        2.1G        1.2G        0B        4.4G        5.0G
Swap:          4.0G        0.0G        4.0G

In this example, the system has 4.0 GB of swap space, and none of it is being used (used 0.0G).

2. Using the swapon Command

The swapon command can be used to display detailed information about swap devices and files that are currently in use.

Run this command:

swapon --show

Example output:

NAME      TYPE      SIZE  USED  PRIO
/swapfile file      4.G  B    -2

This shows the swap device or file (e.g., /swapfile), its size, the used space, and its priority.

3. Using the vmstat Command

The vmstat command gives a snapshot of memory and swap usage. You can check swap space using:

vmstat

In the output, look at the si (swap in) and so (swap out) columns to see swap usage:

procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
 r  b   swpd   free   buff  cache   si  so   bi   bo   in   cs us sy id wa st
 1  0      0 4182644 167016 339928    0   0    0    3  999  153  5  1  94  0  0

In this example, there is no swap usage, as swpd (swap used) is 0.

4. Checking Swap Space Using /proc/meminfo

You can also check the swap space by looking at the contents of /proc/meminfo:

cat /proc/meminfo | grep Swap

This will output information about the swap space, such as:

SwapTotal:        4194300 kB
SwapFree:         4194300 kB

• SwapTotal is the total amount of swap space available.
• SwapFree is the amount of swap space that is currently unused.

Summary of Commands:

• free -h: Provides a quick overview of memory and swap usage.
• swapon --show: Displays detailed information about swap devices and files.
• vmstat: Displays memory and swap usage, along with other system stats.
• cat /proc/meminfo | grep Swap: Gives detailed swap statistics from /proc/meminfo.

Using these commands, you can easily check the available swap space and monitor its usage on your Linux server.