Automate Linux Swap File Creation and Removal with Simple Shell Scripts

How to Check Current Swap Size

Use the free -h command to view memory usage and swapon --show to list active swap devices. The example output shows a 2 GB swap partition currently in use.

Creating a Swap File

Create a file named create_swap.sh with the following content and give it execute permission.

$ nano create_swap.sh
#!/bin/sh

# size of swapfile in megabytes
swapsize=1024

# does the swap file already exist?
grep -q "swapfile" /etc/fstab

# if not then create it
if [ $? -ne 0 ]; then
    echo 'swapfile not found. Adding swapfile.'
    fallocate -l ${swapsize}M /swapfile
    chmod 600 /swapfile
    mkswap /swapfile
    swapon /swapfile
    echo '/swapfile none swap defaults 0 0' >> /etc/fstab
else
    echo 'swapfile found. No changes made.'
fi

echo '--------------------------------------------'
echo 'Check whether the swap space created or not?'
echo '--------------------------------------------'
swapon --show

Make the script executable: $ sudo chmod +x create_swap.sh Run it to create and mount the 1 GB swap file:

$ sudo ./create_swap.sh

swapfile not found. Adding swapfile.
Setting up swapspace version 1, size = 1024 MiB (1073737728 bytes)
...
NAME      TYPE   SIZE   USED PRIO
/dev/sda5 partition 2G 954.1M -1
/swapfile file      1024M 0B   -2

After execution, the new swap file appears in the list. Reboot to ensure it is used.

Removing a Swap File

Create a script named remove_swap.sh with the following content and make it executable.

$ nano remove_swap.sh
#!/bin/sh

# does the swap file exist?
grep -q "swapfile" /etc/fstab

# if it does then remove it
if [ $? -eq 0 ]; then
    echo 'swapfile found. Removing swapfile.'
    sed -i '/swapfile/d' /etc/fstab
    echo "3" > /proc/sys/vm/drop_caches
    swapoff -a
    rm -f /swapfile
else
    echo 'No swapfile found. No changes made.'
fi

echo '--------------------------------------------'
echo 'Check whether the swap space removed or not?'
echo '--------------------------------------------'
swapon --show

Give the script execute permission: $ sudo chmod +x remove_swap.sh Run it to remove and unload the swap file:

$ sudo ./remove_swap.sh

swapfile found. Removing swapfile.
swapoff: /dev/sda5: swapoff failed: Cannot allocate memory
--------------------------------------------
Check whether the swap space removed or not?
--------------------------------------------
NAME      TYPE   SIZE   USED PRIO
/dev/sda5 partition 2G 951.8M -1

The swap file entry disappears from the output, confirming its removal.

Summary

These two concise shell scripts automate the otherwise manual steps of creating, mounting, and later removing a Linux swap file, allowing you to adjust swap size and filename by editing a few variables.