Linux Add a Swap File – Howto

Procedure To Add a Swap File Under Linux

You need to use the dd command to create swap file. The mkswap command is used to set up a Linux swap area on a device or in a file.

Step #1: Login as the Root User

Login to remote server using the ssh client. Switch to the root user by typing su – and entering the root password, when prompted

Step #2: Create Storage File

Type the following command to create 1GB swap file (1024 * 1024MB = 1048576 block size):

# dd if=/dev/zero of=/swapfile1 bs=1024 count=1048576

Step #3: Set Up a Linux Swap Area

Type the following command to set up a Linux swap area in a file:
# mkswap /swapfile1

Setup correct file permission for security reasons, enter:
# chown root:root /swapfile1
# chmod 0600 /swapfile1

Finally, activate /swapfile1 swap space immediately, enter:
# swapon /swapfile1

To activate /swapfile1 after Linux system reboot, add entry to /etc/fstab file. Open this file using a text editor such as vi:
# vi /etc/fstab

Append the following line:
/swapfile1 swap swap defaults 0 0
Save and close the file. Next time Linux comes up after reboot, it enables the new swap file for you automatically.

How do I Verify Swap is Activated or Not?

Simply use the free command:
$ free -m