How to Create Swap File in Linux

Swap is space on a disk that is reserved to be used as virtual memory. When a Linux server runs out of memory, the kernel can move the processes into swap to make room for other processes in the main memory. swap can be extended using swap file and swap partition

Follow Below Steps To Add a Swap File in Linux

We can use the dd command to create swap file and The mkswap command to set up a Linux swap area .

Create Swap File

Type the following command to create 512MB swap file :
# dd if=/dev/zero of=/swapfile bs=512M count=1

Set Up a Linux Swap

Type the following command to set up a Linux swap area in a file:
# mkswap /swapfile or Use -f to force

Now activate /swapfile swap space:
# swapon /swapfile

Make an entry in /etc/fstab file to mount permanently

Add Below entry to /etc/fstab file:
# vi /etc/fstab
Append the following line:
/swapfile swap swap defaults 0 0

Run below command to update the swap space

#swapon -a

How to verify Swap is activated or Not?

Simply use the free command:
# free -m
# swapon -s