Create swap file in Linux

Before creating a swap file, we should check the size of the current swap:

#cat /proc/meminfo | grep SwapTotal
SwapTotal: 9233400 kB

Create a swap file

To create swap file, you will need to use dd command:

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

if=/dev/zero - read from /dev/zero
of=/newswap -  write to /newswap
bs=1024 - blocksize in bytes for reading and writing
count=1048576 - swap file size

Create swap area

Type the following command to set up a Linux swap area in a file.

#mkswap /newswap

Set permissions for the file, so only the root user can use it:

#chmod 0600 /newswap
#chown root:root /newswap

Acticate swap

Next, we should activate the swap file:

#swapon /newswap

At the end, we want the new swap file to be active after reboot and we should add it in fstab file:

#nano /etc/fstab

add the following line at the end of the file:

/newswap swap swap defaults 0 0

Now check if swap is activated or not:

#cat /proc/meminfo | grep SwapTotal

or

#free -m