Linux uses Swap Space to back its physical memory with an overflow area. In most cases the suggested amount is a disk space equal to the amount of physical memory you have installed. You don’t want your system to ever run out of RAM+swap, but you usually would rather have enough RAM in the system. So twice the size of RAM doesn’t need to swap.

The free -m command shows that the swap memory in your current server.

We can increase 4GB of swap size now.

Create Swap file

touch /swapfile

Use the following command to create 4GB of swap file.

# dd if=/dev/zero of=/swapfile bs=1M count=4096

if=/dev/zero : Read from /dev/zero file. /dev/zero is a special file in that provides as many null characters to build storage file called /swapfile.
of=/swapfile1 : Read from /dev/zero write stoage file to /swapfile.
bs=1M : Read and write 1M at a time.
count=4096 : Copy only 4096 input blocks.
This will create a new partition with 4GB space. To make it a swap partition you need to execute the following command.

# mkswap /swapfile

Now the swap file is created.

activate /swapfile file swap space now.

# swapon /swapfile

Add entry on /etc/fstab file to activate after Linux system reboot.

# vi /etc/fstab

/swapfile swap    swap    defaults        0 0

save and close the file.

Now check your swap space now.

# free -m

In order to delete swap.

Run “swapoff /swapfile” command

Remove the entry from /etc/fstab file

Remove /swapfile  file (using rm command)