#First, create a file which will be used as swap space
#With non Centos
sudo fallocate -l 1G /swapfile
# With Centos
sudo dd if=/dev/zero of=/swapfile bs=2048 count=1048576

#Ensure that only the root user can read and write the swap file:
sudo chmod 600 /swapfile

#set up a Linux swap area on the file
sudo mkswap /swapfile

#activate the swap
sudo swapon /swapfile

#Make the change permanent by opening the /etc/fstab file
sudo nano /etc/fstab

#and pasting the following line:
/swapfile swap swap defaults 0 0

#Verify
sudo swapon --show