How to Add Swap Space in CentOS 7: A Step-by-Step Guide

dd if=/dev/zero of=/swapfile count=4096 bs=1MiB
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile

swapon -s

free -h 

echo /swapfile   swap    swap    sw  0   0 >> /etc/fstab