How to Add Swap Space on CentOS 8

add-swap.sh

#!/bin/bash
# Make swap space
# ----------------
# How to use?
# Create add-swap.sh file with this content
# chmod +x add-swap.sh
# Run: ./add-swap.sh

if [[ $EUID -ne 0 ]]; then
   echo "Please execute script with a superuser..." 1>&2
   exit 1
fi

SWAP_PATH=/swapfile

# DEBUG
#rm -rf $SWAP_PATH

if test -f "$SWAP_PATH"; then
    echo "$SWAP_PATH exists."
    exit 1
fi

echo "Start create Swap Space to $SWAP_PATH"

#============================================

echo "Tell me size for Swap Space."
echo "Use Gigabyte unit. Ex: enter 4 for 4G"
until [[ $SWAP_SIZE =~ ^[0-9]+$ ]]; do
   read -rp "Swap size: " -e SWAP_SIZE
done

SWAP_UNIT_SHORT="G"
SWAP_UNIT="GB"
echo "Create $SWAP_PATH with size: $SWAP_SIZE$SWAP_UNIT"

#============================================

FALLOCATE_CMD=$(fallocate -l $SWAP_SIZE$SWAP_UNIT_SHORT /swapfile)
if [[ -z "$FALLOCATE_CMD" ]]; then
    dd if=/dev/zero of=$SWAP_PATH bs=1024 count=$((1024 * 1024 * $SWAP_SIZE))
fi

#===========================================

chmod 600 $SWAP_PATH
mkswap $SWAP_PATH
swapon $SWAP_PATH
swapon --show
free -m

#===========================================

echo "Set swap piness to 15"

sysctl vm.swappiness=15
echo "vm.swappiness=15" >> /etc/sysctl.conf
echo ""
echo "=========== DONE ============"
echo ""
#==========================================

echo "NOTE:"
echo "Manual add swap start with startup to /etc/fstab"
echo "$SWAP_PATH swap swap defaults 0 0"
echo ""

echo "For removing Swap"
echo "swapoff -v $SWAP_PATH"
echo "rm -rf $SWAP_PATH"
echo ""