A simple little shell script that executes the digital ocean swap file tutorial.

swap.sh

#/bin/sh

# Creates a 1gb swap image.
# @see https://www.digitalocean.com/community/tutorials/how-to-configure-virtual-memory-swap-file-on-a-vps

if [ -f /var/swap.img ]; then
	echo "Swap file already exists."
else
	touch /var/swap.img
	chmod 600 /var/swap.img
	dd if=/dev/zero of=/var/swap.img bs=1024k count=1000
	mkswap /var/swap.img
	swapon /var/swap.img
	echo "/var/swap.img    none    swap    sw    0    0" >> /etc/fstab
	sysctl -w vm.swappiness=30
	free
	echo "Swap created and added to /etc/fstab for boot up."
fi

Usage:

curl -o swap.sh https://gist.githubusercontent.com/peterchester/4537ed05a790045dd11f/raw/51121ac2d3a370e2c27032c9e14c0ca2bbf2b382/swap.sh
sudo /bin/sh swap.sh
rm -rf swap.sh

You may want to add this line not to lose swappiness after reboot:
echo "vm.swappiness=30" >> /etc/sysctl.conf