Quick and easy script to setup swap

createswap.sh

#!/bin/sh
# createswap.sh
# creates swap file.
# Optionally specify size (e.g. 1024M)
# If no size is specified, default to physical memory / 4
#
# <ricky@rickyhewitt.me>

if [ $1 ]; then
    SWAP_SIZE=$1
else
    PHYSICAL_MEM=$(head /proc/meminfo | awk 'BEGIN {OFS = FS} NR==1{print $2}')
    SWAP_SIZE=$(($PHYSICAL_MEM/4))
fi

echo "Creating swap file with size of $SWAP_SIZE"

fallocate -l $SWAP_SIZE /swap
mkswap /swap
chmod 600 /swap
swapon /swap
sed -i -e '$a/swap   none    swap    sw    0   0' /etc/fstab
sysctl vm.swappiness=15
sed -i -e '$avm.swappiness=15' /etc/sysctl.conf