Create and activate a swapfile

createswap.sh

#!/bin/sh
# Create and activate swapfile

NOW=$(date '+%Y%m%d%H%M%S')
SWAPSIZEGB=6
SWAPFILENAME="/swap.${NOW}.img"

if [ "$(id -u)" != "0" ]; then
    echo "This script must be run as root (sudo)" 1>&2
    exit 1
fi

if [ -f "${SWAPFILENAME}" ];then
    echo "${SWAPFILENAME} already exists"
    exit 2
fi

if ! [ ${SWAPSIZEGB} -eq ${SWAPSIZEGB} ] 2> /dev/null ;then
    echo "SWAPSIZEGB must be an integer"
    exit 3
fi

SWAPINBYTES=$(expr ${SWAPSIZEGB} \* 1048596)
echo "creating swap space"
dd if=/dev/zero of="${SWAPFILENAME}" bs=1024 count=${SWAPINBYTES}
chmod 0600 "${SWAPFILENAME}"
mkswap "${SWAPFILENAME}"
swapon "${SWAPFILENAME}"
cp /etc/fstab "/etc/fstab.${NOW}.bak"
echo "${SWAPFILENAME} none swap sw 0 0" | sudo tee -a /etc/fstab
echo "${SWAPSIZEGB} GB swap file created at ${SWAPFILENAME}"
free