Wikipedia - Paging

Create a swapfile with blocksize 1024 and 2GB

dd if=/dev/zero of=/swap/swapfile bs=1024 count=2M

Format the file and set permissions

mkswap /swap/swapfile
chown root:root /swap/swapfile
chmod 600 /swap/swapfile

Add the swapfile to swap

swapon /swap/swapfile

List the swapfiles

swapon -s

Turn off the swapfile (used swap will be moved to other swap or memory, might take a while)

swapoff /swap/swapfile