How do I setup a swap file in Linux?

cd <path to the swap file's directory>
dd if=/dev/zero of=swap bs=1024 count=32M
chmod 600 swap
mkswap swap
swapon swap
echo "<path to the swap file's directory>/swap none swap sw 0 0" | sudo tee -a /etc/fstab
swapoff swap
swapon -va

askubuntu.com/a/796997