Some systems do not ship with swap partition. A swap file is used instead.
dd if=/dev/zero of=/swapfile bs=1M count=1024
mkswap -f /swapfile
chown root:root /swapfile
chmod 0600 /swapfile
Also put swapon /swapfile in /etc/rc.local. In this way, swap will be turned on later but without modifying /etc/fstab.