Linux Swap
# 1. generate an empty file
$ dd if=/dev/zero of=/var/swapfile bs=1M count=1024
# 2. format it as swap
$ mkswap /var/swapfile
# 3. turn on it
$ swapon /var/swapfile
# 4. make it works after boot
$ cat "/var/swapfile swap swap defaults 0 0" >> /etc/fstab