1. sudo fallocate -l 4G /swapfile

2. sudo chmod 600 /swapfile

3. sudo mkswap /swapfile

4. sudo swapon /swapfile

5. sudo swapon -s

6. free -m

7. sudo nano /etc/fstab

8. /swapfile none swap sw 0 0

https://www.digitalocean.com/community/tutorials/how-to-add-swap-on-ubuntu-14-04