Ubuntu: Enable swap

Ubuntu-swap.md

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

sudo fallocate -l 4G /swapfile
# verify
ls -lh /swapfile
#secure
sudo chmod 600 /swapfile
# setup
sudo mkswap /swapfile
# enable 
sudo swapon /swapfile
# verify
sudo swapon -s

# check memory
free -m

# check disk
df -h