Ubuntu Auto Update

In recent clients, security updates are installed by default. You can run this again to be sure, however.

sudo apt-get install unattended-upgrades
sudo dpkg-reconfigure -plow unattended-upgrades

Alternatively, look at this file and enable additional channels if desired

sudo vim /etc/apt/apt.conf.d/50unattended-upgrades

Lastly, you may want a periodic reboot so kernel updates take affect

sudo vim /etc/crontab

 0 3 * * 7 root /sbin/shutdown -r +10 "Weekly reboot in 10 minutes"