Unattended Upgrades Ubuntu

First:  Install the unattended upgrade package

sudo apt-get install unattended-upgrades

Edit this file accordingly

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

Install the Update Notifier

apt-get install update-notifier-common

NOTE:
“If you want the script to automatically reboot when needed, you not only need to set Unattended-Upgrade::Automatic-Reboot "true", but you also need to have the “update-notifier-common” package installed. On minimal installations this is not installed by default and without it the automatic updater will never reboot and will not even tell you that you need to reboot manually if you have email notifications configured!

“The files in /etc/apt/apt.conf.d/ are evaluated in lexicographical order with each file capable of overriding values set in earlier files. This makes it insufficient to view the setting in /etc/apt/apt.conf.d/20auto-upgrades and why it is recommended to use apt-config.”

Resources
https://help.ubuntu.com/community/AutomaticSecurityUpdates
https://www.techrepublic.com/article/how-to-enable-automatic-security-updates-on-centos-7-with-yum-cron/