Since I'm lazy and not really a sysadmin full-time, I'm cheating by using the unattended-upgrades package. Here is how you do it:
- Install unattended-upgrades
- Add the following to /etc/apt/apt.conf
- See if you need to modify
- Watch your logs for any errors during updates (I use logcheck for this)
- Read the additional info at https://wiki.ubuntu.com/AutomaticUpdates for more details about this feature if you want to.