How Often Should I Update Ubuntu?
Contents in Your Case You Would Want to Run Apt-Get Update After Adding a Ppa. Ubuntu Automatically Checks for Updates Either Every Week or as You Configure...
In your case you would want to run apt-get update after adding a PPA. Ubuntu automatically checks for updates either every week or as you configure it. It, when updates are available, shows a nice little GUI that lets you choose the updates to install, and then downloads/installs the selected ones.
How often should I run apt-get upgrade?
I would run apt-get update; apt-get upgrade at least weekly in order to get any security patches. You should get little no upgrades on 14.04 that aren’t security related at this point if you only have the default repos setup. I wouldn’t bother setting up a cron job; just run the commands once every few days.
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Should you update Ubuntu?
If you are running a machine that is vital to workflow, and needs to absolutely never ever ever have any chance of anything going wrong (i.e. a server) then no, don’t install every update. But if you are like most normal users, that are using Ubuntu as a desktop OS, yes, install every update as soon as you get them.