Comment 8 for bug 746508

Can confirm this happens on "apt-get update" command on Kubuntu 16.04. If I have more processes open when I try to run this it makes my computer unresponsive, not only because the processor is at 100% which is bad enough, but because it will start digging into swap, and I have 16GB of RAM. Terrible bug indeed!

Interestingly enough if I run "apt-get install update-notifier" it would appear as if it where not installed so it's all the more frustrating.

For those that have problems with their computer being unusable from time to time there is a file in cron.daily and cron.weekly that starts this process automatically which you can comment out. Or if you want to disable it completely you can just:

mv /usr/lib/update-notifier/apt-check /usr/lib/update-notifier/apt-check.disabled
touch apt-check
chmod 777 $_

I'm not really sure what the above would break but it's better than having the system unusable in my opinion.