Software Updater requires installation of untrusted packages from unauthenticated sources

Question

I use Ubuntu 14.04 Desktop Edition.
Now I see Software Updater's message that it must be updated. Then I get a message

requires installation of untrusted packages from unauthenticated sources

What's going on here? How can I solve it?

Answer 1

Open terminal and run these commands

sudo apt-get clean
cd /var/lib/apt
sudo mv lists lists.old
sudo mkdir -p lists/partial
sudo apt-get clean
sudo apt-get update

reference