Comment # 1 on bug 1225932 from Thorsten Kukuk

(In reply to Robert Simai from comment #0)

> I'm not sure why refreshing the updates requires sudo as a regular user
> could successfully run "zypper lu" as well. But if it does, we could at
> least come up with a clearer message "switch to administrative access first"
> or such.

"zypper lu" uses the cache, so will show the results from the time when the
last refresh did run.

"zypper ref" needs write access to the cache, which only root has. Else it
cannot store the refreshed data, and maybe even not read necessary passwords to
access repositories.

So if "zypper lu" should give you current results and not from the cache, it
needs to run as root, too.