OK, it *would* be possible to use cron to run a "apt-get update" as root, say every 30 minutes or so .. but here's the problem, it would lock the apt package cache whilst it was running the update, which would mean if you started a package manager it would throw an error.
If you want to add a cron job, open a terminal and run:
When nano displays in the terminal, use the down arrow key to move the cursor to the end of the file.
Add a new line that reads:-
*/30 * * * * apt-get update
Now to save the file and apply the changes hit Ctrl+X
then hit Y
then hit Enter
Now every 30 minutes the command apt-get update
will be run (as root) in the background .. the package cahe will be updated .. and mintudate should become aware of any new updates that are available.
Then email the Mint devs and ask them WTF they are playing at .. Clems response that mintupdate isn't supposed to be a real time update notifier doesn't make any sense at all, what'sd the point in the tray icon then ?
At best the tray icon always saying you're up to date will confuse new users .. at worst they'll listen to it and never apply updates.
Interesting thread on the topic here:http://forums.linuxmint.com/viewtopic.php?f=34&t=103740