A change the way Ubuntu 9.04 notifies you of updates
A change to the Update Manager in Ubuntu 9.04 (Jaunty Jackalope) makes it to where you are no longer notified about software updates in the system tray on a daily basis. In Ubuntu 8.10 you were notified on a daily basis of any software updates. In 9.04 you will be notified on a daily basis if there are security updates, however, you will only be notified on a weekly basis for non security updates.
Ubuntu 9.04 introduces a change to the handling of package updates, launching update-manager directly instead of displaying a notification icon in the GNOME panel. Users will still be notified of security updates on a daily basis, but for updates that are not security-related, users will only be prompted once a week.
Users who wish to continue receiving update notifications in the previous manner can restore the earlier behavior using the following command (in the terminal window):