Hello Linux Geeksters.

In this article I will show you how to fix the Ubuntu 13.04 asks for update to Ubuntu 13.04 Error.
Error message:
"New release '13.04' available.
Run 'do-release-upgrade' to upgrade to it."
But I am already using Ubuntu 13.04 Raring Ringtail.
The fix:
$ sudo rm /var/lib/ubuntu-release-upgrader/release-upgrade-available
Explanation:
So, there is something wrong with: /etc/update-motd.d/91-release-upgrade
The /etc/update-motd.d/91-release-upgrade file calls /usr/lib/ubuntu-release-upgrader/release-upgrade-motd and checks if the /var/lib/ubuntu-release-upgrader/release-upgrade-available file exists.
If the /var/lib/ubuntu-release-upgrader/release-upgrade-available file is found, it goes to motd. If the release-upgrade-available file is not found, it calls /usr/lib/ubuntu-release-upgrader/check-new-release.
After the upgrade, the file /var/lib/ubuntu-release-upgrader/release-upgrade-available should be deleted. If it is not deleted, it gives you this error. To fix it, remove the file by hand.
$ sudo rm /var/lib/ubuntu-release-upgrader/release-upgrade-available