Update manger do not provide option to upgrade. It displays "Your system is up-to-date" instead. I tried Check button many times but received same message. Please help.
NOTE: Specific to upgrade of 11.10 to 12.04 (and not from 10.04 LTS)
From: ubuntu.com - UbuntuDesktop - Upgrading - GUI method
Upgrading from Ubuntu 11.10
To upgrade from Ubuntu 11.10 on a desktop system, start "Update Manager". It should display the following message: "New distribution release '12.04' is available. Click Upgrade and follow the on-screen instructions".
I can confirm this works on my Ubuntu 11.10 desktop.
From: ubuntu.com - UbuntuServer - Upgrading - command-line method
From 11.10 to 12.04
To upgrade from Ubuntu 11.10 on a server system, follow the steps listed below:
Install the update-manager-core package (if it is not already installed).
Run sudo do-release-upgrade to launch the upgrade tool. Follow the on-screen instructions. Note that the server upgrade is now more robust and will utilize GNU screen and automatically re-attach in case of dropped connection problems, for example.
So, type the following commands:
sudo apt-get install update-manager-core sudo do-release-upgrade sudo apt-get update && sudo apt-get upgrade
I had to do an apt-get purge update-manager-core and the install update-manager-core before do-release-upgrade would recognize any new releases for 11.10.