Upgrade Ubuntu 16.10 to Ubuntu 17.04 Desktop
To upgrade on a desktop system:
Open the "Software & Updates" Setting in System Settings.
Select the 3rd Tab called "Updates".
Set the "Notify me of a new Ubuntu version" dropdown menu to "For any new version".
Press Alt+F2 and type in "update-manager -c" (without the quotes) into the command box.
Update Manager should open up and tell you: New distribution release ‘17.04' is available.
If not you can also use "/usr/lib/ubuntu-release-upgrader/check-new-release-gtk"
Click Upgrade and follow the on-screen instructions.
Upgrade Ubuntu 16.10 to Ubuntu 17.04 Server
To upgrade on a server system:
Install the update-manager-core package if it is not already installed.
Make sure the Prompt line in /etc/update-manager/release-upgrades is set to normal.
Launch the upgrade tool with the command sudo do-release-upgrade.
Follow the on-screen instructions.