If you have only one package, you will land on the Administration page. If you have more than one package, select the package in question to reach its Administration page.
Click the Server Re-image link from the 1&1 Servers panel.
Click Server Re-image
In the text box, enter the root user password that should be set for the new operating system install. Next, choose the operating system image to install and click the Next button.
Choose a password and select an operating system to install
Read over the disclaimer on the page for more information and double-check the root user password entered to ensure it is correct. If no changes are necessary, click the Initialize button to begin the re-image.
Click the Initialize button
You are informed the re-image is starting and the server should be available within 1-1.5 hours. Click the Go To Overview button to return to the administration section of the 1&1 Control Panel.
Click the Go To Overview button
For additional information, you may want to reference: