When dual booting Ubuntu with other operating systems (Windows, Linux-based system, etc.), you may want to change which operating system to start by default. Ubuntu uses the GRUB boot loader for managing installed operating systems. To bring up the Grub boot screen, hold down the SHIFT key while your computer is starting up.
In this guide, we will help you change the default operating system using StartUp-Manager, which is an application with GUI for configuring Grub settings. Using this application will help you avoid the hassle of editing manually the /etc/default/grub file.
To isntall StartUp-Manager on Ubuntu 11.10/11.04, open the terminal (Ctrl+Alt+T) and run this command:
sudo apt-get install startupmanager
You can then start the application using the Unity dash:
Under "Default operating system", select the operating system you want to boot it by default from the dropdown menu, then click Close: