Change default operating system at boot

To change which operating system starts by default when the computer starts up, edit the grub configuration file.

1. Make a backup of the configuration file, and open it in a text editor:
   

   sudo cp /boot/grub/menu.lst /boot/grub/menu.lst_backup
   sudo gedit /boot/grub/menu.lst

2. Find this line:
   

   ...
   default 0
   ...

3. Replace with the following line:
   

   default X

   	You should replace X with a number, according to the order which your operating systems appear in the configuration file. You should start counting from 0. For example, if you wish the default operating system to be the first in the list, replace X with 0, if you wish the default operating system to be the second in the list, replace X with 1, and so on.

4. Save the edited file (an example)