How to change the default OS Entry on Ubuntu 9.10 - Karmic Koala

Grub2, the new boot menu installed by default with Ubuntu 9.10

Ubuntu 9.10 ships with the new GRUB (Grand Unified Boot Loader 1.97 beta) in plain words its the software that boots the operating system you choose when you boot the computer. In earlier versions of Ubuntu / Grub to change the menu on the grub screen, one had to edit the /boot/grub/menu.lst file. In the new system this a little different from just editing the one file. 

1. First be root sudo su
2. Edit the file /etc/default/grub
3. Change the GRUB_DEFAULT value to number your default operating system
1. in My case
2. 0. Linux kernel ******
3. 1. Linux Recovery ****
4. 2. Memory Test bla bla...
5. 3. Memory Test bla bla bla...
6. 4. Windows 7 Loader....
4. I have set GRUB_DEFAULT = 4 for Windows 7
   
5. Change GRUB_TIMEOUT to change the default timeout if you want to. 
6. Run update-grub

-- output -- like

Generating grub.cfg ...
Found linux image: /boot/vmlinuz-2.6.31-14-generic
Found initrd image: /boot/initrd.img-2.6.31-14-generic
Found memtest86+ image: /boot/memtest86+.bin
Found Microsoft Windows XP Home Edition on /dev/sda1

done

You can verify your default boot entry changed or not by viewing the following file 

sudo cat /boot/grub/grub.cfg 



It showed set default="4" to me for my case .
Enjoy !!!