Login as a root from GUI for Ubuntu 8.10

1.Login as a user from GUI.
2.Now Click on System -> Click on Administration -> Click on Users and Groups.

3. You will see the root user is locked. so Click on UNLOCK button it will ask you password of your user.Enter password and click on OK.
4.You will able to see now user root is now unlocked,
Double-Click on root and set your root password. Then Click OK. Close the Users and Groups window now.

Applications -> Accessories -> Terminal.

6.Login as a root from terminal by executing su – root command enter password and login from root.
7.Make a back-up of your /etc/gdm/gdm.conf file by executing this command

cp /etc/gdm/gdm.conf /etc/gdm/gdm.conf.backup

8.Open your /etc/gdm/gdm.conf file in your favorite browser
vim /etc/gdm/gdm.conf
9.Search for AllowRoot=false and Replace it with AllowRoot=true.(remember this is case sensitive).
10.Now Log out from current user and Login as a root with password which you set earlier.

[N.B. Be careful about root user. its very sensitive for your os. try to use your linux operating system as normal user. when you need to do any changes then you can use "su -" command for getting the privilage of root user. thanks]