You will be in the big trouble when dis-remember the root password. Only way to recover forgotten root password is to boot the server in single user mode to change the root password.

Here is practical way of doing it.

1.    Reboot the server with following combination when the system asks for username & password in the console.
alt + ctrl + del

2.    Then system get rebooted and comes at boot loader screen now press “space” bar.

3.    On the boot menu it will show the OS details of the respective server.

4.    Now select the Linux (in this case red hat Enterprise Linux 2.6.32)

5.    Now enter into the OS boot menu by pressing “e” option which stands for edit.

6.    Now select Kernel parameter entry which is second entry in above boot menu & press “e” to make change & write “s” at the end of the line to boot the system in the single user-mode and press enter. As below:

7.    Now system again comes at the boot selection menu as describe in the step 5 & press b to boot the system finally.
8.     When the system comes at the command prompt change the password for root.

9.    And reboot the system using reboot command.