If you just forget the general password, you can update a new password by just inputting command passwd username under root identity.

If you forgot the password of super user, you can enter the system by using single user mode to boot computer to running level 1 as well as restarting the computer.

Use the following steps to boot single user mode:

1. Choose the kernel`s version that you want to boot in GRUB boot menu, such as Red Flag Advanced Server. (if you`ve already configured GRUB password, key in p and input the password)

2. Key in a, enter the edit mode, press <space> after ro root=LABEL=/, and then key in single.

3. Press <Enter>, system will start to boot, and enter the single user mode.

4. Under the prompt shell, use command passwd root to set new root password.