[Ubuntu] Reset root password!

Today, I found that one of PCs in the Math Department ICT room was installed "Ubuntu".

So, I tried to use it as I could. But I got a problem, I had no password for the root login.
I couldn't do anything if I had no root password.

Notice: If you're the linux user and you forget your root password, you won't able to do anything.

The internet is still useful, I could access to the internet. So I type "Reset Ubuntu root password"
in Google and then I found the solution.

Now, I've reseted the root password and changed it, so this computer is mind now.

Here's the solution.

1. Boot in Recovery Mode (Single-boot, just hold the shift key. Dual-boot, just press ESC key.)

2. When the menu is shown up, select "rootnetwork..."

3. Type "ls /home", the list of users in this PC will be shown up.
4. Suppose that I want to reset the password of user named "ackmin", I type "passwd ackmin".

5. After you type "passwd ....", the system will ask the new password, and you just type the new one
you want.

6. Then type "exit"

7. Reboot!