Forget Ubunto login password

What to do when you forget the login password in Ubuntu

Root privilege is required to reset the password. But in generally, Ubuntu not allow you to login as a root. You can use recovery boot to get the root privilege using the following steps.

1. Reboot the computer.
2. In Grub boot menu, press "e" key. If the menu was not show defaultly, press "ESC" when booting will go to Grub boot menu if your system is pre 9.10 or hold "SHIFT" key when booting will invoke the menu if the system is 9.10 or after.
3. In boot menu, select recovery mode.
4. After boot up, it will show some options, select "root prompt"
5. Now you will get a shell with root privilege, use passwd "username" to reset the password.