The root user has full administrative access on Linux systems, but Ubuntu uses sudo instead of root for security. Sudo allows users to run commands with root privileges by entering their own password. The first user account created during installation gets sudo access by default. Users can use sudo before commands in the terminal. Sudo remembers passwords for a time to avoid frequent re-entry. The root password can be changed or disabled using sudo passwd. Users without the root password can still access root using sudo -i and entering their own password. The root password can also be reset in recovery mode.

2. ROOT & SUDO
The root user in GNU/Linux is the user which has
administrative access to your system. Normal
users do not have this access for security
reasons. However, Ubuntu does not include the
root user. Instead, administrative access is
given to individual users, who may use the
"sudo" application to perform administrative
tasks. The first user account you created on
your system during installation will, by default,
have access to sudo. You can restrict and
enable sudo access to users with the Users

3. When you run an application that requires root
privileges, sudo will ask you to input your
normal user password. This ensures that rogue
applications cannot damage your system, and
serves as a reminder that you are about to
perform administrative actions which require
you to be careful!
To use sudo when using the command line,
simply type "sudo" before the command you
wish to run. Sudo will then prompt you for your
password.
Sudo will remember your password for a set
amount of time. This feature was designed to

4. To change the password via terminal

$sudo passwd root

Enter the new password and Retype the
password to confirm.
To disable password

If you don't want password to authenticate while
application installation, login......

$sudo passwd -I root

5. While you are working as user, you need to
access the root, but you dono the root
password, just type

$sudo -i

Enter your user password and start work as
root.

6. Root Passwd Reset

You forget the root password, you need to login
as root.

To do this you have to reset or change the
password.

7. 
First, you have to reboot into recovery mode.

If you have a single-boot (Ubuntu is the only
operating system on your computer), to get the
boot menu to show, you have to hold down the
Shift key during bootup.

If you have a dual-boot (Ubuntu is installed next
to Windows, another Linux operating system, or
Mac OS X; and you choose at boot time which
operating system to boot into), the boot menu
should appear without the need to hold down
the Shift key.

For older versions of Ubuntu (9.04 and 8.04),
you can press the Escape key during bootup in

8. 
From the boot menu, select recovery mode,
which is usually the second boot option.

10. 
After you select recovery mode and wait for all
the boot-up processes to finish, you'll be
presented with a few options. In this case, you
want the Drop to root shell prompt option so
press the Down arrow to get to that option, and
then press Enter to select it.

12. 
The root account is the ultimate administrator
and can do anything to the Ubuntu installation
(including erase it), so please be careful with
what commands you enter in the root terminal.

Once you're at the root shell prompt, if you
have forgotten your username as well, type

$ls /home

That's a lowercase L, by the way, not a capital i,
in ls. You should then see a list of the users on
your Ubuntu installation. In this case, I'm going
to reset ckuser18 password.

13. To reset the password, type

$passwd username
where username is the username you want to
reset. In this case, I want to reset ckuser's
password, so I type

$passwd ckuser18
You'll then be prompted for a new password.
When you type the password you will get no
visual response acknowledging your typing.
Your password is still being accepted. Just type
the password and hit Enter when you're done.
You'll be prompted to retype the password. Do

14. After you get back to the recovery
menu, select resume normal boot

15. Now you can login as root because you know the
password.

16. HACK-ROOT ACCESS

1. You need to reboot your Ubuntu

2. When you reach GRUB page, press ‘e’
(without quotes), this command is to edit grub

3. Edit one of your boot command

4. Replace “ro qiuet splash” by “rw
init=/bin/bash” at the end.

5. Press “ctrl x” or “b”, this will make your
Ubuntu to boot with passwordless root shell,ie
you will be logined as root without password.

6. Then just change your password with