If you want to have a root on linux machine, but you don't know how?
It is possible but only then if there is no grub menu encrypted, if not we are able to have a root access.

First of all we need to have access to grub menu (You may see it when u have different OS on one computer or at least a few kernels).
(how much it should wait until one of the OS's should start).

When you see grub menu timer, just stop it ( narrow buttons or smthing like that )
So we stopped grub menu timer
Look at the image ( took it from google )

So we need to choose the system we want to access with root privileges ( holy grenade this is exciting, and someone of the neighbours is smoking right now I can feel it )
So yeah press "e" key on your keyboard..and now we can see (boot) properties. Choose second line which starts from kernel /vmlinuz.....
Press "e" again and go to end of this statement.
Now press "space" and type:
single linux
Now press Enter button and then press "b" key.
yeeeahhhh here it goes

[root@computername] #

After that u may add new user:
adduser r00t2
passwd r00t2
Or change old user password:
passwd olduser
Or change even root password:
Remember! Having access to other computer & espionage isn't so nice thing and prohibited by law.
Use this thing when u forgot ur password