Dear Friends,
I am trying to install new filles, but I can't, and I can't loging me as a super-user. Perhaps I forget my password, yet I did not think so.
But, can I get a new password of super-user?
Following, some copyes of the Shell - Konsole:
knoppix@kalango:~$ apt-get install tux
E: Não foi possível abri arquivo de trava /var/lib/dpkg/lock - open (13 Permission denied)
E: Unable to lock the administration directory (/var/lib/dpkg/), [B]are you root?
(...)

knoppix@kalango:~$ su *****
Unknown id: *****
(...)
knoppix@kalango:~$ sudo su *****
Unknown id: ********
(...)
knoppix@kalango:~$ su
Password:
su: Authentication failure
Sorry.
knoppix@kalango:~$ su
Password:

(At this moment, I used the commom password. In other moments, I tryed to log me in with it, but I can't log, but using "su" without other arguments, it was possible).
Thank you.

to change passwords you use the command passwd *user*

example:

I've might misunderstood you, but you are not supposed to write the password as a part of the command, you will be asked for the password.

when you use sudo, you have been privileged with superuser abilities, and therefor use your own password as authentication, while su changes user to root, and therefor you will have to use the root password for authentication.

Boot from any live-cd and open a /etc/shadow file of your installed system. There are entries of type <username>:<password_hash>:...etc in it (complete format in man shadow).
Find root entry (usually it's first) and replace the password hash with a hash of your regular user entry.
Than boot into installed system, login as a root with your regular user's password, and change root pass with passwd command.

Thank you, but how can I write a hash of my regular user entry, that is, how can I write such a hash?

I think the assumption was that you could find the hashed password on another line of that same file for some account for which you know the unhashed password. Then edit the file to make the hashed password of root the same as the hashed password for the other account for which you know the unhashed password.

Dear friends and fellow users,
Thanks because you was so careful.
I follow the counsel of Samotnik. It was very instructive. I saw the shadow directly, I know what is criptography, and I learn a lot of commands and know a lot of archives, or command "Kuser", as described at the KDE/SYSTEM/KUSER, and I received a temporaly (?) login, and by it I edit the user by de "Kuser" graphic. But I didn't believe it immediatly On the contrary, I continued to try to edit the shadow, until a half past four AM. As I sayd, it was instructive, but I became tired.
At this day, I try many passwords, then I try the password that I edit yesterday (or, better, today) and I became root.
Thanks to all of you, and I give thanks also to God, who use all things to discipline and perfect me in His life.