Problem in changing password

[Jacques B.]

On 10/9/07, Frank Cox <theatre at sasktel.net> wrote:
> On Tue, 09 Oct 2007 16:24:51 +0200
> mostafa <mostafaradwan at gmail.com> wrote:
>
> > passwd: User not known to the underlying authentication module
>

Did you check out
http://www.linuxquestions.org/questions/linux-general-1/passwd-user-not-known-to-the-underlying-authentication-module-83380/

or
http://lists.alioth.debian.org/pipermail/debian-live-devel/2006-May/000249.html

or

http://www.wains.be/index.php/2007/02/19/passwd-user-not-known-to-the-underlying-authentication-module/

and many more by doing a Google search of your error.

Your solution may already exist out there.  Might be better than
seeking to have someone re-trouble shoot something that may have
already been trouble shot and posted online.

I note that you didn't log in as root but rather did a su - to root.
Try one of the other terminal windows (CTRL-ALT F1-F6) and log in as
root from one of those and try to change it. See if that makes a
difference.

Jacques B.