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passwd



SYNOPSIS

       passwd  [-k]  [-l]  [-u  [-f]]  [-d] [-e] [-n mindays] [-x maxdays] [-w
       warndays] [-i inactivedays] [-S] [--stdin] [username]


DESCRIPTION

       The passwd utility is used to update user's authentication token(s).

       This task is achieved through calls to the Linux-PAM and  Libuser  API.
       Essentially, it initializes itself as a "passwd" service with Linux-PAM
       and utilizes configured  password  modules  to  authenticate  and  then
       update a user's password.

       A simple entry in the global Linux-PAM configuration file for this ser-
       vice would be:

        #
        # passwd service entry that does strength checking of
        # a proposed password before updating it.
        #
        passwd password requisite pam_cracklib.so retry=3
        passwd password required pam_unix.so use_authtok
        #

       Note, other module types are not required for this application to func-
       tion correctly.


OPTIONS

       -k, --keep
              The option -k is used to indicate that the update should only be
              for expired authentication tokens (passwords); the  user  wishes
              to keep their non-expired tokens as before.

       -l, --lock
              This  option  is  used to lock the password of specified account
              and it is available to root only. The locking  is  performed  by
              rendering the encrypted password into an invalid string (by pre-
              fixing the encrypted string with an !). Note that the account is
              not  fully  locked - the user can still log in by other means of
              authentication such as the ssh public  key  authentication.  Use
              chage -E 0 user command instead for full account locking.

       --stdin
              This  option is used to indicate that passwd should read the new
              password from standard input, which can be a pipe.

       -e, --expire
              This is a quick way to expire a password  for  an  account.  The
              user will be forced to change the password during the next login
              attempt.  Available to root only.

       -f, --force
              Force the specified operation.

       -n, --minimum DAYS
              This will set the minimum password lifetime,  in  days,  if  the
              user's  account  supports password lifetimes.  Available to root
              only.

       -x, --maximum DAYS
              This will set the maximum password lifetime,  in  days,  if  the
              user's  account  supports password lifetimes.  Available to root
              only.

       -w, --warning DAYS
              This will set the number of days in advance the user will  begin
              receiving  warnings that her password will expire, if the user's
              account supports password lifetimes.  Available to root only.

       -i, --inactive DAYS
              This will set the number of  days  which  will  pass  before  an
              expired password for this account will be taken to mean that the
              account is inactive  and  should  be  disabled,  if  the  user's
              account supports password lifetimes.  Available to root only.

       -S, --status
              This  will  output  a  short information about the status of the
              password for a given account. Available to root user only.


Remember the following two principles

       Protect your password.
              Don't write down your password - memorize  it.   In  particular,
              don't write it down and leave it anywhere, and don't place it in
              an unencrypted file!  Use unrelated passwords for  systems  con-
              trolled  by  different  organizations.  Don't give or share your
              password, in particular to someone claiming to be from  computer
              support  or  a  vendor.   Don't  let anyone watch you enter your
              password.  Don't enter your password to  a  computer  you  don't
              trust or if things "look funny"; someone may be trying to hijack
              simple pattern (such as "qwerty", "abc", or "aaa").   Don't  use
              any  of  those  backwards, followed by a digit, or preceded by a
              digit. Instead, use a mixture of upper and lower  case  letters,
              as well as digits or punctuation.  When choosing a new password,
              make sure it's unrelated to  any  previous  password.  Use  long
              passwords  (say  at  least  8 characters long).  You might use a
              word pair with punctuation inserted,  a  passphrase  (an  under-
              standable  sequence  of words), or the first letter of each word
              in a passphrase.

       These principles are partially enforced by the system, but only  partly
       so.  Vigilance on your part will make the system much more secure.


EXIT CODE

       On  successful  completion  of its task, passwd will complete with exit
       code 0.  An exit code of 1 indicates an error occurred.  Textual errors
       are written to the standard error stream.


CONFORMING TO

       Linux-PAM (Pluggable Authentication modules for Linux).


FILES

       /etc/pam.d/passwd - the Linux-PAM configuration file


BUGS

       None known.


SEE ALSO

       pam(8), pam.d(5), libuser.conf(5), and pam_chauthtok(3).

       For more complete information on how to configure this application with
       Linux-PAM, see the Linux-PAM System Administrators' Guide.


AUTHOR

       Cristian Gafton <gafton@redhat.com>


GNU/Linux Jun 20 2012 PASSWD(1)



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