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PASSWD(1)				  User utilities				PASSWD(1)

NAME
       passwd - update user's authentication tokens

SYNOPSIS
       passwd [-k] [-l] [-u [-f]] [-d] [-e] [-n mindays] [-x maxdays] [-w warndays] [-i inactive-
       days] [-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 service 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 function 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 prefixing 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 stan-
	      dard input, which can be a pipe.

       -u, --unlock
	      This is the reverse of the -l option - it  will  unlock  the  account  password  by
	      removing	the  !	prefix.  This option is available to root only. By default passwd
	      will refuse to create a passwordless account (it will not unlock	an  account  that
	      has only "!" as a password). The force option -f will override this protection.

       -d, --delete
	      This  is	a  quick  way  to delete a password for an account. It will set the named
	      account passwordless. Available to root only.

       -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 sup-
	      ports password lifetimes.  Available to root only.

       -x, --maximum DAYS
	      This will set the maximum password lifetime, in days, if the  user's  account  sup-
	      ports 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  dis-
	      abled, 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 controlled 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 your password.  Use the password for a limited time and change  it  periodi-
	      cally.

       Choose a hard-to-guess password.
	      passwd  through  the  calls  to the pam_cracklib PAM module will try to prevent you
	      from choosing a really bad password, but it isn't foolproof; create  your  password
	      wisely.	Don't  use  something you'd find in a dictionary (in any language or jar-
	      gon).  Don't use a name (including that of a spouse, parent,  child,  pet,  fantasy
	      character,  famous  person,  and	location)  or  any  variation of your personal or
	      account name.  Don't use accessible information about you (such as your phone  num-
	      ber,  license  plate,  or social security number) or your environment.  Don't use a
	      birthday or a 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 mix-
	      ture 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 understandable 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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