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 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 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 render-
	      ing 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 standard 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 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 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 periodically.

       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 jargon).   Don't  use  a
	      name  (including that of a spouse, parent, child, pet, fantasy character, famous person, and location) or any variation of your per-
	      sonal or account name.  Don't use accessible information about you (such as your phone number, 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 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 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)