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PASSWD(1)			 User Commands			     PASSWD(1)

NAME
       passwd -	change user password

SYNOPSIS
       passwd [options]	[LOGIN]

DESCRIPTION
       The passwd command changes passwords for	user accounts. A normal	user
       may only	change the password for	his/her	own account, while the
       superuser may change the	password for any account.  passwd also changes
       the account or associated password validity period.

   Password Changes
       The user	is first prompted for his/her old password, if one is present.
       This password is	then encrypted and compared against the	stored
       password. The user has only one chance to enter the correct password.
       The superuser is	permitted to bypass this step so that forgotten
       passwords may be	changed.

       After the password has been entered, password aging information is
       checked to see if the user is permitted to change the password at this
       time. If	not, passwd refuses to change the password and exits.

       The user	is then	prompted twice for a replacement password. The second
       entry is	compared against the first and both are	required to match in
       order for the password to be changed.

       Then, the password is tested for	complexity. As a general guideline,
       passwords should	consist	of 6 to	8 characters including one or more
       characters from each of the following sets:

       o   lower case alphabetics

       o   digits 0 thru 9

       o   punctuation marks

       Care must be taken not to include the system default erase or kill
       characters.  passwd will	reject any password which is not suitably
       complex.

   Hints for user passwords
       The security of a password depends upon the strength of the encryption
       algorithm and the size of the key space.	The legacy UNIX	System
       encryption method is based on the NBS DES algorithm. More recent
       methods are now recommended (see	ENCRYPT_METHOD). The size of the key
       space depends upon the randomness of the	password which is selected.

       Compromises in password security	normally result	from careless password
       selection or handling. For this reason, you should not select a
       password	which appears in a dictionary or which must be written down.
       The password should also	not be a proper	name, your license number,
       birth date, or street address. Any of these may be used as guesses to
       violate system security.

       You can find advices on how to choose a strong password on
       http://en.wikipedia.org/wiki/Password_strength

OPTIONS
       The options which apply to the passwd command are:

       -a, --all
	   This	option can be used only	with -S	and causes show	status for all
	   users.

       -d, --delete
	   Delete a user's password (make it empty). This is a quick way to
	   disable a password for an account. It will set the named account
	   passwordless.

       -e, --expire
	   Immediately expire an account's password. This in effect can	force
	   a user to change his/her password at	the user's next	login.

       -h, --help
	   Display help	message	and exit.

       -i, --inactive INACTIVE
	   This	option is used to disable an account after the password	has
	   been	expired	for a number of	days. After a user account has had an
	   expired password for	INACTIVE days, the user	may no longer sign on
	   to the account.

       -k, --keep-tokens
	   Indicate password change should be performed	only for expired
	   authentication tokens (passwords). The user wishes to keep their
	   non-expired tokens as before.

       -l, --lock
	   Lock	the password of	the named account. This	option disables	a
	   password by changing	it to a	value which matches no possible
	   encrypted value (it adds a '!' at the beginning of the password).

	   Note	that this does not disable the account.	The user may still be
	   able	to login using another authentication token (e.g. an SSH key).
	   To disable the account, administrators should use usermod
	   --expiredate	1 (this	set the	account's expire date to Jan 2,	1970).

	   Users with a	locked password	are not	allowed	to change their
	   password.

       -n, --mindays MIN_DAYS
	   Set the minimum number of days between password changes to
	   MIN_DAYS. A value of	zero for this field indicates that the user
	   may change his/her password at any time.

       -q, --quiet
	   Quiet mode.

       -r, --repository	REPOSITORY
	   change password in REPOSITORY repository

       -R, --root CHROOT_DIR
	   Apply changes in the	CHROOT_DIR directory and use the configuration
	   files from the CHROOT_DIR directory.

       -S, --status
	   Display account status information. The status information consists
	   of 7	fields.	The first field	is the user's login name. The second
	   field indicates if the user account has a locked password (L), has
	   no password (NP), or	has a usable password (P). The third field
	   gives the date of the last password change. The next	four fields
	   are the minimum age,	maximum	age, warning period, and inactivity
	   period for the password. These ages are expressed in	days.

       -u, --unlock
	   Unlock the password of the named account. This option re-enables a
	   password by changing	the password back to its previous value	(to
	   the value before using the -l option).

       -w, --warndays WARN_DAYS
	   Set the number of days of warning before a password change is
	   required. The WARN_DAYS option is the number	of days	prior to the
	   password expiring that a user will be warned	that his/her password
	   is about to expire.

       -x, --maxdays MAX_DAYS
	   Set the maximum number of days a password remains valid. After
	   MAX_DAYS, the password is required to be changed.

CAVEATS
       Password	complexity checking may	vary from site to site.	The user is
       urged to	select a password as complex as	he or she feels	comfortable
       with.

       Users may not be	able to	change their password on a system if NIS is
       enabled and they	are not	logged into the	NIS server.

       passwd uses PAM to authenticate users and to change their passwords.

FILES
       /etc/passwd
	   User	account	information.

       /etc/shadow
	   Secure user account information.

       /etc/pam.d/passwd
	   PAM configuration for passwd.

EXIT VALUES
       The passwd command exits	with the following values:

       0
	   success

       1
	   permission denied

       2
	   invalid combination of options

       3
	   unexpected failure, nothing done

       4
	   unexpected failure, passwd file missing

       5
	   passwd file busy, try again

       6
	   invalid argument to option

SEE ALSO
       chpasswd(8), passwd(5), shadow(5), usermod(8).

shadow-utils 4.1.5.1		  05/25/2012			     PASSWD(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CAVEATS | FILES | EXIT VALUES | SEE ALSO

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<https://www.freebsd.org/cgi/man.cgi?query=passwd&manpath=Debian+7.7.0>

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