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

PASSWD(1)                       User Commands                      PASSWD(1)

NAME         top

       passwd - change user password

SYNOPSIS         top

       passwd [options] [LOGIN]

DESCRIPTION         top

       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:

       ·   lower case alphabetics

       ·   digits 0 thru 9

       ·   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         top

       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         top

       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         top

       /etc/passwd
           User account information.

       /etc/shadow
           Secure user account information.

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

EXIT VALUES         top

       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         top

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

COLOPHON         top

       This page is part of the shadow-utils (utilities for managing
       accounts and shadow password files) project.  Information about the
       project can be found at ⟨http://pkg-shadow.alioth.debian.org/⟩.  If
       you have a bug report for this manual page, see 
       ⟨http://pkg-shadow.alioth.debian.org/getinvolved.php⟩.  This page was
       obtained from the project's upstream Git repository 
       ⟨git://anonscm.debian.org/git/pkg-shadow/shadow.git⟩ on 2016-10-04.
       If you discover any rendering problems in this HTML version of the
       page, or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the information
       in this COLOPHON (which is not part of the original manual page),
       send a mail to man-pages@man7.org

shadow-utils 4.3                 10/04/2016                        PASSWD(1)