passwd(1) — Linux manual page

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 their 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 their 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 advice 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 their 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 their 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 their
           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.

           Passing the number -1 as MAX_DAYS will remove checking a
           password's validity.

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 
       ⟨https://github.com/shadow-maint/shadow⟩.  If you have a bug
       report for this manual page, send it to
       pkg-shadow-devel@alioth-lists.debian.net.  This page was obtained
       from the project's upstream Git repository
       ⟨https://github.com/shadow-maint/shadow⟩ on 2020-12-18.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2020-11-08.)  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 4.8.1             12/18/2020                      PASSWD(1)

Pages that refer to this page: ldappasswd(1)login(1)login(1@@shadow-utils)crypt(3)pts(4)login.defs(5)passwd(5)passwd(5@@shadow-utils)shadow(5)chpasswd(8)groupadd(8)groupdel(8)groupmems(8)groupmod(8)newusers(8)useradd(8)userdel(8)usermod(8)vipw(8@@util-linux)