Provided by: passwd_4.0.13-7ubuntu3_i386 bug

NAME

       passwd - change user password

SYNOPSIS

       passwd [-f -s] [name]

       passwd [-g] [-r -R] group

       passwd [-x max] [-n min] [-w warn] [-i inact] login

       passwd [-l -u -d -S -e] login

DESCRIPTION

       passwd changes passwords for user and group accounts. A normal user may
       only change the password for his/her own account, the super user may
       change the password for any account. The administrator of a group may
       change the password for the group.  passwd also changes account
       information, such as the full name of the user, user’s login shell, or
       password expiry date and interval.

       The -s option makes passwd call chsh to change the user’s shell. The -f
       option makes passwd call chfn to change the user’s gecos information.
       These two options are only meant for compatibility, since the other
       programs can be called directly.

   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 super user 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 for a replacement password. This password is
       tested for complexity. As a general guideline, passwords should consist
       of 6 to 8 characters including one or more from each of 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.

       If the password is accepted, passwd will prompt again and compare the
       second entry against the first. Both entries are required to match in
       order for the password to be changed.

   Group passwords
       When the -g option is used, the password for the named group is
       changed. The user must either be the super user, or a group
       administrator for the named group. The current group password is not
       prompted for. The -r option is used with the -g option to remove the
       current password from the named group. This allows group access to all
       members. The -R option is used with the -g option to restrict the named
       group for all users.

   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 UNIX System encryption
       method is based on the NBS DES algorithm and is very secure. 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.

       Your password must easily remembered so that you will not be forced to
       write it on a piece of paper. This can be accomplished by appending two
       small words together and separating each with a special character or
       digit. For example, Pass%word.

       Other methods of construction involve selecting an easily remembered
       phrase from literature and selecting the first or last letter from each
       word. An example of this is:

       ·  Ask not for whom the bell tolls

       ·  which produces

       ·  An4wtbt

       You may be reasonably sure few crackers will have included this in
       their dictionaries. You should, however, select your own methods for
       constructing passwords and not rely exclusively on the methods given
       here.

   Notes about group passwords
       Group passwords are an inherent security problem since more than one
       person is permitted to know the password. However, groups are a useful
       tool for permitting co-operation between different users.

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

       -l, --lock
              Lock the named account. This option disables an account by
              changing the password to a value which matches no possible
              encrypted value.

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

       -q, --quiet
              quiet mode

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

       -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 is locked (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 named account. This option re-enables an account by
              changing the password back to its previous value (to value
              before using -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 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

       Not all options may be supported. Password complexity checking may vary
       from site to site. The user is urged to select a password as complex as
       he 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.

FILES

       /etc/passwd
              user account information

       /etc/shadow
              secure user account information

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

       group(5), passwd(5), shadow(5).

AUTHOR

       Julianne Frances Haugh <jockgrrl@ix.netcom.com>