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PASSWD(1)			 User Commands			     PASSWD(1)

       passwd - change user password

       passwd [options] [LOGIN]

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

   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 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

   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

       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 be 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


       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

       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

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

       -e, --expire
	  Immediately expire an accounts password. This in effect can force a
	  user to change his/her password at the users 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 named account. This option disables an account by changing
	  the password to a value which matches no possible encrypted value.

       -m, --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

       -S, --status
	  Display account status information. The status information consists
	  of 7 fields. The first field is the users 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 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.

       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 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.

	  User account information.

	  Secure user account information.

       The passwd command exits with the following values:


	  permission denied

	  invalid combination of options

	  unexpected failure, nothing done

	  unexpected failure, passwd file missing

	  passwd file busy, try again

	  invalid argument to option

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

User Commands			  02/27/2007			     PASSWD(1)

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