passwd man page on Peanut

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PASSWD(1)			 User Commands			     PASSWD(1)

NAME
       passwd - change user password

SYNOPSIS
       passwd [options] login

DESCRIPTION
       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 user's 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 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.

   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 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

       ·  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.

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
	      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 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 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
       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.

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).

User Commands			  02/28/2006			     PASSWD(1)
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