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@(#)passwd.1 6.1 (Berkeley) 04/29/85

C 4 chfn, chsh, passwd - change password file information passwd [ -f ] [ -s ] [ name ] This command changes (or installs) a password, login shell ( -s option), or GECOS information field ( -f option) associated with the user name (your own name by default).

When altering a password, the program prompts for the current password and then for the new one. The caller must supply both. The new password must be typed twice, to forestall mistakes.

New passwords must be at least four characters long if they use a sufficiently rich alphabet and at least six characters long if monocase. These rules are relaxed if you are insistent enough.

Only the owner of the name or the super-user may change a password; the owner must prove he knows the old password.

When altering a login shell, passwd displays the current login shell and then prompts for the new one. The new login shell must be one of the approved shells: /bin/sh , /bin/csh , /bin/oldcsh , or /usr/new/csh unless you are the super-user.

The super-user may change anyone's login shell; normal users may only change their own login shell.

When altering the GECOS information field, passwd displays the current information, broken into fields, as interpreted by the finger (1) program, among others, and prompts for new values. These fields include a user's ``real life'' name, office room number, office phone number, and home phone number. Included in each prompt is a default value, which is enclosed between brackets. The default value is accepted simply by typing a carriage return. To enter a blank field, the word ``none'' may be typed. Below is a sample run:

"Name [Biff Studsworth II]:"

"Room number (Exs: 597E or 197C) []:" 521E

"Office Phone (Ex: 1632) []:" 1863

"Home Phone (Ex: 987532) [5771546]:" none

Passwd allows phone numbers to be entered with or without hyphens. Because finger only knows about UCB extensions, passwd will insist upon a four digit number (after the hyphens are removed) for office phone numbers. Also, room numbers must be in Evans or Cory; again, this is also because of finger .

It is a good idea to run finger after changing the GECOS information to make sure everything is setup properly.

The super-user may change anyone's GECOS information; normal users may only change their own.

/etc/passwd login(1), finger(1), passwd(5), crypt(3)

Robert Morris and Ken Thompson, UNIX password security

The encoding of the office and extension information is installation dependent.