NAME
passwd - change password file information

SYNOPSIS
passwd [ -f ] [ -s ] [ name ]

DESCRIPTION
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 six characters long, must not
contain part of the login or user names, and must not be in a list
of too commonly used passwords.

The password used by system applications (e.g. login(1), su(1),
etc.) to authenticate your user identity is stored encrypted in a
world read-protected location for extra security.

Only the owner of the name or the super-user may change a password;
the owner must prove he knows the old password (or the system
password when changing a public 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 listed in /usr/etc/shells unless you
are the super-user. If /usr/etc/shells does not exist, the only
shells that may be specified are /bin/sh and /bin/csh.

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.
It is a good idea to run finger(1) 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.

FILES
/etc/passwd The file containing all of this information
/etc/cryptkeys The file containing the system passwords
/etc/cryptvers The encryption algorithm version number
/usr/etc/shells The list of approved shells

SEE ALSO
login(1), su(1), finger(1), passwd(5), crypt(3), okpasswd(3)*
Robert Morris and Ken Thompson, UNIX password security

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* Not currently supported under MachTen