passwd, chfn, chsh - change local or NIS  password  informa-

     passwd [ -l | -y ] [ -afs ] [ -d [ username ] ] [  -e  user-
     name ]
     [ -F filename ] [ -n numdays username ]
     [ -x numdays username ] [ username ]

     chfn [ -l | -y ] [ -f ] [ -F filename ] [ username ]

     chsh [ -l | -y ] [ -s ] [ -F filename ] [ username ]

     passwd changes (or installs) a  password,  login  shell  (-s
     option),  or  full name (-f option) associated with the user
     username (your own  by  default).   chsh  is  equivalent  to
     passwd  with the -s option, and chfn is equivalent to passwd
     with the -f option.

     Use `passwd -y' or yppasswd(1) to change  your  password  in
     the Network Information Service (NIS).  This will not affect
     your local password, or your password on any remote machines
     on which you have accounts.  passwd calls yppasswd automati-
     cally if you do not have an entry in the local passwd  file,
     and the -l option is not specified.

     When changing a password, passwd prompts for the  old  pass-
     word  and  then  for the new one.  You must supply both, and
     the new password must be typed twice to forestall mistakes.

     If password aging is enabled, the  first  time  an  ordinary
     user enters the new password passwd checks to see if the old
     password has "aged" sufficiently.  Password "aging"  is  the
     amount  of time (usually a certain number of days) that must
     elapse between password changes.  If "aging" is insufficient
     the new password is rejected and passwd terminates.

     New passwords should be at least five  characters  long,  if
     they  combine upper-case and lower-case letters, or at least
     six characters long if in monocase.  Users that  persist  in
     entering  shorter passwords are compromising their own secu-
     rity. The number of significant characters in a password  is
     eight, although longer passwords will be accepted.

     Only the owner of the name or the super-user  may  change  a
     password;  the  owner  must prove he knows the old password.
     The super-user can change any password and is not forced  to
     comply with password aging requirements.

     When changing 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
     /etc/shells  unless  you are the super-user.  If /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 changing a full name, passwd displays the current  full
     name,  enclosed between brackets, and prompts for a new full
     name.  If you type a RETURN, the full name is  not  changed.
     If the full name is to be made blank, you must type the word

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

     -a   Display the name and aging information for  all  users.
          Can only be invoked by the super-user.

     -f   Change the full name.

     -l   Change the local password, login shell, or  full  name.
          If  username  exists  in the local passwd file, this is
          the default.

     -s   Change the login shell.

     -y   Change passwd, login shell, or full  name  in  the  NIS

     -d [username]
          Display the name and aging information for  the  caller
          or  the  user  specified  if  the invoker has the right

     -e username
          Expire the password for the user name  specified.   Can
          only be invoked by the super-user.

     -F filename
          Treat filename as the password file.

     -n numdays username
          Set the maturity time of  the  password  for  username.
          Passwords   that  have  not  "aged"  enough  cannot  be
          changed.  Can only be set by the super-user.

     -x numdays username
          Set the expiration time of the password  for  username.
          Can only be set by the super-user.

     /etc/passwd         file containing all of this information
     /etc/shells         list of approved shells

     finger(1), login(1), yppasswd(1), crypt(3), passwd(5)

     Password algorithms do not work with 8-bit characters.  This
     maintains consistency with login file naming rules, which do
     not allow 8-bit characters in login names.  See login(1) for
     explanations about why login is not 8-bit clean.

     The Network Information Service (NIS) was formerly known  as
     Sun  Yellow Pages (YP). The functionality of the two remains
     the same; only the name has changed.