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PASSWD(1)		  BSD General Commands Manual		     PASSWD(1)

NAME
     passwd, yppasswd -- modify	a user's password

SYNOPSIS
     passwd [-l] [user]
     yppasswd [-l] [-y]	[-d domain] [-s	host] [-o]

DESCRIPTION
     Passwd changes the	user's local, Kerberos,	or NIS password.  First, the
     user is prompted for their	current	password.  If the current password is
     correctly typed, a	new password is	requested.  The	new password must be
     entered twice to avoid typing errors.

     The new password should be	at least six characters	long (which may	be
     overridden	using the login.cap(5) "minpasswordlen"	setting	for a user's
     login class) and not purely alphabetic.  Its total	length must be less
     than _PASSWORD_LEN	(currently 128 characters).  Numbers, upper case let-
     ters and meta characters are encouraged.

     Once the password has been	verified, passwd communicates the new password
     information to the	Kerberos authenticating	host.

     -l	   This	option causes the password to be updated only in the local
	   password file, and not with the Kerberos database.  When changing
	   only	the local password, pwd_mkdb(8)	is used	to update the password
	   databases.

     When changing local or NIS	password, the next password change date	is set
     according to "passwordperiod" capability in the user's login class.

     To	change another user's Kerberos password, one must first	run kinit(1)
     followed by passwd(1).  The super-user is not required to provide a
     user's current password if	only the local password	is modified.

NIS INTERACTION
     Passwd has	built-in support for NIS. If a user exists in the NIS password
     database but does not exist locally, passwd automatically switches	into
     ``yppasswd'' mode.	If the specified user does not exist in	either the lo-
     cal password database of the NIS password maps, passwd returns an error.

     When changing an NIS password, unprivileged users are required to provide
     their old password	for authentication (the	rpc.yppasswdd(8) daemon	re-
     quires the	original password before it will allow any changes to the NIS
     password maps).  This restriction applies even to the super-user, with
     one important exception: the password authentication is bypassed for the
     super-user	on the NIS master server. This means that the super-user on
     the NIS master server can make unrestricted changes to anyone's NIS pass-
     word. The super-user on NIS client	systems	and NIS	slave servers still
     needs to provide a	password before	the update will	be processed.

     The following additional options are supported for	use with NIS:

     -y	   The -y flag overrides passwd	's checking heuristics and forces it
	   into	NIS mode.

     -l	   When	NIS is enabled,	the -l flag can	be used	to force passwd	into
	   ``local only'' mode.	This flag can be used to change	the entry for
	   a local user	when an	NIS user exists	when the same login name.  For
	   example, you	will sometimes find entries for	system ``placeholder''
	   users such as bin or	daemon in both the NIS password	maps and the
	   local user database.	By default, passwd will	try to change the NIS
	   password. The -l flag can be	used to	change the local password in-
	   stead.

     -d	domain
	   Specify what	domain to use when changing an NIS password. By	de-
	   fault, passwd assumes that the system default domain	should be
	   used. This flag is primarily	for use	by the superuser on the	NIS
	   master server: a single NIS server can support multiple domains. It
	   is also possible that the domainname	on the NIS master may not be
	   set (it is not necessary for	an NIS server to also be a client) in
	   which case the passwd command needs to be told what domain to oper-
	   ate on.

     -s	host
	   Specify the name of an NIS server. This option, in conjunction with
	   the -d option, can be used to change	an NIS password	on a non-local
	   NIS server. When a domain is	specified with the -d option and
	   passwd is unable to determine the name of the NIS master server
	   (possibly because the local domainname isn't	set), the name of the
	   NIS master is assumed to be ``localhost''. This can be overriden
	   with	the -s flag. The specified hostname need not be	the name of an
	   NIS master: the name	of the NIS master for a	given map can be de-
	   termined by querying	any NIS	server (master or slave) in a domain,
	   so specifying the name of a slave server will work equally well.

     -o	   Do not automatically	override the password authentication checks
	   for the super-user on the NIS master	server;	assume 'old' mode in-
	   stead. This flag is of limited practical use	but is useful for
	   testing.

FILES
     /etc/master.passwd	 The user database
     /etc/passwd	 A Version 7 format password file
     /etc/passwd.XXXXXX	 Temporary copy	of the password	file
     /etc/login.conf	 Login class capabilities database

SEE ALSO
     chpass(1),	kerberos(1), kinit(1), login(1), login.conf(5),	passwd(5),
     kpasswdd(8), pwd_mkdb(8), vipw(8)

     Robert Morris and Ken Thompson, UNIX password security.

NOTES
     The yppasswd(1) command is	really only a link to passwd.

HISTORY
     A passwd command appeared in Version 6 AT&T UNIX.

4th Berkeley Distribution	 June 6, 1993	     4th Berkeley Distribution

NAME | SYNOPSIS | DESCRIPTION | NIS INTERACTION | FILES | SEE ALSO | NOTES | HISTORY

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