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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] [-h	host] [-o]

DESCRIPTION
     The passwd	utility	changes	the user's local, Kerberos, or NIS password.
     If	the user is not	the super-user,	passwd first prompts for the current
     password and will not continue unless the correct password	is entered.

     When entering the new password, the characters entered do not echo, in
     order to avoid the	password being seen by a passer-by.  The passwd	util-
     ity prompts for the new password twice in order to	detect typing errors.

     The new password should be	at least six characters	long (which may	be
     overridden	using the login.conf(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).

     The new password should contain a mixture of upper	and lower case charac-
     ters (which may be	overridden using the login.conf(5) "mixpasswordcase"
     setting for a user's login	class).	 Allowing lower	case passwords may be
     useful where the password file will be used in situations where only
     lower case	passwords are permissible, such	as when	using Samba to authen-
     ticate Windows clients.  In all other situations, numbers,	upper case
     letters 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 "passwordtime" 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
     The passwd	utility	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	local password database	of the NIS password maps, passwd re-
     turns 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 with 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
	   operate on.

     -h	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 overridden
	   with	the -h 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
	   determined by querying any NIS server (master or slave) in a	do-
	   main, 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
     /etc/auth.conf	 configure authentication services

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.

BSD				 June 6, 1993				   BSD

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

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