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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 total length of the password must be less than	_PASSWORD_LEN (cur-
     rently 128	characters).

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

     The following option is available:

     -l	     Cause 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.  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 ei-
     ther the local password database or 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	     Override 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 pass-
	     word 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 instead.

     -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 op-
	     tion and passwd is	unable to determine the	name of	the NIS	master
	     server (possibly because the local	domainname is not 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 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
	     instead.  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),	kinit(1), login(1), login.conf(5), passwd(5), kerberos(8),
     kpasswdd(8), pam_passwdqc(8), pw(8), pwd_mkdb(8), vipw(8)

     Robert Morris and Ken Thompson, UNIX password security.

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

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

BSD			       February	14, 2014			   BSD

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

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