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NAME    [Toc]    [Back]

     passwd, yppasswd -- modify a user's password

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

     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 utility
 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 characters
 (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 authenticate
 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.

     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    [Toc]    [Back]

     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
     returns an error.

     When changing an NIS password, unprivileged users are required to provide
     their old password for authentication (the rpc.yppasswdd(8) daemon
     requires 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
     password.	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

     -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 instead.

     -d domain
	     Specify what domain to use when changing an NIS password.	By
	     default, 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 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

FILES    [Toc]    [Back]

     /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    [Toc]    [Back]

     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    [Toc]    [Back]

     The yppasswd command is really only a link to passwd.

HISTORY    [Toc]    [Back]

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

FreeBSD 5.2.1			 June 6, 1993			 FreeBSD 5.2.1
[ Back ]
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