usr.bin/passwd/passwd.1

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.\"	@(#)passwd.1	8.1 (Berkeley) 6/6/93
.\" $FreeBSD: src/usr.bin/passwd/passwd.1,v 1.18.2.5 2002/06/21 15:28:37 charnier Exp $
.\" $DragonFly: src/usr.bin/passwd/passwd.1,v 1.6 2006/11/17 23:23:05 swildner Exp $
.\"
.Dd June 6, 1993
.Dt PASSWD 1
.Os
.Sh NAME
.Nm passwd ,
.Nm yppasswd
.Nd modify a user's password
.Sh SYNOPSIS
.Nm
.Op Fl l
.Op Ar user
.Nm yppasswd
.Op Fl l
.Op Fl y
.Op Fl d Ar domain
.Op Fl h Ar host
.Op Fl o
.Sh DESCRIPTION
The
.Nm
utility changes the user's local, Kerberos, or NIS password.
If the user is not the super-user,
.Nm
first prompts for the current password and will not continue unless the correct
password is entered.
.Pp
When entering the new password, the characters entered do not echo, in order to
avoid the password being seen by a passer-by.
The
.Nm
utility prompts for the new password twice in order to detect typing errors.
.Pp
The new password should be at least six characters long (which
may be overridden using the
.Xr login.conf 5
.Dq minpasswordlen
setting for a user's login class) and not purely alphabetic.
Its total length must be less than
.Dv _PASSWORD_LEN
(currently 128 characters).
.Pp
The new password should contain a mixture of upper and lower case
characters (which may be overridden using the
.Xr login.conf 5
.Dq 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.
.Pp
Once the password has been verified,
.Nm
communicates the new password information to
the Kerberos authenticating host.
.Bl -tag -width flag
.It Fl 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,
.Xr pwd_mkdb 8
is used to update the password databases.
.El
When changing local or NIS password, the next password change date
is set according to
.Dq passwordtime
capability in the user's login class.
.Pp
To change another user's Kerberos password, one must first
run
.Xr kinit 1
followed by
.Xr passwd 1 .
The super-user is not required to provide a user's current password
if only the local password is modified.
.Sh NIS INTERACTION
The
.Nm
utility has built-in support for NIS.
If a user exists in the NIS password
database but does not exist locally,
.Nm
automatically switches into
.Dq yppasswd
mode.
If the specified
user does not exist in either the local password database of the
NIS password maps,
.Nm
returns an error.
.Pp
When changing an NIS password, unprivileged users are required to provide
their old password for authentication (the
.Xr 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.
.Pp
The following additional options are supported for use with NIS:
.Bl -tag -width flag
.It Fl y
The
.Fl y
flag overrides
.Nm Ns 's
checking heuristics and forces
it into NIS mode.
.It Fl l
When NIS is enabled, the
.Fl l
flag can be used to force
.Nm
into
.Dq 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
.Dq placeholder
users such as
.Pa bin
or
.Pa daemon
in both the NIS password maps and the local user database.
By
default,
.Nm
will try to change the NIS password.
The
.Fl l
flag can be used to change the local password instead.
.It Fl d Ar domain
Specify what domain to use when changing an NIS password.
By default,
.Nm
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
.Nm
command needs to be told what domain to operate on.
.It Fl h Ar host
Specify the name of an NIS server.
This option, in conjunction
with the
.Fl d
option, can be used to change an NIS password on a non-local NIS
server.
When a domain is specified with the
.Fl d
option and
.Nm
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
.Dq localhost .
This can be overridden with the
.Fl 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.
.Pp
.It Fl 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.
.El
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/master.passwd
The user database
.It Pa /etc/passwd
A Version 7 format password file
.It Pa /etc/passwd.XXXXXX
Temporary copy of the password file
.It Pa /etc/login.conf
Login class capabilities database
.It Pa /etc/auth.conf
configure authentication services
.El
.Sh SEE ALSO
.Xr chpass 1 ,
.Xr kinit 1 ,
.Xr login 1 ,
.Xr login.conf 5 ,
.Xr passwd 5 ,
.Xr kerberos 8 ,
.Xr kpasswdd 8 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Rs
.%A Robert Morris
.%A Ken Thompson
.%T "UNIX password security"
.Re
.Sh NOTES
The
.Xr yppasswd 1
command is really only a link to
.Nm .
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .