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.\"	@(#)passwd.1	8.1 (Berkeley) 6/6/93
.\"
.Dd June 6, 1993
.Dt PASSWD 1
.Os BSD 4
.Sh NAME
.Nm passwd, yppasswd
.Nd modify a user's password
.Sh SYNOPSIS
.Nm passwd
.Op Fl l
.Op Ar user
.Sh DESCRIPTION
.Nm Passwd
changes the user's Kerberos 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.
.Pp
The new password should be at least six characters long and not
purely alphabetic.
Its total length must be less than
.Dv _PASSWORD_LEN
(currently 128 characters).
Numbers, upper case letters and meta characters
are encouraged.
.Pp
Once the password has been verified,
.Nm passwd
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
.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
.Nm Passwd
has built-in support for NIS. If a user exists in the NIS password
database but does not exist locally,
.Nm passwd
automatically switches into ``yppasswd'' mode. If the specified
user does not exist in either the local password database of the
NIS password maps,
.Nm passwd
returns an error.
The following additional options are supported for use with NIS:
.Bl -tag -width flag
.It Fl y
The
.Fl y
flag overrides
.Nm passwd '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 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
.Pa bin
or
.Pa daemon
in both the NIS password maps and the local user database. By
default,
.Nm passwd
will try to change the NIS password. The
.Fl l
flag can be used to change the local password instead.
.El
.Pp
When changing an NIS password, the user is required to provide
the old password for authentication (the
.Xr 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: the only way for an administrator to override a
user's NIS password is by modifying the NIS password maps on
the master NIS server.
.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
.El
.Sh SEE ALSO
.Xr chpass 1 ,
.Xr kerberos 1 ,
.Xr kinit 1 ,
.Xr login 1 ,
.Xr passwd 5 ,
.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 passwd .
.Sh HISTORY
A
.Nm passwd
command appeared in
.At v6 .