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.\"	from: @(#)passwd.1    8.1 (Berkeley) 6/6/93
.\"
.Dd February 25, 2005
.Dt PASSWD 1
.Os
.Sh NAME
.Nm passwd
.Nd modify a user's password
.Sh SYNOPSIS
.Nm
.Op Ar user
.Nm
.Oo Fl d Ar files | Fl l Oc
.Op Ar user
.Nm
.Oo Fl d Ar nis | Fl y Oc
.Op Ar user
.Nm
.Oo Fl d Ar krb5 | Fl k Oc
.Op Ar principal
.Sh DESCRIPTION
.Nm
changes the user's 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
All options may not be available on all systems.
.Bl -tag -width flag
.It Fl d Ar database
This option specifies the password database that should be updated.  The
following databases are supported:
.Bl -tag -width files
.It files
This specifies that the password change should be applied to the local
password file.
When changing only the local password,
.Nm
uses
.Xr pwd_mkdb 8
to update the password databases.
.It nis
This specifies that the password change should be applied to the NIS
password database.
The
.Xr rpc.yppasswdd 8
daemon should be running on the master NIS server.
.It krb5
This specifies that the user's Kerberos 5 password should be changed.
The host must be configured to use Kerberos.
See
.Xr krb5.conf 5 .
.El
.It Fl l
This is the equivalent of
.Fl d Ar files .
.It Fl y
This is the equivalent of
.Fl d Ar nis .
.It Fl k
This is the equivalent of
.Fl d Ar krb5 .
.El
.Pp
If a password database is not specified,
.Nm
will change the password database as determined by the
Pluggable Authentication Module
.Pq PAM
library.
.Pp
The type of cipher used to encrypt the password depends on the configuration
in
.Xr passwd.conf 5 .
It can be different for local and NIS passwords.
.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 login 1 ,
.Xr pwhash 1 ,
.Xr passwd 5 ,
.Xr passwd.conf 5 ,
.Xr pam 8 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Rs
.%A Robert Morris
.%A Ken Thompson
.%T "UNIX password security"
.Re
.Sh HISTORY
A
.Nm
command appeared in
.At v6 .