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.\"	from: @(#)passwd.1	6.11 (Berkeley) 7/24/91
.\"
.Dd July 24, 1991
.Dt PASSWD 1
.Os
.Sh NAME
.Nm passwd
.Nd modify a user's password
.Sh SYNOPSIS
.Nm passwd
.Bk -words
.Op Fl l
.Op Fl y
.Op Fl K
.Op Ar user
.Ek
.Sh DESCRIPTION
.Nm
changes the user's local, Kerberos, or YP 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).
A mixture of both lower and uppercase letters, numbers, and
meta-characters is encouraged.
.Pp
The quality of the password can be enforced by specifying an external
checking program via the
.Dq passwordcheck
variable in
.Xr login.conf 5 .
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl l
Causes the password to be updated only in the local password file.
When changing only the local password,
.Xr pwd_mkdb 8
is used to update the password databases.
.It Fl y
Forces the YP password database entry to be changed, even if
the user has an entry in the local database.
The
.Xr rpc.yppasswdd 8
daemon should be running on the YP master server.
.It Fl K
Forces the change to affect the Kerberos 5 database, even
if the user has a password in the local database.
Once the password has been verified,
.Nm
communicates the new password information to the Kerberos authenticating host.
.El
.Pp
This is the behavior if no flags are specified:
if Kerberos is active then
.Nm
will talk to the Kerberos server (even if the user has an entry
in the local database).
If the password is not in the local password database, then
an attempt is made to use the YP database.
.Pp
The superuser is not required to provide a user's current password
if only the local password is modified.
.Pp
Which type of cipher is used to encrypt the password information
depends on the configuration in
.Xr login.conf 5 .
It can be different for local
.Po Do localcipher Dc Pc
and YP
.Po Do ypcipher Dc Pc
passwords.
If none is specified, then blowfish with 6 rounds is used for local
.Po Do localcipher Dc Pc
and old is used for YP
.Po Do ypcipher Dc Pc
by default.
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It /etc/login.conf
configuration options
.It Pa /etc/master.passwd
user database
.It Pa /etc/passwd
a 6th Edition-style password file
.It Pa /etc/passwd.XXXXXX
temporary copy of the password file
.It /etc/ptmp
lock file for the passwd database
.El
.Sh DIAGNOSTICS
.Bl -diag
.It "Attempting lock password file, please wait or press ^C to abort"
.Pp
The password file is currently locked by another process;
.Nm
will keep trying to lock the password file until it succeeds or
you hit the interrupt character (control-C by default).
If
.Nm
is interrupted while trying to gain the lock the password changed will
be lost.
.Pp
If the process holding the lock was prematurely terminated the lock
file may be stale and
.Nm
will wait forever trying to lock the password file.
To determine whether a live process is actually holding the lock, the
admin may run the following:
.Bd -literal -offset indent
$ fstat /etc/ptmp
.Ed
.Pp
If no process is listed, it is safe to remove the
.Pa /etc/ptmp
file to clear the error.
.El
.Sh SEE ALSO
.Xr chpass 1 ,
.Xr kinit 1 ,
.Xr login 1 ,
.Xr login.conf 5 ,
.Xr passwd 5 ,
.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 v3 .