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.\"	from: @(#)passwd.1	6.11 (Berkeley) 7/24/91
.\"
.Dd $Mdocdate: July 27 2015 $
.Dt PASSWD 1
.Os
.Sh NAME
.Nm passwd
.Nd modify a user's password
.Sh SYNOPSIS
.Nm passwd
.Op Fl l | y
.Op Ar user
.Sh DESCRIPTION
.Nm
changes the user's local or YP password.
If no
.Ar user
is specified, the user's login name is used (see
.Xr logname 1 ) .
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.
.El
.Pp
If no flags are specified and 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
Password encryption parameters depend on the configuration of the
.Dq localcipher
capability in
.Xr login.conf 5 .
If none is specified, then blowfish with 8 rounds is used.
.Sh FILES
.Bl -tag -width /etc/master.passwd -compact
.It Pa /etc/login.conf
configuration options
.It Pa /etc/master.passwd
user database
.It Pa /etc/passwd
user database, with confidential information removed
.It Pa /etc/passwd.XXXXXX
temporary copy of the password file
.It Pa /etc/ptmp
lock file for the passwd database
.El
.Sh DIAGNOSTICS
.Bl -diag
.It "Attempting to 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 change 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 encrypt 1 ,
.Xr logname 1 ,
.Xr login.conf 5 ,
.Xr passwd 5 ,
.Xr pwd_mkdb 8 ,
.Xr vipw 8
.Rs
.%A Robert Morris
.%A Ken Thompson
.%T Password security: a case history
.%J Communications of the ACM
.%V Volume 22
.%N Issue 11
.%D Nov. 1979
.%P 594\(en597
.Re
.Sh HISTORY
A
.Nm
command appeared in
.At v3 .