.\" Copyright (C) 2000, 2001, 2004, 2005, 2007-2009, 2014-2020 Internet Systems Consortium, Inc. ("ISC")
.\" 
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.\"     Title: lwresd
.\"    Author: 
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 2009-01-20
.\"    Manual: BIND9
.\"    Source: ISC
.\"  Language: English
.\"
.TH "LWRESD" "8" "2009\-01\-20" "ISC" "BIND9"
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.SH "NAME"
lwresd \- lightweight resolver daemon
.SH "SYNOPSIS"
.HP \w'\fBlwresd\fR\ 'u
\fBlwresd\fR [\fB\-c\ \fR\fB\fIconfig\-file\fR\fR] [\fB\-C\ \fR\fB\fIconfig\-file\fR\fR] [\fB\-d\ \fR\fB\fIdebug\-level\fR\fR] [\fB\-f\fR] [\fB\-g\fR] [\fB\-i\ \fR\fB\fIpid\-file\fR\fR] [\fB\-m\ \fR\fB\fIflag\fR\fR] [\fB\-n\ \fR\fB\fI#cpus\fR\fR] [\fB\-P\ \fR\fB\fIport\fR\fR] [\fB\-p\ \fR\fB\fIport\fR\fR] [\fB\-s\fR] [\fB\-t\ \fR\fB\fIdirectory\fR\fR] [\fB\-u\ \fR\fB\fIuser\fR\fR] [\fB\-v\fR] [[\fB\-4\fR] | [\fB\-6\fR]]
.SH "DESCRIPTION"
.PP
\fBlwresd\fR
is the daemon providing name lookup services to clients that use the BIND 9 lightweight resolver library\&. It is essentially a stripped\-down, caching\-only name server that answers queries using the BIND 9 lightweight resolver protocol rather than the DNS protocol\&.
.PP
\fBlwresd\fR
listens for resolver queries on a UDP port on the IPv4 loopback interface, 127\&.0\&.0\&.1\&. This means that
\fBlwresd\fR
can only be used by processes running on the local machine\&. By default, UDP port number 921 is used for lightweight resolver requests and responses\&.
.PP
Incoming lightweight resolver requests are decoded by the server which then resolves them using the DNS protocol\&. When the DNS lookup completes,
\fBlwresd\fR
encodes the answers in the lightweight resolver format and returns them to the client that made the request\&.
.PP
If
/etc/resolv\&.conf
contains any
\fBnameserver\fR
entries,
\fBlwresd\fR
sends recursive DNS queries to those servers\&. This is similar to the use of forwarders in a caching name server\&. If no
\fBnameserver\fR
entries are present, or if forwarding fails,
\fBlwresd\fR
resolves the queries autonomously starting at the root name servers, using a built\-in list of root server hints\&.
.SH "OPTIONS"
.PP
\-4
.RS 4
Use IPv4 only even if the host machine is capable of IPv6\&.
\fB\-4\fR
and
\fB\-6\fR
are mutually exclusive\&.
.RE
.PP
\-6
.RS 4
Use IPv6 only even if the host machine is capable of IPv4\&.
\fB\-4\fR
and
\fB\-6\fR
are mutually exclusive\&.
.RE
.PP
\-c \fIconfig\-file\fR
.RS 4
Use
\fIconfig\-file\fR
as the configuration file instead of the default,
/etc/lwresd\&.conf\&.
\fB\-c\fR
can not be used with
\fB\-C\fR\&.
.RE
.PP
\-C \fIconfig\-file\fR
.RS 4
Use
\fIconfig\-file\fR
as the configuration file instead of the default,
/etc/resolv\&.conf\&.
\fB\-C\fR
can not be used with
\fB\-c\fR\&.
.RE
.PP
\-d \fIdebug\-level\fR
.RS 4
Set the daemon\*(Aqs debug level to
\fIdebug\-level\fR\&. Debugging traces from
\fBlwresd\fR
become more verbose as the debug level increases\&.
.RE
.PP
\-f
.RS 4
Run the server in the foreground (i\&.e\&. do not daemonize)\&.
.RE
.PP
\-g
.RS 4
Run the server in the foreground and force all logging to
stderr\&.
.RE
.PP
\-i \fIpid\-file\fR
.RS 4
Use
\fIpid\-file\fR
as the PID file instead of the default,
/var/run/lwresd/lwresd\&.pid\&.
.RE
.PP
\-m \fIflag\fR
.RS 4
Turn on memory usage debugging flags\&. Possible flags are
\fIusage\fR,
\fItrace\fR,
\fIrecord\fR,
\fIsize\fR, and
\fImctx\fR\&. These correspond to the ISC_MEM_DEBUGXXXX flags described in
<isc/mem\&.h>\&.
.RE
.PP
\-n \fI#cpus\fR
.RS 4
Create
\fI#cpus\fR
worker threads to take advantage of multiple CPUs\&. If not specified,
\fBlwresd\fR
will try to determine the number of CPUs present and create one thread per CPU\&. If it is unable to determine the number of CPUs, a single worker thread will be created\&.
.RE
.PP
\-P \fIport\fR
.RS 4
Listen for lightweight resolver queries on port
\fIport\fR\&. If not specified, the default is port 921\&.
.RE
.PP
\-p \fIport\fR
.RS 4
Send DNS lookups to port
\fIport\fR\&. If not specified, the default is port 53\&. This provides a way of testing the lightweight resolver daemon with a name server that listens for queries on a non\-standard port number\&.
.RE
.PP
\-s
.RS 4
Write memory usage statistics to
stdout
on exit\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBNote\fR
.ps -1
.br
This option is mainly of interest to BIND 9 developers and may be removed or changed in a future release\&.
.sp .5v
.RE
.RE
.PP
\-t \fIdirectory\fR
.RS 4
Chroot to
\fIdirectory\fR
after processing the command line arguments, but before reading the configuration file\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBWarning\fR
.ps -1
.br
This option should be used in conjunction with the
\fB\-u\fR
option, as chrooting a process running as root doesn\*(Aqt enhance security on most systems; the way
\fBchroot(2)\fR
is defined allows a process with root privileges to escape a chroot jail\&.
.sp .5v
.RE
.RE
.PP
\-u \fIuser\fR
.RS 4
Setuid to
\fIuser\fR
after completing privileged operations, such as creating sockets that listen on privileged ports\&.
.RE
.PP
\-v
.RS 4
Report the version number and exit\&.
.RE
.SH "FILES"
.PP
/etc/resolv\&.conf
.RS 4
The default configuration file\&.
.RE
.PP
/var/run/lwresd\&.pid
.RS 4
The default process\-id file\&.
.RE
.SH "SEE ALSO"
.PP
\fBnamed\fR(8),
\fBlwres\fR(3),
\fBresolver\fR(5)\&.
.SH "AUTHOR"
.PP
\fBInternet Systems Consortium, Inc\&.\fR
.SH "COPYRIGHT"
.br
Copyright \(co 2000, 2001, 2004, 2005, 2007-2009, 2014-2020 Internet Systems Consortium, Inc. ("ISC")
.br