NAME
lwresd - lightweight resolver daemon
SYNOPSIS
lwresd
[ -c config-file]
[-C config-file] [
-d debug-level] [ -f] [-g]
[-i pid-file] [-m flag]
[-n #cpus] [-P port]
[-p port] [-s]
[-t directory] [ -u user]
[ -v] [-4] [-6]
DESCRIPTION
lwresd 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.
lwresd listens for resolver queries on a UDP port on the IPv4 loopback
interface, 127.0.0.1. This means that
lwresd 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.
Incoming lightweight resolver requests are decoded by the server which then
resolves them using the DNS protocol. When the DNS lookup completes,
lwresd encodes the answers in the lightweight resolver format and
returns them to the client that made the request.
If /etc/resolv.conf contains any
nameserver entries,
lwresd sends
recursive DNS queries to those servers. This is similar to the use of
forwarders in a caching name server. If no
nameserver entries are
present, or if forwarding fails,
lwresd resolves the queries
autonomously starting at the root name servers, using a built-in list of root
server hints.
OPTIONS
-4
Use IPv4 only even if the host machine is
capable of IPv6. -4 and -6 are mutually exclusive.
-6
Use IPv6 only even if the host machine is
capable of IPv4. -4 and -6 are mutually exclusive.
-c
config-file
Use config-file as the configuration
file instead of the default, /etc/lwresd.conf. -c can not be used with
-C.
-C
config-file
Use config-file as the configuration
file instead of the default, /etc/resolv.conf. -C can not be used with
-c.
-d
debug-level
Set the daemon's debug level to
debug-level. Debugging traces from lwresd become more verbose as
the debug level increases.
-f
Run the server in the foreground (i.e. do not
daemonize).
-g
Run the server in the foreground and force all
logging to stderr.
-i
pid-file
Use pid-file as the PID file instead of
the default, /var/run/lwresd/lwresd.pid.
-m
flag
Turn on memory usage debugging flags. Possible
flags are usage, trace, record, size, and
mctx. These correspond to the ISC_MEM_DEBUGXXXX flags described in
<isc/mem.h>.
-n
#cpus
Create #cpus worker threads to take
advantage of multiple CPUs. If not specified, lwresd 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.
-P
port
Listen for lightweight resolver queries on
port port. If not specified, the default is port 921.
-p
port
Send DNS lookups to port port. 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.
-s
Write memory usage statistics to stdout on
exit.
Note
This option is mainly of interest to BIND 9 developers and may be removed or
changed in a future release.
-t
directory
Chroot to
directory after processing
the command line arguments, but before reading the configuration file.
Warning
This option should be used in conjunction with the
-u option, as
chrooting a process running as root doesn't enhance security on most systems;
the way
chroot(2) is defined allows a process with root privileges to
escape a chroot jail.
-u
user
Setuid to user after completing
privileged operations, such as creating sockets that listen on privileged
ports.
-v
Report the version number and exit.
FILES
/etc/resolv.conf
The default configuration file.
/var/run/lwresd.pid
The default process-id file.
SEE ALSO
named(8),
lwres(3),
resolver(5).
AUTHOR
Internet Systems Consortium, Inc.
COPYRIGHT
Copyright © 2004, 2005, 2007-2009, 2014-2016 Internet Systems Consortium,
Inc. ("ISC")
Copyright © 2000, 2001 Internet Software Consortium.