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.
AUTHOR¶
Internet Systems Consortium, Inc.
COPYRIGHT¶
Copyright © 2000, 2001, 2004, 2005, 2007-2009, 2014-2021
Internet Systems Consortium, Inc. ("ISC")