lwresd - lightweight resolver daemon
lwresd [ -C config-file ] [ -d debug-level ] [ -f ] [ -g ] [ -i
pid-file ] [ -n #cpus ] [ -P port ] [ -p port ] [ -s ] [ -t direc-
tory ] [ -u user ] [ -v ]
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 pro-
cesses 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 com-
pletes, 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.
Use config-file as the configuration file instead of the
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
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
Listen for lightweight resolver queries on port port. If not
specified, the default is port 921.
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.
chroot() to directory after processing the command line argu-
ments, 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() is defined allows a
process with root privileges to escape a chroot jail.
setuid() to user after completing privileged operations, such as
creating sockets that listen on privileged ports.
-v Report the version number and exit.
The default configuration file.
The default process-id file.
named(8), lwres(3), resolver(5).
Internet Systems Consortium
BIND9 June 30, 2000 LWRESD(8)
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