lwresd - lightweight resolver daemon
lwresd [ -C config-file ] [ -d debug-level ] [ -f ] [ -g ] [ -i pid-file ] [ -n #cpus
] [ -P port ] [ -p port ] [ -s ] [ -t directory ] [ -u user ] [ -v ]
lwresd is the daemon providing name lookup services to clients that use the BIND 9 light-
weight 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 proto-
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
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
Use config-file as the configuration file instead of the default, /etc/resolv.conf.
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.
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
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 pro-
vides a way of testing the lightweight resolver daemon with a name server that lis-
tens 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 arguments, but before read-
ing 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 Software Consortium
BIND9 June 30, 2000 LWRESD(8)