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 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.
config-file
Use config-file as the
configuration file instead of the default,
/etc/resolv.conf.
debug-level
Set the daemon's debug level to debug-level.
Debugging traces from lwresd become
more verbose as the debug level increases.
Run the server in the foreground (i.e. do not daemonize).
Run the server in the foreground and force all logging
to stderr.
#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.
port
Listen for lightweight resolver queries on port
port. If
not specified, the default is port 921.
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.
Write memory usage statistics to stdout
on exit.
This option is mainly of interest to BIND 9 developers and may be removed or changed in a future release.
directory
chroot() to directory after
processing the command line arguments, but before
reading the configuration file.
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.
user
setuid() to user after completing
privileged operations, such as creating sockets that
listen on privileged ports.
Report the version number and exit.