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Dudders is a utility for updating DNS records. It points a domain name to a given IP address, using the RFC2136 DNS UPDATE protocol and a SIG(0) signature. It is designed with embedded systems in mind.

This has several implications for users:

  • you can't use it to do all the things DNS UPDATE can do,
  • it will error and exit rather than dealing with problems;
  • it will fit and work on your embedded device!

For a general purpose DNS UPDATE utility where space is not a concern, use ISC's nsupdate, which is distributed with BIND. Other free clients with similar functionality include ddclient, ez-ipupdate, updatedd, ipupdate, and dnssec-tools's ifup-dyndns.

The ISC BIND 9 Administrator Reference Manual contains instructions for configuring your zone's DNS server to support a SIG(0) update, under the DNSSEC section.

For instructions on how to invoke the program, consult the dudders(8) manual page, which is built by configure.

With some poetic license, dudders spells "Dynamically Updating DNS Duly Embracing RSA SIG(0)".


Dudders is licensed under the Apache License, Version 2.0 (the "License"); you may not use this software except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


A POSIX-like standard C library is expected, complete with resolver. The BSD, uClibc, and glibc libraries should all work.

Cryptography dependencies

An external library is required by dudders for cryptography. The following packages are supported to provide crypto libraries:

  • openssl: The OpenSSL project's libcrypto
  • gcrypt: The GnuPG spinoff crypto library libgcrypt

Specify the crypto library to use at build time by calling configure with:


Alternatively, dudders can build support for both the libraries as "plugins". By calling configure with:

--with-crypto=dl --with-dlcrypto=LIST

dudders will try to dynamically load each of the plugins using dlopen(3), in the order specified by LIST, until one works. All packages in LIST must be available at compile-time and at least one at runtime.

For each of the specified plugins, a shared library will be installed in the plugin directory (/usr/local/lib/dudders by default). To run dudders from the build directory (without running make install), you will need to add .libs in the build directory to dlopen's search paths. The mechanism for this depends on the system's implementation of dlopen, but on Linux one can run something like:


Other build options

By default, the program is built with a meagre amount of debugging information. To make it leaner, call configure with:


Consult the INSTALL file for additional instructions on building and installing dudders.


Visit the dudders homepage at