Here is a brief introduction to using the client on a unice.
It is part of an email I sent answering a user's questions.


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        Grab the client software for ddns.nu, that is a good start, if
nothing else, you can run it manually until you work out were to hook it
into your config.

        On the average linux box this should grab and compile it: 

nexus:~$ cd /tmp
nexus:/tmp$ lynx -dump http://www.ddns.nu/files/ddns3-client.tar.gz > 
ddns3-client.tar.gz
nexus:/tmp$ tar -xzf ddns3-client.tar.gz
nexus:/tmp$ cd ddns3-client
nexus:/tmp/ddns3-client$ make
gcc -Wall -O6  -c sockio.c -o sockio.o
gcc -Wall -O6  -c crypto.c -o crypto.o
gcc -Wall -O6  -c auth.c -o auth.o
gcc -Wall -O6  -c md5.c -o md5.o
gcc -Wall -O6  -c ctx.c -o ctx.o
ar -csr libddns3.a *.o
gcc -Wall -O6  -lcrypt ddns3.c libddns3.a -o ddns3
strip ddns3
        My prompt might be a little different, and the result a
different size, but you should now have a binary in current directory of
the client:

nexus:/tmp/ddns3-client$ ls -la ddns3
-rwxr-xr-x   1 alany    users       16828 Aug 15 03:44 ddns3*

        You can run it with no arguments to get usage:

nexus:/tmp/ddns3-client$ ./ddns3
        
DDNS Client v3 (c) :: http://www.ddns.nu/
(c) 2001 Alan Yates <alany@alanyates.com>

Usage: ddns3 <required args> [optional args] <action list>

Required args
        --user  username
        --pass  password
Optional args
        --host  server-hostname         specify server host
        --port  server-tcp-port         specify server port
        --debug                         activate debug mode
        --auth  auth-name               specify authentication type
Authentication types:
        plaintext, crypt, md5, ddns (default), strong
Actions:
        list                            lists IP-Handles
        set <handle> <ip>               sets an IP-Handle's value
        guess <handle> <source>         sets an IP-Handle's value
                                        guessing the IP from the <source>
                                        end of the connection, ends are
                                        named 'remote' or 'local'


        That is a lot of long winded garbage, but basically you use it
like this (password changed):
        
        Getting a list of your handles:

nexus:/tmp/ddns3-client$ ./ddns3 --user alany --pass mypass list
nexus-bpc-iface      144.132.130.202
alanyates-herf-lpb   203.32.117.232
redirect-ddns-nu     203.32.117.205
test                 203.32.117.205

        Updating a handle and viewing the change:
        
nexus:/tmp/ddns3-client$ ./ddns3 --user alany --pass mypass set test 0.0.0.0
server_message: +OK ip-handle updated, 2 ddns-record(s) updated

nexus:/tmp/ddns3-client$ ./ddns3 --user alany --pass mypass list
nexus-bpc-iface      144.132.130.202
alanyates-herf-lpb   203.32.117.232
redirect-ddns-nu     203.32.117.205
test                 0.0.0.0

        So to automate this, all you need is to install the ddns3 binary
somewhere:

nexus:/tmp/ddns3-client$ su -
Password:
nexus:~# cp /tmp/ddns3-client/ddns3 /usr/local/bin
nexus:~# chmod a+rx /usr/local/bin/ddns3

        Then the hard part, hacking your config to call it
automatically.  I'll use my office's ADSL config as an example:
        
jolt:~# cd /etc/ppp/
jolt:/etc/ppp# cat ip-up
#!/bin/sh
#
# Update dynamic DNS records
#

if [ $1 = "ppp0" ] ; then
        # ddns.nu updates
        /usr/local/bin/ddns3 --user user --pass pass set adsl-iface $4

        # more unrelated stuff...
fi
 
        Now this is cheating a little.  It may not always be ppp0 for
the ADSL interface, but in my case it always is.  You may wish to
despense with the if and fi lines completely if you don't have a
PSTN modem or other PPP device that might also call this script.
        
        That is all there is too it, you may need to create the
/etc/ppp/ip-up file and make it executable, but that is all I use and it
works just fine.

        Have a read of the pppd manpage, there is information there
about the ip-up (et al) scripts that are called by pppd, including the
order of the arguments passed to it.


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