Linux Update Client: ddclient

ddclient is a Perl based client used to update DNS entries. This client works with all of our services as well as services provided by many of our competitors. ddclient was originally written by Paul Burry and is now maintained by a group of developers via a SourceForge project.

Acknowledgment: Much of the info here is extracted from the ddclient home page.

Download: The most recent version of ddclient should always be available here.

IP Detection

ddclient supports detecting the public IP address either directly from a hardware interface, from a status page provided by a NAT router, or via our CheckIP service. Due to this flexibility, ddclient can be used in almost any possible network configuration.

System Compatibility

ddclient is a Perl based script, and as such should be runnable on any system that supports Perl. Officially all “posix” style OSes are supported. This includes all Linux, Unix and BSD variants, including Mac OS X.

Configuration File

Update Client Configurator – Generate your conf file after reading how to run ddclient

Because ddclient supports multiple DDNS services, its configuration files can be fairly daunting. To help alleviate that, we’re providing stripped down ddclient.conf files which are restricted to just those services which we support.

Here is a basic template which provides the various options available.

# check every 600 seconds
# log update msgs to syslog
# mail all msgs to root
# mail failed update msgs to root
# record PID in file.
# Cache file
### Select one of these options to determine your IP address
## via hardware interface (if you don't have a router/firewall)
#use=if, if=eth0
## via our CheckIP server
#use=web,, web-skip='IP Address'
## from the status page for a linksys router/firewall
#use=linksys, fw=linksys, fw-login=admin, fw-password=admin
## from a FW status page
#fw-login=admin, fw-password=XXXXXX
#use=fw, fw=, fw-skip='IP Address'
## Enter your Dyn username and password here
# your Dyn username
# your Dyn password
## This section requires no changes unless you need to set a default proxy server
## or you need to bypass your proxy server (because it interferes with the updates)
# default protocol
# default server
# default server (bypassing proxies)
# default proxy
## Default options for Dynamic/Static DNS Hosts
# default MX host (leave undefined by default)
# MX host is primary MX? (leave undefined by default)
# add wildcard CNAME?
## Dynamic DNS hosts go here,
## Static DNS hosts go here
## Dyn Standard DNS hosts go here

Here is a minimal ddclient.conf file designed to update a single Dynamic DNS host plus a single Dyn Standard DNS host and using our CheckIP service to get the IP address:

# Basic configuration file for ddclient
# /etc/ddclient.conf
use=web,, web-skip='IP Address'

Here is a third example which shows ddclient configured to get it’s IP address from the status page provided by a router. Note that here we’ve set the daemon sleep period to 60 seconds (the smallest value ddclient accept as a sleep value).

# Basic configuration file for ddclient
# /etc/ddclient.conf
use=linksys, fw=linksys, fw-login=admin, fw-password=admin

Secure Updates

Since 3.7.0, ddclient support ssl updates. To use ssl, put “ssl=yes” in your configuration and make sure you have IO::Socket::SSL.

# Basic HTTPS configuration file for ddclient
# /etc/ddclient.conf
use=web,, web-skip='IP Address'

On debian, you need libio-socket-ssl-perl to have IO::Socket::SSL

Issues To Be Aware Of

  1. The DynDNS update protocol supports values of “NOCHG” for the MX,
    BACKMX, and WILDCARD options, but ddclient does not support these
    values. Entering these values in the ddclient.conf file will result in
    ddclient not setting those options in the update command at all.
  2. The DynDNS protocol specification has the option as BACKMX, but in the
    ddclient.conf file this is specified using the option “BACKUPMX”.
    ddclient does send the correct parameter in the update command, you
    just need to be sure to use the ddclient version of the option in the
    config file.
  3. ddclient can be run either daemon mode, or as a single shot update
    fired off from crontab or other similar process. When using it in
    conjunction with CheckIP or monitoring a hardware interface you should
    always run it in daemon mode.

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