Man Linux: Main Page and Category List


       dyndns - Update IP address to dynamic DNS (DDNS) provider


           dyndns --login LOGIN --password PASSWORD \

       Note: By Default this program expects provider. If you
       use other provider, see option --provider


       A Perl client for updating dynamic DNS IP information at supported
       providers (see "--provider").

       The dynamic DNS services allow mapping a dynamic IP address to a static
       hostname. This way the host can be refered by name instead of the
       changing IP address from the ISP’s pool. Some DDNS providers offer a
       single account and a single host namefree of charge. Please check the
       information from the Providers’ pages.

       Separate files are used for remembering the last IP address to prevent
       updating the same IP address again. This is necessary in order to
       comply guidelines of the providers where multiple updates of the same
       IP address could cause your domain to be blocked. You should not
       normally need to touch the files where the ip addresses are stored.

       If you know what you are doing and desperately need a forced update,
       delete the IP files and start program with apropriate arguments.
       Without the information about previous IP address, program sends a new
       update request to the provider.

       Program has been designed to work under any version of Windows or
       Linux, possibly Mac OS included. It may not work under other Unix/BSD
       variants. Please see BUGS section how to provide details to add support
       for other operating systems.

       Visit the page of the provider and create an account. Write down the
       login name, password and host name you registered.

       For Windows operating systems, you need to install Perl. There are two
       Perl incarnatons: Native Windows version (Activestate Perl) and Cygwin
       version. The "" is recommended as it more closely
       follows the original Perl environment.


   Gneneral options
       --config=FILE [--config=FILE ...]
           List of configuration files to read. No command line options other
           than --verbose, --debug or --test should be appended or results are
           undefined. Each file must contain complete DDNS account

           The FILE part will go through Perl’s "glob()" function, meaning
           that the filenames are expanded. Series of configuration files can
           be run at once e.g. within directory "/etc/dyndns/" by using a
           single option. The order of the files processed is alphabetical:


           See section CONFIGURATION FILE for more information how to write
           the files.

       --host=host1 [--host=host2 ...]
           Use registered HOST(s).

       --group GROUP
           This option is only for --provider noip

           Assign IP to GROUP. Do you have many hosts that all update to the
           same IP address? Update a group instead of a many hosts.

       --login LOGIN
           DDNS account’s LOGIN name.

       --mxhost MX-HOST-NAME
           This option is only for --provider dyndns

           Update account information with MX hostname. Specifies a Mail
           eXchanger for use with the host being modified. Must resolve to an
           static IP address, or it will be ignored. If you don’t know DNS,
           don’t touch this option.

           The servers you list need to be correctly configured to accept mail
           for your hostname, or this will do no good. Setting up a server as
           an MX without permission of the administrator may get them angry at
           you. If someone is contacted about such an infraction, your MX
           record will be removed and possibly further action taken to prevent
           it from happening again. Any mail sent to a misconfigured server
           listed as an MX may bounce, and may be lost.

           This option is only for --provider dyndns

           Turn on MX option. Request that the MX in the previous parameter be
           set up as a backup. This means that mail will first attempt to
           deliver to your host directly, and will be delivered to the MX
           listed as a backup.

           Note regarding provider "noip":

           Update clients cannot change this value. Clients can only submit
           requests to the php script to update the A record. Changes such as
           MX records must be done through website.

           If given, set the host to offline mode.

           "Note:" [dyndns] This feature is only available to donators. The
           "!donator" return message will appear if this is set on a non-
           donator host.

           This is useful if you will be going offline for an extended period
           of time. If someone else gets your old IP your users will not go to
           your old IP address.

       --password PASSWORD
           DDNS account’s PASSWORD.

       --system {dyndns|statdns|custom}
           This option is only for --provider dyndns

           The system you wish to use for this update. "dyndns" will update a
           dynamic host, "custom" will update a MyDynDNS Custom DNS host and
           "statdns" will update a static host. The default value is "dyndns"
           and you cannot use other options (statdns|custom) unless you donate
           and gain access to the more advanced features.

           See the DDNS provider’s pages for more information.

           Turn on wildcard option. The wildcard aliases
           "*.yourhost.ourdomain.ext" to the same address as

   Additional options
       -D, --daemon [WAIT-MINUTES]
           Enter daemon mode. The term "daemon" refers to a standalone
           processes which keep serving until killed. In daemon mode program
           enters into infinite loop where IP address changes are checked
           periodically. For each new ip address check, program waits for
           WAIT-MINUTES. Messages in this mode are reported using syslog(3);
           if available.

           This option is designed to be used in systems that do not provide
           Unix-like cron capabilities (e.g under Windows OS). It is better to
           use cron(8) and define an entry using crontab(5) notation to run
           the update in periodic intervals. This will use less memory when
           Perl is not permanently kept in memory like it would with option

           The update to DDNS provider happens only if

               1) IP address changes
               2) or it has taken 30 days since last update.
                  (See DDNS providers' account expiration time documentation)

           The minimum sleep time is 5 minutes. Program will not allow faster
           wake up times(*). The value can be expressed in formats:

               15      Plain number, minutes
               15m     (m)inutes. Same sa above
               1h      (h)ours
               1d      (d)days

           This options is primarily for permanent Internet connection. If you
           have a dial-up connection, it is better to arrange the IP update at
           the same time as when the connection is started. In Linux this
           would happen during ifup(1).

           (*) Perl language is CPU intensive so any faster check would put
           considerable strain on system resources. Normally a value of 30 or
           60 minutes will work fine in most cases. Monitor the ISP’s IP
           rotation time to adjust the time in to use sufficiently long wake
           up times.

       --ethernet [CARD]
           In Linux system, the automatic IP detection uses program
           ifconfig(1). If you have multiple network cards, select the correct
           card with this option. The default device used for query is "eth0".

       --file PREFIX
           Prefix where to save IP information. This can be a) a absolute path
           name to a file b) directory where to save or c) directory + prefix
           where to save.  Make sure that files in this location do not get
           deleted. If they are deleted and you happen to update SAME ip twice
           within a short period - according to FAQ - your
           address may be blocked.

           On Windows platform all filenames must use forward slashs like
           "C:/somedir/to/", not "C:\somedir\to\".

           The PREFIX is only used as a basename for supported DDNS accounts
           (see --provider). The saved filename is constructed like this:

                                     See option --system

           A sample filename in Linux could be something like this if PREFIX
           were set to "/var/log/dyndns/":


       -f, --file-default
           Use reasonable default for saved IP file PREFIX (see --file). Under
           Windows, %WINDIR% is used. Under Linux the PREFIXes searched are

               /var/log/dyndns/     (if directory exists)
               /var/log/            (system's standard)
               $HOME/tmp or $HOME   if process is not running under root

       --proxy HOST
           Use HOST as outgoing HTTP proxy.

       -P, --provider TYPE
           By default, program connects to "" to update the dynamic
           IP address. There are many free dynamic DNS providers are reported.
           Supported list of TYPES in alphabetical order:

               hnorg       No domain name limists
                           Basic DDNS service is free (as of 2003-10-02)

               dyndns      No domain name limits.
                           Basic DDNS service is free (as of 2003-10-02)
                           See also

               noip        No domain name limits.
                           Basic DDNS service is free (as of 2003-10-02)

           NOTE: as of 2010, the support for sites of hnorg, noip is probably
           non-working due to changes in the interfaces. Please use only
           dyndns at this time.

           Query current IP address and quit. Note: if you use router, you may
           need --urlping* option, otherwise the IP address returned is your
           subnet’s DHCP IP and not the ISP’s Internet IP.

           Output of the command is at least two string. The second string is
           "last-ip-info-not-available" if the saved ip file name is not
           specified.  In order to program to know where to look for saved IP
           files you need to give some --file* or --config option. The second
           string can also be "nochange" if current IP address is same as what
           was found from saved file. Examples:

      nochange 18
                                    How many days since last saved IP

           Note for tool developers: additional information may be provided in
           future. Don’t rely on the count of the output words, but instead
           parse output from left to right.

       --query-ipchanged [exitcode]
           Print message if IP has changed or not. This option can take an
           optional string argument "exitcode" which causes program to
           indicate changed ip address with standard shell status code (in
           bash shell that would available at variable $?):

               $ dyndns --query-ipchange exitcode --file-default \
                 --provider dyndns --host
               $ echo $?

               ... the status code of shell ($?) would be:

               0   true value, changed
               1   false value, error code, i.e. not changed

           Without the "exitcode" argument, the returned strings are:

                           Current IP address
               changed  35 111.222.333.444
               nochange 18
                        Days since last IP update. Based on saved IP file's
                        time stamp.

           If the last saved IP file’s time stamp is too old, then even if the
           IP were not really changed, the situation is reported with word
           "changed". This is due to time limits the DDNS providers have. The
           account would expire unless it is updated in NN days.

           Note for tool developers: additional information may be provided in
           future. Don’t rely on the count of the output words, but instead
           parse output from left to right.

           Print the name of the IP file and quit.

           Note: In order for this option to work, you must supply all other
           options would be normally pass to update the DDNS account, because
           the Ip filename depends on these options. Alternatively provide
           option --config FILE from where all relevant information if read.

               --ethernet      [optional, defaults to eth0]
               --provider      [optional, defaults to dyndns]
               --system        [optional, defaults to dyndns]
               --host          required.

           Here is an example which supposed that directory "/var/log/dyndns/"
           already exists:

               $ dyndns --file-default --query-ipfile \
                 --provider dyndns --host

       --regexp REGEXP
           In host, which has multiple netword cards, the response can include
           multiple IP addresses. The default is to pick always the first
           choice, but that may not be what is wanted. The regexp MUST not
           contain capturing parentheses: if you need one, use non-capturing
           choice (?:). Refer to Perl manual page "perlre" for more
           information about non-cpaturing regular expression parentheses.

           Here is an example from Windows:

               Ethernet adapter {3C317757-AEE8-4DA7-9B68-C67B4D344103}:

                   Connection-specific DNS Suffix  . :
                   Autoconfiguration IP Address. . . :
                   Subnet Mask . . . . . . . . . . . :
                   Default Gateway . . . . . . . . . :

               Ethernet adapter Local Area Connection 3:

                   Connection-specific DNS Suffix  . :
                   IP Address. . . . . . . . . . . . :
                   Subnet Mask . . . . . . . . . . . :
                   Default Gateway . . . . . . . . . :

           The is the intended dynamic IP address, not the first
           one.  To instruct searching from somewhere else in the listing,
           supply a regular expressions that can match a portion in the
           listing after which the IP address appears. In the above case, the
           regexp could be:

               --regexp "Connection 3:"

           In Windows, the words that follow "IP Address" are automatically
           expected, so you should not add them to the regexp.

           In FreeBSD 4.5, you may get following response:

               tun0: flags <UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1492
                   inet6 fe80::250:4ff:feef:7998%tun0 prefixlen 64 scopeid 0x7
                   inet --> netmask 0xffffffff
                   inet --> netmask 0xffffffff
                   inet --> netmask 0xffffffff
                   inet --> netmask 0xff000000
                   Opened by PID 64

           The correct IP address to pick from the listing is the one, which
           does not contain netmask 0xffffffff. The picked address for above
           is therefore The regexp that finds that line is:

               --regexp ".*0xffffffff.*?inet"
                          |            |
                          |            Search minimum match until word "inet"
                          search maximum match

           This will match all the way until the the last line with netmask
           0xffffffff, after which shortest match ".*?" to "inet" is reached
           to read the number following it. The regexp must make sure that the
           next word after its match point is the wanted address.

   Cable, DSL and router options
       If you do not have direct access to world known "real" IP address, but
       to a subnet IP address, then you cannot determine your outside world IP
       address from your machine directly. See picture below:

                               router/subnet                    Internet
                              +-------------+                +-----------+
          Your PC:            |             | maps address   |           |
          connect to ISP -->  | ROUTER      | -------------> |           |
                              | 192.168.... |                |  |
          local ip says:      +-------------+                +-----------+
                                    THE REAL IP

       ASDL and cable modem and other connections may not be directly
       connected to Internet, but to a router to allow subnnetting internal
       hosts. This makes several computers to access the Internet while the
       ISP has offered only one visible IP address to you. The router makes
       the mapping of the local subnet IP to the world known IP address,
       provided by the ISP when the connection was established.

       You need some way to find out what is the real IP is. The simplest way
       is to connect to a some web page, which runs a reverse lookup service
       which can show the connecting IP address.

       Note: the following web web page does not exists. To find a service
       that is able to display your IP address, do a google search. Let’s say,
       that you found a fictional service "" and
       somewhere in the web page it reads:

               Your IP address is:

       This is what you need. To automate the lookup from web page, you need
       to instruct the program to connect to URL page and tell how to read the
       ip from page by using a regular expression. Consult Perl’s manual page
       "perlre" if you are unfamiliar with the regular expressions. For the
       above fictional service, the options needed would be:

           --urlping         ""
           --urlping-regexp  "address is:\s+([\d.]+)"
                                         |  ||
                                         |  |+- Read all digits and periods
                                         |  |
                                         |  +- capturing parentheses
                                         +- expect any number of whitespaces

       NOTE: The text to match from web page is not text/plain, but text/html,
       so you must look at the HTML page’s sources to match the IP address
       correctly without the bold <b> tags etc.

       --urlping URL
           Web page where world known IP address can be read. If you find a
           Web server that is running some program, which can show your IP
           addres, use it. The example below connects to site and calls CGI
           program to make show the connector’s IP address. Be polite. Making
           calls like this too often may cause putting blocks to your site.


           Be sure to use period of 60 minutes or more with --daemon option to
           not increase the load in the "ping" site and cause admin’s to shut
           down the service.

           Contact service to obtain IP address
           information. This is shorthand to more general optiopn --urlping.

       --urlping-linksys [TYPE]
           Specialized router option for Linksys products.

           This option connects to Linksys Wireless LAN 4-point router, whose
           page is by default at local network address
           -<>. The world known IP address (which
           is provided by ISP) is parsed from that page. The product is
           typically connected to the cable or DSL modem. Refer to routing
           picture presented previously.

           If the default login and password has been changed, options
           --urlping-login and --urlping-password must be supplied

           For TYPE information, See <>. Products codes
           currently supported include:

            - BEFW11S4, Wireless Access Point Router with 4-Port Switch.
            - WRT54GL, Wireless WRT54GL Wireless-G Broadband Router.

       --urlping-login LOGIN
           If "--urlping" web page requires authentication, supply user name
           for a secured web page.

       --urlping-password LOGIN
           If "--urlping" web page requires authentication, supply password
           for a secured web page.

       --urlping-regexp REGEXP
           After connecting to page with --urlping URL, the web page is
           examined for REGEXP. The regexp must catch the IP to perl match $1.
           Use non-capturing parenthesis to control the match as needed. For
           example this is incorrect:

               --urlping-regexp "(Address|addr:)\s+([0-9.]+)"
                                 |                 |
                                 $1                $2

           The match MUST be in "$1", so you must use non-capturing perl
           paentheses for the first one:

               --urlping-regexp "(?:Address|addr:) +([0-9.]+)"
                                  |                 |
                                  non-capturing     $1

           If this option is not given, the default value is to find first
           word that matches:


   Miscellaneous options
       --debug [LEVEL]
           Turn on debug with optional positive LEVEL. Use this if you want to
           know details how the program initiates connection or if you
           experience trouble contacting DDNS provider.

           Print help

           Print help in HTML format.

           Print help page in Unix manual page format. You want to feed this
           output to nroff -man in order to read it.

       --test [LEVEL]
           Run in test mode, do not actually update anything. LEVEL 1 allows
           sending HTTP ping options and getting answers.

           This is for developer only. Run internal integrity tests.

           This is for developer only. Uses DYNDNS test account options. All
           command line values that set host information or provider are
           ignored. Refer to client page at

           Print informational messages.

           Print version and contact information.


       To check current IP address:

         dyndns --query [--urlping...]
                        Select correct option to do the "ping" for IP

       Show where the ip file is/would be stored with given connect options.
       The option --file-default uses OS’s default directory structure.

         dyndns --file-default --query-ipfile --provider dyndns \

       To upate account information to DDNS provider:

         dyndns --provider dyndns --login <login> --password <pass> --host

       If your router can display a web page containing the world known IP
       address, you can instruct to "ping" it. Suppose that router is at
       address and page that displays the world known IP is
       "status.html", and you have to log in to the router using username
       "foo" and password "bar":

         dyndns --urlping \
                --urlping-login foo                      \
                --urlping-pass  bar                      \

       If the default regexp does not find IP address from the page, supply
       your own match with option --urlping-regexp. In case of doubt, add
       option --debug 1 and examine the responses. In serious doubt, contact
       the maintainer (see option --version) and send the full debug output.

       Tip: if you run a local web server, provider "" can
       direct calls to it. See option "--wildcard" to enable
       ‘*’ domain delegation, like if it we accessed using


       Instead of supplying options at command line, the options can be stored
       to configuration files. For each DDNS account and different domains, a
       separate configuration file must be created. The configuration files
       are read with option --config.

       The syntax of the configuration file includes comments that start with
       (#).  Anything after hash-sign is interpreted as comment. Values are
       set in KEY = VALUE fashion, where spaces are non-significant. Keys are
       not case sensitive, but values are.

       Below, lines marked with [default] need only be set if the default
       value needs to be changed. Lines marked with [noip] or [dyndns] apply
       to only those providers’ DDNS accounts. Notice that some keys, like
       "host", can take multple values seprated by colons. On/Off options take
       values [1/0] respectively. All host name values below are fictional.

           # /etc/dyndns/dyndns.conf

           #  Set to "yes" to make this configuration file excluded
           #  from updates.

           disable  = no       # [default]

           ethernet = eth0     # [default]
           group    = mygourp  # [noip]
           host     =,

           #   If you route mail. See documentation for details
           #   how to set up MX records. If you know nothing about DNS/BIND
           #   Don't even consider using this option. Misuse or broken
           #   DNS at your end will probably terminate your 'free' dyndns contract.

           mxhost   =

           #   Details how to get the world known IP address, in case the standard
           #   Linux 'ifconfig' or Windows 'ipconfig' programs cannot be used. This
           #   interests mainly Cable, DSL and router owners. NOTE: You may
           #   not use all these options. E.g. [urlping-linksys4] is alternate
           #   to [urlping] etc. See documentation.

           urlping-linksys  = BEFW11S4
           urlping-login    = joe
           urlping-password = mypass

           urlping          =
           urlping-regexp   = (Address|addr:)\s+([0-9.]+)

           #   Where IPs are stored. Directory name or Directory name with
           #   additional file prefix. The directory part must exist. You could
           #   say 'file = /var/log/dyndns/' but that's the default.

           file     = default              # Use OS's default location

           #   The DDNS account details

           login    = mylogin
           password = mypass
           provider = dyndns               # [default]
           proxy    =    # set only if needed for HTTP calls

           #   Hou need this option only if you have multiple ethernet cards.
           #   After which regexp the IP number appers in ifconfig(1) listing?

           regexp   = .*0xffffffff.*?inet

           #   What account are you using? Select 'dyndns|statdns|custom'

           system   = dyndns               # Provider [dyndns] only

           #   Yes, delegate all * calls

           wildcard = 1

           # End of cnfiguration file

       See the details of all of these options from the corresponding command
       line option descriptions. E.g. option ’ethernet’ in configuration file
       corresponds to --ethernet command line option. The normal configuration
       file for average user would only include few lines:

           #   /etc/dyndns/

           host             =
           file             = default      # Use OS's default location
           login            = mylogin
           password         = mypassword
           provider         = dyndns
           system           = dyndns       # or 'statdns'
           wildcard         = 1            # Delegate *

           # End of cnfiguration file

       TODO (write Debian daemon scripts) FIXME:

           update-rc.d dyndns start 3 4 5 6    # Debian


       For new Operating System, provide all relevant commands, their options,
       examples and their output which answer to following questions. The
       items in parentheses are examples from Linux:

           - How is the OS detected? Send result of 'id -a', or if file/dir
             structure can be used to detect the system. In Lunux the
             existence of /boot/vmlinuz could indicate that "this is a Linux
           - What is the command to get network information (commandlike 'ifconfig')
           - Where are the system configuration files stored (in directory /etc?)
           - Where are the log files stored (under /var/log?)

       To add support for routers that can be connected through HTTP protocol
       or with some other commands, please provide connection details and full
       HTTP response:

         lynx -dump


       1. Turn on --debug to see exact details how the program runs and what
       HTTP requests are sent and received.

       2. Most of the <--query> options can’t be used standalone. Please see
       documentation what additional options you need to supply with them.


           Directory of temporary files. Defaults to system temporary dir.


       Daemon startup file


       In Linux the syslog message files are:

           /etc/syslog.conf         daemon.err daemon.warning

       There is no default location where program would search for
       configuration files. At installation, configuration examples are put in
       directory "/etc/dyndns/examples". It is recommended that the examples
       are modified and copied one directorory up in order to use option
       --config /etc/dyndns/*.

       If program is run with Windows Activestate Perl, the log file is stored
       to file "C:/syslog.txt".


       syslog(3), Debian package ddclient(1)

       See other clients at


   Cygwin syslog
       There is no syslog daemon in Cygwin. The Cygwin POSIX emulation layer
       takes care about syslog requests. On NT and above systems it logs to
       the Windows’s event manager, on Win9x and ME a file is created in the
       root of drive "C:". See message
       <> for more details.

       You can see the entries in W2K Start => Settings => Administrative
       Tools => Computer Management: [ System Tools / Event Viewer /
       Application ]

   Debugging errors
       Please use option --debug 2 and save the result. Contact maintainer if
       you find bugs or need new features.

   About providers hnorg and noip
       The program is primarily developed and maintained to support  The other providers haven’t been tested since 2003.



       The client specification is at


       "CPAN/Administrative" "CPAN/Networking"


       HTTP::Headers HTTP::Request::Common LWP::UserAgent LWP::Simple






       Copyright (C) 1999-2009 Jari Aalto. All rights reserved. This program
       is free software; you can redistribute and/or modify program under the
       terms of GNU General Public license v2 or later.

       This documentation may be distributed subject to the terms and
       conditions set forth in GNU General Public License v2 or later (GNU
       GPL); or, at your option, distributed under the terms of GNU Free
       Documentation License version 1.2 or later (GNU FDL).