Dynamic DNS

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Revision as of 20:05, 25 February 2018 by Cbt (talk | contribs) (correction of outdated information for Now-DNS)
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Dynamic DNS or DDNS is a method of updating, in real time, a DNS to point to a changing IP address on the Internet. This is used to provide a persistent domain name for a resource lacking a static IP. To use DDNS, you need to both sign up with a DDNS provider and set up an automatic update tool that will notify the provider when your IP address changes.

Update tools


If the device needing DDNS sits behind a router, you should first check if the router itself can update any DDNS services. Although the selection of services may be limited, there are several advantages to using the router: it will probably be easier to set up, will require little to no maintenance, and will have no downtime (if the router is down you won't have Internet anyway).


ddclient is compatible with many DDNS services and is the recommended tool for updating DDNS if your router is not an option. It includes systemd support.

After installing, edit the default config /etc/ddclient/ddclient.conf to set up your DDNS provider (it includes many examples). Then enable and start ddclient.service.

Some of the compatible services are listed below, but you can also check the examples and protocols for more.

ddclient compatible services
Service Cost Available Records Hostname Limit Config Notes Alternative tools
Now-DNS Free A, AAAA unlimited example
ChangeIP Free or paid A, AAAA, CNAME, MX, codomains 7 free example
DNSdynamic Free example
Duck DNS Free example duckdnsAUR
FreeDNS Free or paid CNAME, A, AAAA, MX, NS, TXT, LOC, RP, HINFO, SRV 5 free example afraid-dyndns-uvAUR, petrifiedAUR
No-IP Free or paid 3 free, 25+ paid Use protocol noip, server dynupdate.no-ip.com noipAUR
nsupdate.info Free and open source A, AAAA Use protocol dyndns2 inadyn-forkAUR
Dyn DNS Free or paid A, CNAME, MX example ndyndnsAUR
Namecheap Paid A, CNAME example ndyndnsAUR
Dynu Free or paid 4 free, 500 paid example
Note: Free users of no-ip are required to manually confirm their domain(s) every 30 days. Domain confirmation is not required for Enhanced users though. More info at Why is My Hostname Pending Deletion?

Use an external website to determine IP address

If ddclient is unable to detect your IP address, you can configure ddclient to fetch your IP from an external webpage such as whatismyip.org. Add somewhere in the config file:

# use whatismyip.org to determine IP address

Starting ddclient after networking is up

If you find that ddclient is unable to update your IP properly, it may be that the ddclient process is starting before networking is up. To fix it, you can edit the unit file to depend on network-online.target:

# systemctl edit ddclient.service

Additional configuration for network-online.target may be necessary, see [1].

Other tools

Other DDNS updaters that work with several providers are inadyn-mtAUR (supported providers) and ndyndnsAUR (supports DynDNS and Namecheap).

Other providers

The following DDNS providers are not compatible with ddclient so updating your IP with them may require a special tool or some custom scripting. Remember that if the service allows you to update your IP using the command line, you can automate the process using tools such as cron or systemd/Timers.


Duiadns.org is a free service.


FreeDns.io provides free A and AAAA DNS records and CNAME, TXT and MX records with a premium membership. You can update your IP using their HTTP API (with a 60 requests-per-hour limit). They provide several example scripts.


Now-DNS.com is a free service which is easy and uncomplicated to set up.


System-NS is a free service which can be updated via the command line. See the official documentation.


If you use loopia.se as name server, you can query updates of DNS records via curl as described in the official documentation.

If you use 2FA for login, or by some other reason would rather use the LoopiaAPI via a python script to change the DNS dynamically, you should follow the instructions on this page. The python file is well written and easy to understand, and basically all you need to do is to generate an API key on your login at Loopia kundzon first.