Dynamic 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

Router

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

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 Use protocol dyndns2, server now-dns.com/update
ChangeIP Free or paid A, AAAA, CNAME, MX, codomains 7 free
DNSdynamic Free example
Duck DNS Free 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
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:

/etc/ddclient/ddclient.conf
# use whatismyip.org to determine IP address
use=web
web=whatismyip.org

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
[Unit]
After=network-online.target
Wants=network-online.target

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

Duiadns.org is a free service which can be automated with duiadnsAUR[broken link: archived in aur-mirror].

FreeDns.io

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

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

System-NS

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