Dynamic DNS - ArchWiki

Jump to content

# Dynamic DNS

From ArchWiki

According to Wikipedia:

  Dynamic DNS (DDNS or DynDNS) is a method of automatically updating a name server in the Domain Name System (DNS), often in real time, with the active DDNS configuration of its configured hostnames, addresses or other information.

  The term is used to describe two different concepts. The first is "dynamic DNS updating" which refers to systems that are used to update traditional DNS records without manual editing. These mechanisms are explained in RFC 2136, and use the TSIG mechanism to provide security. The second kind of dynamic DNS permits lightweight and immediate updates often using an update client, which do not use the RFC2136 standard for updating DNS records. These clients provide a persistent addressing method for devices that change their location, configuration or IP address frequently.

For RFC2136 there is nsupdate(1) from bind. For dynamic DNS services there are several packages available, see #Update clients.

## 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 will not have Internet anyway).

## Update clients

Note that some dynamic DNS providers do not require a dedicated client and can be updated with cURL.

### Multi-service clients

- ddclient — Update dynamic DNS entries for accounts on many dynamic DNS services.

  https://github.com/ddclient/ddclient || ddclient

- inadyn — Dynamic DNS client with SSL/TLS support.

  https://troglobit.com/projects/inadyn/ || inadyn

- inadyn-mt — A small and simple dynamic DNS client based on inadyn.

  https://inadyn-mt.sourceforge.net/ || inadyn-mtAUR

- ndyndns — Supports DynDNS and Namecheap.

  https://github.com/niklata/ndyndns || ndyndnsAUR

### Single-service clients

- duckdns — Update your DuckDNS.org entries from your computer with systemd.

  https://www.duckdns.org/ || duckdnsAUR, duckdns-ipv6AUR

- hetzner_ddns — Dynamic DNS daemon for Hetzner DNS

  https://github.com/filiparag/hetzner_ddns || hetzner_ddnsAUR

- noip — Dynamic DNS Client Updater for no-ip.com services.

  https://www.no-ip.com/downloads.php?page=linux || noipAUR

### 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 configuration file `/etc/ddclient/ddclient.conf` to set up your DDNS provider (it includes many examples). Then enable and start `ddclient.service`.

The configuration can be tested by running `ddclient` with the `-noquiet` and `-debug` options:

    # ddclient -daemon=0 -noquiet -debug

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

ddclient compatible services
Service | Configuration notes
--- | ---
Now-DNS | example
ChangeIP | example
Duck DNS | example
FreeDNS | example
No-IP | Use protocol `noip`, server `dynupdate.no-ip.com`
nsupdate.info | Use protocol `dyndns2`
Dyn DNS | example
Namecheap | example
Dynu | 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 checkip.dyndns.org. This address is used by default when `use=web` is specified. It is also recommended to increase the check interval to avoid frequent requests to the IP check service:

    /etc/ddclient/ddclient.conf

    daemon=900
    # obtain IP address from web status page
    use=web

An alternative IP check service can be specified with the `web` key:

    /etc/ddclient/ddclient.conf

    daemon=900
    # obtain IP address from web status page
    use=web, web=myonlineportal.net/checkip

#### Use a local script to determine IPv6 address

ddclient often gets the wrong IPv6 address or none at all, but instead of an external website the IPv6 address can be determined locally. This script can be used:

    /usr/local/bin/get-ip

    #!/bin/sh
    ip -6 -o addr show scope global | awk -F '[ \t]+|/' '$4 ~ /^[23]/ {print $4}'

Make the script executable and tell ddclient to use it:

    /etc/ddclient/ddclient.conf

    # obtain IP address from script
    usev6=cmdv6,cmdv6='/usr/local/bin/get-ip'

#### Use UPnP or NAT-PMP to determine external IPv4 address

If your router supports UPnP, install miniupnpc and use the external-ip utility:

    /etc/ddclient/ddclient.conf

    # obtain IP address from script
    usev4=cmdv4,cmdv4='/usr/bin/external-ip'

For NAT-PMP, install libnatpmp and create a script wrapping the `natpmpc` output.

    /usr/local/bin/get-ip

    #!/bin/sh
    natpmpc | grep -oP 'Public IP address : \K\S+'

Make the script executable and tell ddclient to use it:

    /etc/ddclient/ddclient.conf

    # obtain IP address from script
    usev4=cmdv4,cmdv4='/usr/local/bin/get-ip'

## Other providers

Other 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.

Category:

- Domain Name System

Dynamic DNS
Add topic