My ISP, like most of the others in France, only assigns dynamic IP addresses to its customers: this means that the IP address is likely to change at any time, especially when my box is updated or rebooted. Most of the time, the possibility to have a fixed IP address is an option, reserved for expensive offers.
For most users, this does not present any practical problems. However, the situation becomes more complicated when you want to self-host sites or services that are intended to be accessible from the outside: how can you associate a domain name with a machine whose IP address can change at any time?
This is the principle of dynamic DNS: you install on your machine a small software that regularly checks the current IP address, and as soon as it changes, sends it to your provider to update the DNS zone accordingly.
This article shows how to do this with OVH and a Raspberry Pi running Raspbian.
Configuration on the OVH side
This part assumes that the domain name is managed by OVH, and that no record exists in the DNS zone for the domain name or subdomain that will point to our machine.
Creation of a DynHost identifier.
The first step is to create a DynHost ID, which will automatically update the DNS record.
To do this, go to
Domain name, select your domain name (we will use
domain.tld for the rest of this article), then the
DynHost tab. Then select
Manage accesses and
Create a login.
We indicate the login suffix (in my case,
domain.tld-pi for a Raspberry Pi), the subdomain concerned (
* to manage all domains with this login) and a password. This account will allow us to identify ourselves to update the zone.
Once the DNS zone is propagated, your server should now be accessible from the chosen domain name.
Setting up the dynamic recording
Once the identifier has been created, we can now create the DNS record. Still in the
DynHost tab, we select
Add a DynHost, then we indicate the domain name concerned, and the current IP address. It is this last one which will be updated automatically.
Automate the DNS change
Our server must now be able to update the DNS zone when it detects an IP change. We will use
ddclient for this:
sudo apt install ddclient
Let’s skip the questions that are asked. Once finished, we directly modify the configuration file as follows (with, of course, your login, your password and your domain):
# /etc/ddclient.conf protocol=dyndns2 use=web, web=checkip.dyndns.com, web-skip='Current IP Address' server=www.ovh.com login=domaint.tld-user password='password' subdomain.domain.tld
Then, we restart the service:
sudo systemctl restart ddclient
Your server will now communicate to OVH the new IP address when it changes!