Error: Internet Connection Loss due to DNS Failure in Docker (Umbrel OS)

✨ Quick Answer

A very common critical failure in home servers based on the Umbrel OS ecosystem occurs when Docker containers (such as Sonarr or your nodes) suddenly stop downloading updates or lose connection to external servers, throwing Temporary failure in name resolution errors. This happens because the Docker daemon loses the route to the local DNS resolver of the host operating system.

Quick Diagnostics

Cause

Internal Docker DNS resolver failing on Umbrel OS

Solution

Set public DNS in /etc/docker/daemon.json (e.g. "dns": ["1.1.1.1"])

Cause

Port 53 conflict with systemd-resolved service

Solution

Set DNSStubListener=no in /etc/systemd/resolved.conf

A very common critical failure in home servers based on the Umbrel OS ecosystem occurs when Docker containers (such as Sonarr or your nodes) suddenly stop downloading updates or lose connection to external servers, throwing Temporary failure in name resolution errors. This happens because the Docker daemon loses the route to the local DNS resolver of the host operating system.

Step-by-Step Solution

1. 1

   Step 1: Verify the internal network block

   Access your Umbrel server via SSH and enter the affected container to check if it responds to a direct numerical ping but fails to resolve text names:

   BASH Copy

   # Test direct Google IP (If it responds, there is internet but no DNS)
   docker exec -it nombre_contenedor ping -c 3 8.8.8.8
   

2. 2

   Step 2: Force global public DNS in the Docker configuration

   To bypass Umbrel's routing blocks, we can define static and immutable DNS servers for the entire Docker engine. Edit the global configuration file:

   BASH Copy

   sudo nano /etc/docker/daemon.json
   

   Add or merge the following lines with the stable DNS of Cloudflare and Google inside the JSON object:

   JSON Copy

   {
     "dns": ["1.1.1.1", "8.8.8.8"]
   }
   

   Save the file (Ctrl + O, Enter) and close the editor (Ctrl + X).

3. 3

   Step 3: Restart the Docker service

   Apply a forced restart to the system service so it brings up all network interfaces with the new injected DNS:

   BASH Copy

   sudo systemctl restart docker