Resolving Unable to retrieve templates via the network Error in Portainer on Raspberry Pi

Описание: Learn how to fix the Portainer templates loading error caused by unbound in your Raspberry Pi setup with Pi-hole.
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This video is based on the question https://stackoverflow.com/q/73567647/ asked by the user 'Madriesen' ( https://stackoverflow.com/u/11598824/ ) and on the answer https://stackoverflow.com/a/77975086/ provided by the user 'JaysonP' ( https://stackoverflow.com/u/23377054/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Fixing Portainer Template Fetch Errors on Raspberry Pi

If you’re managing your Docker containers on a Raspberry Pi using Portainer and you've got Pi-hole and Unbound set up, you might have encountered the frustrating 500: Unable to retrieve templates via the network error when trying to fetch portainer templates. This issue often arises due to DNS resolution problems with your Unbound configuration. Let’s break down the causes and explore how you can resolve it.

Understanding the Problem

When you attempt to fetch templates from Portainer, it requires access to external resources, which might involve looking up URLs like http://raw.githubusercontent.com. In your case, the error indicates that DNS queries are not resolving properly:

[[See Video to Reveal this Text or Code Snippet]]

This error shows that your Docker container is trying to resolve the domain through Unbound's DNS service (which appears to be misconfigured or not reachable), resulting in the inability to retrieve any templates.

Why This Happens

Misconfigured DNS: If your router’s DNS settings are pointing solely to Unbound with no fallback, and there's an issue with Unbound's functionality, your Docker containers won't be able to resolve domain names.

Unreachable External DNS: Portainer in a Docker environment may have difficulty reaching external DNS services due to network settings.

Steps to Resolve the Issue

To fix the DNS resolution issue for Portainer and successfully fetch templates again, follow these steps:

Step 1: Verify DNS Settings on Your Router

Access your router’s configuration page and check the DNS settings under the LAN setup.

If you previously had OpenDNS or another DNS provider set, those entries may have been removed when you configured Unbound.

Step 2: Add a Secondary DNS

Add a backup DNS entry that can act when Unbound fails. This could be any reliable DNS service such as OpenDNS (208.67.222.222) or Google DNS (8.8.8.8).

Step 3: Update Portainer Docker Run Command

When starting the Portainer container, ensure you're using the appropriate DNS settings. Run the following command, which specifies a secondary DNS entry for the Portainer container:

[[See Video to Reveal this Text or Code Snippet]]

Parameters Explained:

-d runs the container in detached mode.

-p 9000:9000 and -p 9443:9443 map the container ports to your host.

--dns=208.67.222.222 sets the DNS server for this specific container.

Conclusion

By ensuring you have a secondary DNS configured and updating the Portainer container with the correct DNS settings, you should resolve the Unable to retrieve templates via the network error you experienced on your Raspberry Pi. This will allow you to fetch and update your templates smoothly again.

Keep your systems updated, and remember to revert any changes if things don’t work as intended. If you need to troubleshoot further, monitor Unbound’s performance and DNS queries to ensure everything is functioning correctly.

Happy Dockering!