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Connection error to external sites from a Docker container on Windows Server

I cannot connect to internet sites from a Docker container on Windows Server. The container runs a command to download and execute a script, but it fails due to a DNS error.

Example Dockerfile:

		

			
		

		FROM windows/servercore


SHELL ["Powershell"]


ENV UseCompression false;
RUN iex ((new-object net.webclient).DownloadString('https://example.com/install.ps1'));

When running this, I get the following error:

		

			
		

		Exception calling "DownloadString" with "1" argument(s): "The remote name could not be resolved: 'example.com'"

The container cannot access external DNS servers.
How can I fix this?

Jan Weber

7 months ago

3 answers

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03
Answer

Answers

Anna Schmidt

6 months ago

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00

Alternatively, try resetting the network settings by switching the container's network adapter from NAT to bridge mode and back. This can sometimes resolve connectivity issues.

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José Sousa

7 months ago

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00

You can add DNS servers directly in the daemon.json file, for example:

		

			
		

		{
    "dns": ["192.0.2.2", "8.8.8.8"]
}

Check the DNS on the host by running:

		

			
		

		ipconfig /all

After saving changes in daemon.json, restart Docker and test access to external sites.

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Daniel Karlsson

7 months ago

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00

The issue might be that the Docker container is using the DNS server configured for the NAT network interface. Try adding the --dns parameter with the DNS server's IP to specify which DNS to use for Docker.

Example:

		

			
		

		docker run --dns 8.8.8.8 -it windows/servercore

Or add a DNS entry in the daemon.json file:

		

			
		

		{
    "dns": ["8.8.8.8"]
}

Restart Docker to apply the changes.

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