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Asked: 2024-09-25T16:53:39+05:30 In:

How can I configure my Ubuntu 22.04 server to rely exclusively on the DNS servers specified in the /etc/resolv.conf file?

I’ve been digging into configuring my Ubuntu 22.04 server lately, and I hit a bit of a roadblock that I hope someone here can help me with. So, here’s the thing: I want my server to rely exclusively on the DNS servers I’ve put in the /etc/resolv.conf file. However, I’m a bit unsure about how to ensure that it doesn’t fall back on the default DNS settings or any other DNS caching mechanisms that might be lurking around.

My setup involves a few critical applications that absolutely need to use the specified DNS servers for name resolution to function correctly. I’m particularly concerned about things like systemd-resolved, which I’ve read can sometimes interfere with custom configurations by sending requests to its own set of DNS servers, rather than the ones I’ve specified. I want to make sure that when my applications try to resolve DNS queries, they only use what I listed in /etc/resolv.conf.

I’ve done some searches, and some articles suggest disabling systemd-resolved altogether, while others recommend just configuring it to pass queries directly to the servers in resolv.conf. I’m not exactly sure which route would be the best. Ideally, I’d like a straightforward approach without diving too deep into convoluted configurations.

Also, if I do disable systemd-resolved, will that have any unexpected effects down the line? I mean, are there any networking features or services that might depend on it? I’m looking for a configuration that’s both simple and effective, and I’m all ears for detailed steps or any potential pitfalls to watch for.

If anyone has gone through this process or has pointers on how to achieve a solid DNS setup without having to deal with conflicting settings, I’d really appreciate hearing your experiences or advice! Thanks in advance!

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    2 Answers






    1. Ubuntu DNS Configuration Help

      DNS Configuration on Ubuntu 22.04

      So, if you want your Ubuntu server to use only the DNS servers you put in /etc/resolv.conf, you might want to disable systemd-resolved altogether. Here’s a simple way to do it:

      1. First, stop and disable the systemd-resolved service:

        sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved
      2. Next, make sure the /etc/resolv.conf file is using your preferred DNS servers. You might need to manually create it as a symlink if it’s been set up by systemd:

        sudo rm /etc/resolv.conf
echo "nameserver 8.8.8.8" | sudo tee /etc/resolv.conf
echo "nameserver 8.8.4.4" | sudo tee -a /etc/resolv.conf

        Replace the IP addresses above with your own DNS servers.

      Now, about your concern on unexpected effects: some features might depend on systemd-resolved, but disabling it is generally fine, especially if you don’t need features like DNSSEC or LLMNR. Just keep in mind that if you’re using any network management tools (like NetworkManager), you may need to adjust their settings accordingly.

      If you run into any issues with your applications, make sure they’re not set to use a different mechanism for DNS lookups. Other than that, it should be pretty straightforward!

      Good luck, and don’t hesitate to ask if you have more questions!


    2. To ensure your Ubuntu 22.04 server exclusively uses the DNS servers specified in /etc/resolv.conf without falling back on systemd-resolved or any other default configurations, it’s best to disable systemd-resolved entirely. You can do this with the following commands: first, stop the service using sudo systemctl stop systemd-resolved, and then disable it with sudo systemctl disable systemd-resolved. After stopping the service, you should also remove the symbolic link for resolv.conf by executing sudo rm /etc/resolv.conf and create a new resolv.conf file with your desired DNS servers manually. You can create the file with sudo nano /etc/resolv.conf and add entries like nameserver 1.1.1.1 and nameserver 8.8.8.8 (or any other DNS servers you prefer).

      Disabling systemd-resolved is generally safe for most server configurations, especially if your applications are explicitly designed to rely on the DNS servers listed in resolv.conf. However, be aware that some network management features or services may depend on systemd-resolved, and disabling it could potentially affect them. To avoid unforeseen issues, ensure that your network configuration files (like NetworkManager or netplan, depending on how your network is set up) do not rely on resolved DNS settings. Monitor your applications and services closely after making these changes to confirm that there are no regressions related to DNS resolution. Stick to this straightforward approach, and you’ll have a robust DNS configuration tailored to your specific needs.

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