Troubleshooting: Debian Server Not Resolving DNS


Welcome to our troubleshooting guide on Debian Server Not Resolving DNS. Before delving into the details, let’s start with the basics. The Domain Name System (DNS) is a naming system for computers, servers, or any device connected to the internet. DNS translates domain names into IP addresses to enable devices to access websites and other online resources. When a server is unable to resolve DNS, it can cause significant inconvenience and even affect business operations. Our guide aims to help you resolve this issue quickly and efficiently.

What is Debian Server?

Debian is a free and open-source operating system that provides stability, reliability and security. It is widely used as a server operating system due to its extensive package management system and powerful set of tools. Debian OS-based servers are particularly popular in web development environments, including cloud computing, due to its ability to host advanced web applications and sites.

Reasons Why DNS Might Not Be Resolving

There are several reasons why a Debian Server might not resolve DNS. It could be a network error, a software configuration issue, or a hardware fault. Below are the most common reasons that Debian Server users encounter.

Incorrect DNS Server Address

One of the primary reasons why DNS is not resolving is because the server might be incorrectly configured to use the wrong DNS server address. There are two types of DNS servers; internal and external. Internal DNS servers are set up by companies to host their DNS records internally, while external DNS servers are used to host DNS records for domains that are publicly available.

If your server is configured to use an incorrect DNS server address, it won’t be able to resolve DNS requests correctly. This might lead to timeouts and other DNS errors.

DNS Cache Issues

DNS caches are used to store DNS resolution records to make future responses faster. However, if your server’s DNS cache is corrupted or malfunctioning, it might not be able to resolve DNS requests correctly.

This can happen if the DNS entries become invalid or if there is an issue with the expiry of the DNS records. In such cases, clearing the DNS cache might resolve the issue.

Network Connectivity Issues

Debian servers require network connectivity to access the Internet, and if it is lost, it can cause DNS resolution issues. This could happen due to several issues, such as network configuration, faulty cables, or hardware issues.

If your server is unable to connect to the internet or a network, DNS resolution could be affected as well.

Firewall Configuration

Firewalls are essential for server security, but they could also cause DNS resolution issues. Firewall settings can block DNS requests or interfere with the DNS resolution process, leading to errors.

In such cases, configuring the firewall to allow DNS requests or disabling it temporarily might solve the problem.

Software Configuration Issues

Sometimes software configuration issues lead to Debian Server not resolving DNS. These could be due to factors such as the wrong configuration of network interfaces, network configuration files, or DNS settings.

Software configuration issues are often resolved by reconfiguring the settings.

Hardware Issues

Hardware is always a potential cause of server issues, including DNS resolution. Defective hardware components, such as network interface cards, or cabling issues could affect network connectivity and cause DNS resolution problems.

Advantages and Disadvantages of Debian Server


Free and Open Source
Debian is free and open-source, which makes it an affordable option.
Debian’s stability in varying network environments makes it a favorite for critical systems.
Package Management
Debian provides an extensive package management system that makes it easier to install and maintain software.
Debian’s security features are regularly updated and maintained by a global community of developers.
Wide Community Support
Debian has a vast developer community that provides support and regular updates.
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Debian Server has a limited user interface, and managing it typically requires an experienced administrator. It also lacks graphical tools and requires users to have familiarity with command-line interfaces.

Frequently Asked Questions

How do I check if DNS is `up and running`?

Run the `dig` command followed by the DNS server IP address to confirm if it is up and running.

Can network connectivity issues cause Debian Server not resolving DNS?

Yes, network connectivity issues such as misconfigured cables, hardware issues, or network configuration, could cause DNS resolution issues on Debian servers.

What should I do if DNS cache is corrupted?

Clear the DNS cache by running the `systemd-resolve –flush-caches` command.

How do I know if I am using the wrong DNS server address?

Check `/etc/resolv.conf` to confirm if the correct DNS server address is set.

How do I reconfigure network interfaces?

Reconfigure network interfaces by editing the `/etc/network/interfaces` file.

How can I configure firewalls to allow DNS requests?

Edit firewall rules to allow DNS requests through port 53.

Can software configuration issues cause Debian Server not resolving DNS?

Yes, software configuration issues, including network interfaces and configuration files, could cause DNS resolution issues on Debian servers.

What hardware issues could affect DNS resolution on Debian servers?

Defective hardware components, such as network interface cards, cables, and switches, could cause DNS resolution issues on Debian servers.

How can I disable a firewall temporarily?

Run the `systemctl stop ` command to stop the firewall temporarily.

How do I update Debian Server?

Run `apt-get update && apt-get upgrade` to update Debian server.

Does Debian Server support multiple users?

Yes, Debian Server supports multiple users, and system administrators can configure user groups and set individual user permissions.

Can I install a web server on Debian Server?

Yes, Debian Server supports web servers like Apache and NGINX.

What is DNS resolution?

DNS resolution is the process of converting domain names into IP addresses to enable device connectivity on the internet.

How long does it take to resolve DNS requests on Debian Server?

DNS resolution speed depends on server configuration, network connectivity, and the efficiency of the DNS server.


In conclusion, DNS resolution issues on Debian Server could be caused by several factors, including incorrect DNS server address, DNS cache issues, network connectivity, firewall settings, software configuration issues, and hardware issues.

Resolving these issues could require different techniques, such as reconfiguring network interfaces, clearing cache, changing DNS server settings, or hardware replacement.

Take Action

If you’re facing DNS resolution issues on Debian Server, take prompt action by following the tips and techniques outlined in our guide. Don’t let DNS issues affect your business operations and productivity.

Closing or Disclaimer

The information provided in this guide is for informational purposes only. We are not responsible for any damages or losses that may arise from the use of the information presented herein. We recommend that you seek professional assistance when dealing with server issues.

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