Ubuntu Server Unable to Resolve Host: Troubleshooting Guide for Devs

Hey Dev, encountering issues with resolving hostnames on your Ubuntu server can be quite frustrating. This problem can occur due to a variety of reasons, such as incorrect network configurations, DNS resolution failure, or even bad firewall settings.

In this article, we will take an in-depth look at the causes of Ubuntu server unable to resolve host and provide step-by-step instructions on how to fix this issue. So, sit tight and read on!

What is “Unable to Resolve Host” Error?

Before we dive into troubleshooting, let’s first understand what the error message “Unable to Resolve Host” means. Typically, this error message is triggered when the server fails to resolve the given hostname to an IP address.

This error can occur when you try to access a service or domain on your Ubuntu server that is not included in the local DNS resolution settings. In other words, your server does not know where to find the network resource you are trying to access.

Now that we have a basic understanding of what the error message means, let’s move on to the causes of the Ubuntu server unable to resolve host.

Causes of Ubuntu Server Unable to Resolve Host

As mentioned earlier, this error message can occur due to different reasons. Here are some of the most common causes of the Ubuntu server unable to resolve host:

1. Incorrect Network Configuration

One of the most common reasons for this error is incorrect network configurations on your Ubuntu server. If your server is not configured properly, it may not be able to communicate with other devices on the network, which can lead to hostname resolution issues.

To troubleshoot this, we recommend checking your network configurations, including network interfaces and IP settings. You can do this by running the following command on your terminal:

Command	Description
ifconfig	Show network interface details
ip addr show	Show IP address assigned to interfaces
nmcli d	Show current network device status

If the configurations are incorrect, update them and restart the network service using the command:

sudo service network-manager restart

2. DNS Resolution Failure

DNS resolution failure is another common cause of the Ubuntu server unable to resolve host. When your server is unable to resolve the hostname to an IP address using DNS, it can trigger this error message.

To fix this, we recommend checking your DNS configuration settings on your server. You can do this by checking the contents of the /etc/resolv.conf file. Ensure that the file contains the correct DNS server IP addresses for your network. You can edit the file using your preferred text editor, such as:

sudo nano /etc/resolv.conf

If the file is empty, add the following lines:

nameserver 8.8.8.8nameserver 8.8.4.4

Save and exit the file and then restart the network service by running:

sudo service network-manager restart

3. Bad Firewall Settings

If you have firewall settings configured on your server, it is possible that they are preventing your server from resolving hostnames. Firewall settings can block DNS resolution requests, which can trigger the “Unable to Resolve Host” error message.

To check if your firewall settings are causing the issue, temporarily disable the firewall and try accessing the network resources again.

You can disable the firewall using the command:

sudo ufw disable

If disabling the firewall resolves the issue, you can configure your firewall settings to allow DNS resolution requests. You can do this by adding the following rules to the firewall:

sudo ufw allow out 53sudo ufw allow in 53

Restart the firewall service using the command:

sudo ufw enable

FAQ

What is DNS?

DNS (Domain Name System) is a system that translates domain names to IP addresses, allowing computers to identify and communicate with each other on a network. DNS resolution is necessary to access websites, services, or resources on the internet or a local network.

Why is my Ubuntu server unable to resolve host?

There are several reasons why your Ubuntu server may be unable to resolve hostnames, including incorrect network configurations, DNS resolution failure, or firewall settings blocking DNS resolution requests.

How do I check my network configuration on Ubuntu server?

You can check your network configurations on your Ubuntu server by running the ifconfig, ip addr show, or nmcli d command on your terminal.

How do I check my DNS configuration on Ubuntu server?

To check your DNS configuration settings on your Ubuntu server, you can check the contents of the /etc/resolv.conf file using a text editor such as nano.

How do I disable the firewall on Ubuntu server?

You can disable the firewall on your Ubuntu server using the sudo ufw disable command on your terminal.

How do I restart the network service on Ubuntu server?

You can restart the network service on your Ubuntu server by running the sudo service network-manager restart command on your terminal.

How do I restart the firewall service on Ubuntu server?

You can restart the firewall service on your Ubuntu server by running the sudo ufw enable command on your terminal.

Conclusion

We hope this troubleshooting guide has helped you resolve the “Ubuntu server unable to resolve host” issue. By following the steps outlined in this article, you should be able to fix the issue and get back to accessing your network resources without any problems.

If you are still encountering issues after trying these steps, we recommend consulting with a professional IT support specialist for additional assistance.