Resolving “Ubuntu Server Could Not Resolve Host” Error

Hello Dev, welcome to this comprehensive guide on resolving “Ubuntu server could not resolve host” error. This error occurs when your Ubuntu server cannot establish a connection with a hostname or domain name. It can occur due to various reasons, including DNS resolution errors, network issues, firewall restrictions, or misconfiguration in the hostname settings.

Understanding the “Could Not Resolve Host” Error

Before we delve into the solutions, it’s essential to understand the error message and its implications. The error message reads like this:

Could not resolve hostname (hostname): Name or service not known

This means that your Ubuntu server cannot resolve a hostname to its corresponding IP address. As a result, it cannot establish a connection with the hostname/domain name specified in the command, configuration file, or any other network-related tasks.

Possible Causes of the “Could Not Resolve Host” Error

Several factors can cause the “could not resolve host” error message. Some of the common causes include:

Solutions to “Ubuntu Server Could Not Resolve Host” Error

Check DNS Resolution

The first step to solve “ubuntu server could not resolve host” error is to check the DNS resolution. Follow these steps:

Step 1: Check DNS Server Status

First, you need to ensure that the DNS server is working correctly. Execute the following command to check the DNS server status:

systemctl status systemd-resolved

If the DNS server is inactive, start it by executing the command:

sudo systemctl start systemd-resolved

If the server is already running, restart it by executing:

sudo systemctl restart systemd-resolved

Step 2: Flush DNS Cache

If the DNS server is running, flush the DNS cache by executing:

sudo systemd-resolve –flush-caches

Step 3: Check DNS Configuration

If the DNS server is active, and you have flushed the cache, verify the DNS configuration by executing:

cat /etc/resolv.conf

The file should contain the correct DNS server IP address(es). If it’s not correct, you can edit the file using nano or vi editor:

sudo nano /etc/resolv.conf

Change the IP address to the correct one, save and exit.

Check Network Connectivity

The second step is to check the network connectivity of your Ubuntu server. Follow these steps:

Step 1: Check Network Configuration

Verify the network configuration by executing the command:

ip addr show

The output should display the network interface and IP address assigned. If it’s not correct, edit the configuration file by executing:

sudo nano /etc/network/interfaces

Replace the incorrect configuration with the correct one, save and exit.

Step 2: Check Firewall Restrictions

Firewall restrictions can block network traffic and prevent the server from resolving the hostname. Ensure that the firewall is not blocking the traffic by executing:

sudo ufw status

If the firewall is active and blocking the traffic, add a rule to allow traffic for that particular hostname by executing:

sudo ufw allow out to (hostname)

Replace (hostname) with the domain name or hostname causing the error.

Check Hosts File Configuration

The third step is to check the hosts file configuration. Follow these steps:

Step 1: Check Hosts File Entries

Verify the hosts file entries by executing the command:

cat /etc/hosts

The output should contain the correct IP address and hostname mapping. If it’s not correct, edit the file by executing:

sudo nano /etc/hosts

Replace the incorrect mapping with the correct one, save and exit.

Step 2: Reboot The System

After making the changes in the DNS resolution, network connectivity, and hosts file configuration, reboot the system and verify if the error is resolved.

Frequently Asked Questions (FAQ)

1. Why am I getting the “Could Not Resolve Host” error message?

You are getting the error message because your Ubuntu server is unable to resolve the hostname to its corresponding IP address.

2. What are the possible causes of the error message?

The possible causes of the error message include DNS resolution errors, network issues, firewall restrictions, or misconfiguration in the hostname settings.

3. How can I solve the “Could Not Resolve Host” error message?

You can solve the “could not resolve host” error message by checking the DNS resolution, network connectivity, and hosts file configuration. Edit the configuration files as necessary and reboot the system.

4. What should I do if the error message persists?

If the error message persists, contact your system administrator or internet service provider for further assistance.

5. Can the error message occur in other operating systems?

Yes, the error message can occur in other operating systems such as Windows and macOS.

That brings us to the end of our guide on resolving “ubuntu server could not resolve host” error. We hope this article was helpful in resolving your query. Thank you for reading.