How to Look Up DNS Entries Using dig on the Terminal in Ubuntu

This is an article about how to use the dig command, a powerful utility for querying the Domain Name System (DNS) from the terminal in Ubuntu. In this article you will find information about what the dig tool is and why it’s essential for network administrators and developers who work with DNS records.

Introduction

Understanding and managing DNS entries can be crucial when configuring domain names, setting up websites, or troubleshooting connectivity issues on your local network or across the internet. The dig command, which stands for “Domain Information Groper,” is a powerful tool that allows you to perform various types of DNS queries. This article will guide you through using dig in Ubuntu, offering insights into its features and providing practical examples.

What is DNS?

Before diving into how to use dig, it’s important to understand what DNS (Domain Name System) is. DNS translates human-readable domain names like “www.example.com” into IP addresses that computers can interpret and connect to. It acts as a distributed database where records are stored, and every domain has an associated set of such records.

What is dig?

The dig utility in Ubuntu is a flexible command-line tool for querying DNS servers directly. Unlike using a web interface or other tools with limited features, dig offers comprehensive control over the types of queries you can make and the information returned by DNS servers. This makes it invaluable for network administrators who need to diagnose issues, test configurations, or understand how their domain names are resolving.

Installing dig

To use dig, you first need to ensure that it’s installed on your Ubuntu system. The dig command is part of the dnsutils package which can be easily installed using apt-get:

Once installed, you should have access to the dig utility.

Basic Usage

The simplest way to use dig is with just a domain name. For example:

This command queries DNS records for “example.com” and returns all available information in a standard format:

• Query: The query type, often “IN” (Internet) by default.
• NAME: The domain name you queried.
• CLASS: Usually “IN.”
• TYPE: Type of record returned. Common types include A, AAAA, MX, TXT, etc.
• TTL: Time to live in seconds before the data expires and must be refreshed.

For a more detailed output, you can specify different query types:

Advanced Queries

Specifying Nameservers

By default, dig uses your system’s DNS settings to determine which nameserver to use. However, you might want to test specific servers directly.

To do this:

Filtering Output with +short

If you just need a quick lookup without the full verbose output, +short can be used:

This is particularly useful for scripting or quickly checking if a domain resolves to an expected address.

Querying Specific Types of Records

You’re not limited to just MX and A types. You can query any type supported by DNS:

Troubleshooting with dig

If you suspect issues with your DNS configuration or if a domain isn’t resolving properly, dig offers several ways to diagnose problems.

Checking TTLs

A high or low TTL can affect how changes propagate across the internet:

Analyzing DNS Propagation

After making a change, use dig to monitor when it propagates globally. This is especially useful with services like Cloudflare or other CDN providers.

This command will continuously ping the domain and output any changes in IP addresses, helping you track when DNS records update across different servers worldwide.

Conclusion

This article provided an overview of how to use dig for looking up DNS entries on Ubuntu. Whether you’re setting up a new website, diagnosing issues with your current configuration, or simply learning more about DNS management, the dig utility offers unparalleled flexibility and control over querying DNS records.

By mastering commands like those covered in this article, network administrators can gain deeper insights into their systems’ performance and ensure smooth operation of services that rely heavily on DNS.