nslookup is a powerful command-line tool used for querying the Domain Name System (DNS) to obtain domain name or IP address mapping. This tool is crucial for network administrators and systems engineers for diagnosing DNS-related issues, such as verifying DNS records, checking the status of a DNS server, or troubleshooting connectivity problems. While nslookup is often associated with Windows, it is also available and widely used in Linux environments.

In Linux, nslookup is part of the bind-utils package, which includes other DNS-related tools like dig and host. This article will guide you through the installation and usage of nslookup on a Linux system, providing practical examples to help you understand its functionality.

Examples:

1. Installing nslookup:
To use nslookup on a Linux system, you need to install the bind-utils package. This can be done using the package manager for your Linux distribution.

For Debian-based systems (e.g., Ubuntu):

   sudo apt-get update

   sudo apt-get install dnsutils

For Red Hat-based systems (e.g., CentOS, Fedora):

   sudo yum install bind-utils

2. Basic nslookup Command:
The basic usage of nslookup involves querying a domain name to obtain its IP address.

   nslookup example.com

This command will return the IP address associated with example.com.

3. Querying Specific DNS Records:
You can specify the type of DNS record you want to query. For example, to query MX (Mail Exchange) records:

   nslookup -query=mx example.com

4. Using a Specific DNS Server:
By default, nslookup uses the system's configured DNS server. You can specify a different DNS server to use for the query.

   nslookup example.com 8.8.8.8

This command queries example.com using Google's public DNS server (8.8.8.8).

5. Reverse DNS Lookup:
You can perform a reverse DNS lookup to find the domain name associated with an IP address.

   nslookup 93.184.216.34

This command will return the domain name associated with the IP address 93.184.216.34.

6. Interactive Mode:
nslookup also has an interactive mode that allows you to perform multiple queries in a single session.

   nslookup

Once in interactive mode, you can type domain names or IP addresses to query them.

7. Exiting Interactive Mode:
To exit interactive mode, simply type:

   exit