Use nslookup Command in Linux with Examples: Best For DNS-related Tasks

In this guide, we’ll explore how to Use nslookup Command in Linux. Name server lookup (nslookup) is a vital command-line tool that allows you to query Domain Name System (DNS) servers. This enables you to find the IP address associated with a domain name or retrieve various DNS records for a specific hostname. Furthermore, nslookup supports reverse DNS lookups, where you input an IP address to find the corresponding domain. The nslookup tool is particularly useful for DNS-related tasks, such as server testing and general Linux troubleshooting.

Let’s delve into how to use nslookup effectively on your Linux system.

To follow along with this guide, you’ll need access to a Linux server. Log in to your server and proceed with the following steps.

Step 1. Install nslookup in Linux

While nslookup is often pre-installed on major operating systems, you might need to install it if it’s missing. Here’s how to install it on different Linux distributions:

• On Ubuntu / Debian:

  sudo apt install dnsutils

• On CentOS, Fedora, and Red Hat:

  On these distributions, nslookup is included within the bind-utils package. Install it using:

  sudo dnf install bind-utils

Step 2. nslookup Modes with Examples

Nslookup offers two primary modes of operation: interactive and non-interactive.

Interactive Mode:

To enter nslookup interactive mode, simply type the command:

nslookup

This will present a prompt where you can issue multiple queries:

>

For instance, to find information about www.google.com, you would type:

> www.google.com

Server:         127.0.0.53
Address:        127.0.0.53#53

Non-authoritative answer:
www.google.com  canonical name = ddd.l.google.com.
Name:   ddd.l.google.com
Address: 142.250.184.78

In interactive mode, you can set options before issuing queries. The syntax for setting options is:

set [option]

For example, to retrieve the name servers for google.com, use:

> set type=ns
> google.com

Server:         127.0.0.53
Address:        127.0.0.53#53

Non-authoritative answer:
google.com      nameserver = ns1.google.com.
google.com      nameserver = ns2.google.com.
google.com      nameserver = ns3.google.com.
google.com      nameserver = ns4.google.com.

Authoritative answers can be found from:
ns1.google.com  internet address = 216.239.32.10
ns2.google.com  internet address = 216.239.34.10
ns3.google.com  internet address = 216.239.36.10
ns4.google.com  internet address = 216.239.38.10

To exit interactive mode, type:

> exit

Non-interactive Mode:

Non-interactive mode is for executing single queries directly from the command line. The syntax is:

nslookup [options] [domain-name]

For example:

nslookup www.google.com

Server:         127.0.0.53
Address:        127.0.0.53#53

Non-authoritative answer:
www.google.com  canonical name = ddd.l.google.com.
Name:   ddd.l.google.com
Address: 142.250.184.78

Step 3. nslookup Command Options

Here’s a table of common and useful nslookup command options in Linux:

nslookup Option	Description
-domain=[domain-name]	Change the default DNS name.
-debug	Show debugging information.
-port=[port-number]	Specify the port for queries. The default port number is 53.
-timeout=[seconds]	Specify the time allowed for the server to respond.
-type=a	View information about the DNS A address records.
-type=any	View all available records.
-type=hinfo	View hardware-related information about the host.
-type=mx	View Mail Exchange server information.
-type=ns	View Name Server records.
-type=ptr	View Pointer records. Used in reverse DNS lookups.
-type=soa	View Start of Authority records.

Step 4. Work with nslookup in Linux

Let’s explore some common use cases for the nslookup command in Linux:

• Finding the host IP address
• Finding the domain name of an IP address
• Finding mail servers for a domain

These are frequently encountered scenarios when working with DNS.

Find the Host IP Address

To find the IP address of a host, use the following syntax:

Non-interactive mode:

nslookup domain-name

Interactive mode:

nslookup
> domain-name

Find the Domain Name of an IP Address

To perform a reverse DNS lookup and find the domain name associated with an IP address:

Non-interactive mode:

nslookup IP-address

Interactive mode:

nslookup
> IP-address

Find Mail Servers for a Domain

To discover the mail servers responsible for handling email for a specific domain:

Non-interactive mode:

nslookup -querytype=mx domain-name

Interactive mode:

nslookup
> set type=mx
> domain-name

These commands provide essential DNS information for various tasks.

Conclusion

You’ve now learned how to Use nslookup Command in Linux with Examples. The primary application of nslookup lies in diagnosing and resolving DNS-related problems. Mastering nslookup is a valuable skill for any Linux system administrator or developer.

Alternative Solutions for DNS Lookups

While nslookup is a traditional and widely available tool, alternative solutions offer more features, cleaner output, and improved functionality. Here are two alternatives to consider:

1. dig (Domain Information Groper)

dig is a more advanced and feature-rich command-line tool for querying DNS name servers. It provides more detailed information and greater control over the query process compared to nslookup. It’s often preferred for its clarity and comprehensive output.

Installation:

dig is typically part of the bind-utils or dnsutils package, similar to nslookup. If you don’t have it, install it using:

• Ubuntu/Debian:

  sudo apt install dnsutils

• CentOS/Fedora/Red Hat:

  sudo dnf install bind-utils

Examples:

• Finding the A record (IP address) for a domain:

  dig www.google.com A

  This command specifically requests the A record for www.google.com, providing the IP address(es).

• Finding the MX records (mail servers) for a domain:

  dig google.com MX

  This retrieves the MX records, showing the mail servers and their priority for the domain.

• Performing a reverse DNS lookup:

  dig -x 8.8.8.8

  This command performs a reverse lookup on the IP address 8.8.8.8 (Google’s public DNS server), revealing the corresponding domain name.

Advantages of dig over nslookup:

• More detailed output: dig provides more comprehensive information, including the DNS server used, query time, and response flags.
• Greater control: dig offers more options for customizing queries, such as specifying the DNS server to use, setting the timeout, and requesting specific record types.
• Scripting-friendly output: The output of dig is generally easier to parse in scripts than nslookup’s output.

2. host Command

The host command is another simple and straightforward tool for performing DNS lookups. It’s often used for basic queries and provides a cleaner output than nslookup for common tasks.

Installation:

Like dig, host is usually part of the bind-utils or dnsutils package. Install it if needed using the same commands as for dig.

Examples:

• Finding the IP address for a domain:

  host www.google.com

  This command returns the IP address(es) associated with www.google.com.

• Finding the MX records for a domain:

  host -t mx google.com

  This retrieves the MX records for google.com, similar to the dig command.

• Performing a reverse DNS lookup:

  host 8.8.8.8

  This performs a reverse lookup on the IP address 8.8.8.8.

Advantages of host over nslookup:

• Simpler syntax: The host command has a more concise syntax, making it easier to use for basic lookups.
• Cleaner output: The output of host is generally cleaner and more human-readable than nslookup’s output.
• Widely available: Like nslookup, host is typically pre-installed on many Linux systems.

Choosing the Right Tool:

• For simple DNS lookups and quick checks, host provides a clean and easy-to-use interface.
• For more detailed analysis, troubleshooting, and scripting, dig is the preferred choice due to its comprehensive output and advanced features.
• While nslookup is still a viable option, dig and host offer significant improvements in terms of functionality and usability.

In conclusion, while Use nslookup Command in Linux can be a useful tool, dig and host offer superior alternatives for DNS lookups in Linux environments. Consider adopting these tools for improved clarity, control, and efficiency in your DNS-related tasks.