Linux commands for system administrators

1. What Is nslookup?

nslookup queries DNS servers for domain name resolution and is useful for inspecting basic DNS behavior. Though older and less flexible than dig, it’s still available on many systems and familiar to network admins.

2. Installing nslookup

It’s part of the dnsutils or bind-utils packages:

sudo apt install dnsutils

sudo yum install bind-utils

3. Basic Usage

nslookup example.com

Returns the IP address and DNS server information.

4. Useful nslookup Queries

• Query using a specific DNS server:

nslookup example.com 8.8.8.8

• Query MX records:

nslookup -query=MX example.com

• Query NS records:

nslookup -type=NS example.com

5. What Is host?

host is a compact DNS lookup tool that gives concise output for common record types. It’s simpler than nslookup and well-suited for scripting and automation.

6. Installing host

Also included in dnsutils:

sudo apt install dnsutils

7. Basic Usage of host

host example.com

Displays IPv4 or IPv6 addresses directly.

8. Common host Options

• Query specific record type:

host -t MX example.com

host -t NS example.com

host -t TXT example.com

• Use specific DNS server:

host example.com 8.8.8.8

• Reverse lookup:

host 8.8.8.8

9. Comparison Table

Feature	nslookup	host
Output format	Verbose	Concise
Supports multiple record types	✅	✅
Script-friendly	❌	✅
Specify DNS server	✅	✅

10. Practical Use Cases

• Check if a domain resolves correctly
• Validate email-related DNS records (MX, SPF)
• Debug DNS server response behavior
• Incorporate checks into automation scripts

11. Conclusion

nslookup and host offer simple, fast methods for DNS diagnostics in Linux. While dig provides more detail and flexibility, these two tools are valuable for quick checks, scripting, and basic troubleshooting.