Linux commands for system administrators

dig Command

| dig |

| domain analysis |

| nameservers |

1. What Is dig?

dig is a command-line utility used to send DNS queries to nameservers and display structured responses. It’s often preferred over nslookup for its flexibility and detailed output.

2. Installing dig on Linux

Included in packages like dnsutils or bind-utils:

sudo apt install dnsutils        # Debian / Ubuntu

sudo yum install bind-utils      # CentOS / RHEL

3. Basic Usage

Query a domain:

dig example.com

Output includes sections: HEADER, QUESTION, ANSWER, AUTHORITY, and ADDITIONAL.

4. Common Record Types

A record: IPv4 address

dig example.com A

AAAA: IPv6 address

dig example.com AAAA

MX: Mail exchange servers

dig example.com MX

NS: Nameservers

dig example.com NS

TXT: Text records (e.g., SPF)

dig example.com TXT

5. Useful Switches and Flags

Option	Purpose	Example
+short	Display compact output	`dig example.com +short`
+noall +answer	Show only answer section	`dig example.com +noall +answer`
@server	Specify DNS server	`dig example.com @8.8.8.8`
-x	Reverse lookup for IP	`dig -x 93.184.216.34`
+trace	Trace from root servers	`dig example.com +trace`

6. Checking SOA and TTL

View Start of Authority and TTL values:

dig example.com SOA

dig example.com +noall +answer +ttl

7. Reverse DNS Lookup

Find hostname associated with an IP:

dig -x 8.8.8.8

8. Practical Use Cases

Verify DNS settings for domains
Troubleshoot name resolution failures
Validate SPF/DKIM TXT records
Trace DNS resolution hierarchy

9. Conclusion

dig is an essential utility for domain analysis and DNS diagnostics in Linux. With support for granular queries, server specification, and filtered output, it empowers admins, developers, and analysts to audit DNS behavior efficiently.