How to use the command adig (with examples)

The adig command is used to print information received from Domain Name System (DNS) servers. It allows users to retrieve DNS records for a specific hostname and also provides options for extra debugging output, connecting to a specific DNS server, and using specific TCP or UDP ports for the connection.

Use case 1: Display A record from DNS for hostname(s)

Code:

adig example.com

Motivation:

This use case is useful when you want to retrieve the A record for a specific hostname. The A record maps a hostname to its corresponding IP address. By executing this command, you can easily obtain the IP address associated with the given hostname.

Explanation:

• example.com: This argument specifies the hostname for which you want to retrieve the A record.

Example output:

# adig example.com

1.2.3.4

In this example, the A record for example.com is 1.2.3.4.

Use case 2: Display extra debugging output

Code:

adig -d example.com

Motivation:

When troubleshooting DNS-related issues, it can be helpful to enable extra debugging output. By using the -d option, you can obtain more detailed information about the DNS request and response, which can aid in diagnosing and resolving any problems.

Explanation:

• -d: This option enables extra debugging output.

Example output:

# adig -d example.com

Debug information:
- Request sent to DNS server: 1.2.3.4
- Response received from DNS server: 1.2.3.4

Details:
- Request: A record for example.com
- Response: A record found, IP address: 1.2.3.4

In this example, the command provides additional debugging information, including details about the DNS request and response.

Use case 3: Connect to a specific DNS server

Code:

adig -s 1.2.3.4 example.com

Motivation:

In some scenarios, you may need to connect to a specific DNS server to retrieve DNS records. By using the -s option, you can specify the DNS server’s IP address and ensure that the command fetches the desired records from the intended server.

Explanation:

• -s 1.2.3.4: This option specifies the IP address of the DNS server to connect to.

Example output:

# adig -s 1.2.3.4 example.com

1.2.3.4

In this example, the command connects to the DNS server at 1.2.3.4 and retrieves the A record for example.com.

Use case 4: Use a specific TCP port to connect to a DNS server

Code:

adig -T port example.com

Motivation:

By default, DNS queries are sent over UDP (User Datagram Protocol). However, in some cases, you may want to use TCP (Transmission Control Protocol) instead. This can be necessary when UDP is blocked or unreliable. With the -T option, you can specify a specific TCP port to connect to the DNS server.

Explanation:

• -T port: This option specifies the TCP port to use for the connection.

Example output:

# adig -T 5353 example.com

1.2.3.4

In this example, the command connects to the DNS server using TCP port 5353 and retrieves the A record for example.com.

Use case 5: Use a specific UDP port to connect to a DNS server

Code:

adig -U port example.com

Motivation:

Although DNS queries are typically sent over UDP, there may be situations where you want to use a specific UDP port for the connection. This can be useful when you need to work with a specific network configuration or if you want to test how a DNS server handles queries on a specific port. With the -U option, you can specify the UDP port to utilize.

Explanation:

• -U port: This option specifies the UDP port to use for the connection.

Example output:

# adig -U 53 example.com

1.2.3.4

In this example, the command connects to the DNS server using UDP port 53 and retrieves the A record for example.com.

Conclusion

The adig command is a versatile tool for obtaining DNS information. Whether you need to retrieve DNS records, enable debugging output, connect to a specific DNS server, or use specific TCP or UDP ports, the adig command provides the flexibility and capability to fulfill your DNS-related needs.