How to Use Wget to Download and Log DNS Lookups on Ubuntu

This guide explains how to utilize the wget command-line utility on Ubuntu to download files while simultaneously recording DNS resolution details. By combining specific wget flags, you can capture network debugging information, including hostname lookups, into a local log file for analysis.

To begin, ensure wget is installed on your Ubuntu system. While it is pre-installed on most versions, you can verify or install it by running sudo apt update && sudo apt install wget in your terminal. Once ready, you can proceed to download a file and log the DNS resolution process using the debug and output logging flags.

The primary command to achieve this combines the -d flag for debug output and the -o flag to specify the log file. Execute the following command in your terminal, replacing the URL with your target file and log.txt with your preferred log filename:

wget -d -o log.txt https://example.com/file.zip

In this command, the -d option enables debug mode, which forces wget to print detailed information about its operations, including the DNS resolution step where it resolves the domain name to an IP address. The -o option redirects all standard output and error messages, including the debug information, into the specified log file instead of displaying it only on the screen.

After the download completes, you can inspect the log file to verify the DNS lookup details. Use the cat command to view the contents of the log:

cat log.txt

Search through the output for lines starting with Resolving. This line indicates the DNS lookup event, showing the domain name queried and the IP address returned. This method provides a straightforward way to audit network resolution activity specific to the wget process without requiring additional network monitoring tools.