TestOut Linux Pro Practice Test 2026 - Free Linux Pro Practice Questions and Study Guide

The command used to list all installed packages in a Debian-based system is "dpkg -l". This command interfaces directly with the Debian package management system, specifically the dpkg tool, which handles the installation, removal, and management of Debian packages.

When you run "dpkg -l", it provides a comprehensive list of all packages currently installed on the system, showing details such as the package name, version, architecture, and a brief description. This output is particularly useful for administrators and users who need to verify which software is installed or troubleshoot package-related issues.

While "apt list" is also a valid command for this purpose, it is not as direct as "dpkg -l", since "apt list" can also show packages that are available for installation or upgrade, not just those that are currently installed. The other options, such as "yum list installed" and "pkg-info", pertain to package managers and systems unrelated to Debian-based distributions, specifically Red Hat-based systems and package formats other than .deb, respectively. Therefore, "dpkg -l" is the command that accurately fulfills the requirement for listing installed packages in a Debian-based environment.