One needs to be familiar with certain shell commands to investigate system and network configurations and identify vulnerabilities in a Linux system and other processes.

Some of the useful ones are:

• whoami - to find out the current user, and who to identify logged-in users, particularly useful during reverse shell access on a host.
• uname - prints system information, which is helpful for gathering details about the machine's hardware, kernel release version and operating system.
• netstat- provides network status.

There are many more commands that can reveal a wealth of information about the user, system, and network. These commands also expose vulnerabilities that can be exploited by either an attacker or a security tester to close security gaps.