As a penetration tester, it is important to have a good knowledge of Linux commands as you will often be working within a Linux environment.
Here are the 20 essential commands that you need to know, according to Digitalwarfare.net:
Uname -a: This command provides information about the kernel version, machine architecture and operating system; it is useful for understanding the system you are working with.
Ip a or ifconfig: These commands display network interface configurations, including IP addresses and interfaces which is useful for understanding the network configuration.
Netstat -tulnp or ss -tulnp: These commands display open ports and listening services which can inform a pen tester about services that might be vulnerable to attack.
Ps aux and Top: These commands show what is running on the system which can help to identify suspicious activity.
Whoami and id: These commands display the current user and permissions which is essential for understanding your privileges.
Sudo -l: This command displays the commands that can be executed with sudo without a password, which can be useful for privilege escalation.