Nmap, short for Network Mapper, is an open-source and highly versatile tool used by Linux system and network administrators.| 24 Nmap Commands Every Linux Admin Should Use for Network Security
Systemd is a service manager for Linux; a drop-in replacement for the init process, and the systemctl command is the primary tool to manage systemd.| How to Find Running Services in Linux with Systemd Commands [Quick Guide]
netstat (network statistics) is a command-line tool for monitoring network connections both incoming and outgoing as well as viewing routing tables, interface statistics, etc.| 20 Netstat Commands for Linux Network Management