Useful built-in commands for Linux reconnaissance

• cat /etc/issue
• cat /etc/passwd
• cat /proc/version
• env
• dpkg -l — list installed packages on Debian derived systems
• find
• getcap — find and list executable capabilities
• history
• hostname
• id
• ifconfig
• ip route
• last — display recently logged-in users (including IP addresses for network users)
• ls
• lsof -i — list programs using given network ports (use with netstat)
• netstat -ano — list all listening parts and established connections, no domain resolution
• netstat -i — list per interface statistics
• netstat -l — list only listening ports
• netstat -p — list protocol and service information (requires root to see everything)
• netstat -s — list protocol statistics
• ps auxfww — show process tree
• ps auxww — show lots and lots of process info
• rpm -qa — list installed packages on Red Hat derived systems
• sudo -l
• uname -a
• w — list all currently logged-in users and their current program
• who — list all currently logged-in users (including IP addresses for network users)