essential_commands.md

Essential Ubuntu Linux Commands

System Information

• uname -a – display kernel and OS info
• lsb_release -a – Ubuntu version details
• hostnamectl – show hostname and hardware info

Filesystem Navigation

• ls -la – list all files with permissions
• cd /path/to/dir – change directory
• pwd – print working directory
• tree – directory tree (install with sudo apt install tree)

File Operations

• cp source dest – copy files
• mv source dest – move/rename files
• rm file – delete file (use -r for directories)
• chmod 755 file – change permissions
• chown user:group file – change ownership

Package Management (APT)

• sudo apt update – refresh package lists
• sudo apt upgrade – upgrade installed packages
• sudo apt install package_name – install a package
• sudo apt remove package_name – remove a package
• apt search keyword – search for packages

System Monitoring

• top / htop – view running processes
• df -h – disk space usage
• free -h – memory usage
• systemctl status service – check service status

Networking

• ip a – show network interfaces
• ping hostname – test connectivity
• netstat -tulpn – list listening ports
• sudo apt install net-tools – provides netstat

User Management

• adduser username – create new user
• deluser username – delete user
• usermod -aG sudo username – add to sudo group

Service Management (systemd)

• sudo systemctl start service
• sudo systemctl stop service
• sudo systemctl enable service
• sudo systemctl disable service

Miscellaneous

• cat file – display file contents
• grep 'pattern' file – search within files
• sudo shutdown -h now – immediate shutdown
• sudo reboot – reboot system

Tip: Most commands have --help for usage details, and you can use the man pages (man <command>).