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User and Group Management

• passwd – Changes the password of a user account.
  • Example: sudo passwd username
• useradd – Creates a new user account.
  • Example: sudo useradd -m newuser
• userdel – Deletes a user account.
  • Example: sudo userdel username
• usermod – Modifies a user account, such as changing the username or group.
  • Example: sudo usermod -aG sudo username
• groupadd – Creates a new group.
  • Example: sudo groupadd newgroup
• groupdel – Deletes a group.
  • Example: sudo groupdel oldgroup
• groups – Displays the groups a user is a member of.
  • Example: groups username
• id – Displays user and group information for a specified user.
  • Example: id username

Package Manager

• apt-get – A command-line tool to handle packages on Debian-based systems, used to install, remove, or upgrade packages.
  • Example: sudo apt-get install curl
• apt – A newer, simpler front-end for the apt-get tool for package management on Debian-based systems.
  • Example: sudo apt update
• yum – Package management tool for RPM-based Linux distributions (like CentOS, Red Hat), used to install, update, or remove packages.
  • Example: sudo yum install curl
• dnf – A newer package manager for RPM-based systems, replacing yum in many distributions (like Fedora).
  • Example: sudo dnf install curl
• rpm – Command-line tool to install, remove, and query RPM packages.
  • Example: sudo rpm -ivh package.rpm
• dpkg – The low-level package manager for Debian-based systems that installs and manages .deb packages.
  • Example: sudo dpkg -i package.deb
• snap – A package management system for installing snaps (self-contained applications) across various Linux distributions.
  • Example: sudo snap install vlc
• zypper – Package manager for openSUSE, used to install, update, and manage packages.
  • Example: sudo zypper install curl

Network Configuration & Monitoring

• ifconfig – Displays and configures network interfaces (deprecated in favor of ip).
  • Example: ifconfig eth0
• ip add – Displays IP addresses of network interfaces (part of the ip tool suite).
  • Example: ip addr show
• ping – Sends ICMP echo requests to test network connectivity.
  • Example: ping 8.8.8.8
• netstat – Displays network connections, routing tables, and interface statistics (deprecated in favor of ss).
  • Example: netstat -tuln
• ss – A utility to investigate sockets and network connections, replacing netstat.
  • Example: ss -tuln
• traceroute – Traces the route packets take to a network host, showing each hop along the way.
  • Example: traceroute google.com
• ssh – Securely connects to a remote system using the SSH protocol.
  • Example: ssh user@hostname
• nc – Netcat, a utility for reading/writing network connections, useful for port scanning, listening, and sending data.
  • Example: nc -zv 192.168.1.1 1-1000

Process Management

• ps – Displays a snapshot of current running processes.
  • Example: ps aux
• top – Displays dynamic real-time information about processes.
  • Example: top
• kill – Sends a signal to terminate a process by its PID (process ID).
  • Example: kill 1337
• killall – Sends a signal to terminate processes by name.
  • Example: killall firefox
• pstree – Displays processes in a tree-like format, showing their hierarchy.
  • Example: pstree
• htop – Interactive version of top, providing a more user-friendly, color-coded view of processes.
  • Example: htop

File and Directory Management

• ls – Lists the contents of a directory.
  • Example: ls -l /home/user
• pwd – Displays the current working directory.
  • Example: pwd
• cd – Changes the current directory.
  • Example: cd /home/user/Documents
• mkdir – Creates a new directory.
  • Example: mkdir newdir
• mdir – Similar to mkdir, but used for creating directories on remote systems (e.g., with FTP).
  • Example: mdir /mnt/remote/dir
• touch – Creates an empty file or updates the timestamp of an existing file.
  • Example: touch newfile.txt
• cp – Copies files or directories.
  • Example: cp file1.txt file2.txt
• mv – Moves or renames files or directories.
  • Example: mv oldname.txt newname.txt
• rm – Removes files or directories. There are several options for the rm command as well (ie -force (-f), -recursive (-r), -verbose (-v), -interactive (-i))
  • Example: rm file.txt

File Viewing and Editing

• cat – Concatenates and displays file content.
  • Example: cat file.txt
• less – Displays file content one screen at a time, allowing scrolling backward and forward.
  • Example: less file.txt
• more – Similar to less, but less feature-rich (only allows forward scrolling).
  • Example: more file.txt
• nano – A simple, text-based text editor.
  • Example: nano file.txt
• vim – A powerful text editor with advanced features for editing files.
  • Example: vim file.txt
• gedit – A graphical text editor for GNOME-based systems.
  • Example: gedit file.txt

System Information

• uname – Displays system information, such as the kernel version and architecture.
  • Example: uname -a
• df – Displays disk space usage for all mounted filesystems.
  • Example: df -h
• du – Displays disk usage for files and directories.
  • Example: du -sh /home/user
• free – Displays memory usage, including free and used memory.
  • Example: free -h
• lscpu – Displays detailed information about the CPU architecture.
  • Example: lscpu
• lshw – Displays detailed hardware configuration information.
  • Example: sudo lshw -short
• lsblk – Lists information about block devices (e.g., hard drives and partitions).
  • Example: lsblk

Permission Commands

• chmod – Changes the file or directory permissions.
  • Example: chmod u+x file.txt
• chown – Changes the owner and/or group of a file or directory.
  • Example: sudo chown user:group file.txt
• chgrp – Changes the group ownership of a file or directory.
  • Example: sudo chgrp admin file.txt
• umask – Sets default file creation permissions.
  • Example: umask 022
• setfacl – Sets file access control lists for more granular permission control.
  • Example: setfacl -m u:username:rwx file.txt
• getfacl – Displays the access control list (ACL) of a file or directory.
  • Example: getfacl file.txt
• chattr – Changes file attributes for advanced file protection (e.g., immutability).
  • Example: sudo chattr +i file.txt
• ls -l – Lists files and directories with detailed information, including permissions.
  • Example: ls -l file.txt