Linux Commands

Mastering Linux Commands: Your Essential Guide to the Command Line

Topic: Linux CLI Basics | Skills Covered: File Management, Process Handling, Networking, Permissions | Level: Beginner to Intermediate

Linux offers a powerful Command Line Interface (CLI) that provides direct access to system operations and configurations. This guide covers everything from basic file commands to user management and networking. Whether you're a beginner or brushing up your skills, these commands will sharpen your terminal prowess. Explore Advanced Linux Tutorials for deeper insights.

📁 File and Directory Commands

• ls, ls -l, ls -a – List contents, long format, show hidden files
• pwd – Print current directory
• cd /path/to/dir – Change directory
• mkdir new_folder – Create a new directory
• rmdir empty_folder – Remove an empty directory
• rm -r folder – Delete directory and contents
• touch file.txt – Create an empty file
• cp src dest – Copy files or directories
• mv src dest – Move or rename files
• rm file.txt – Delete a file
• find /path -name "pattern" – Search for files
• tree – View directory structure (may need to install)

📄 File Viewing and Editing

• cat, less, more – View contents of files
• head, tail – View first or last 10 lines
• nano file, vim file – Edit files in terminal
• echo "text" – Print text
• echo "text" > file – Overwrite file
• echo "text" >> file – Append to file

👤 User Management

• whoami – Show current user
• id – Show UID, GID
• adduser newuser – Add a new user
• passwd username – Change password
• su user – Switch to another user
• sudo command – Execute as superuser
• logout – Log out of session
• export FLINK_HOME=/opt/flink/flink-2.0.0 Setting Environment Variables:
• export PATH=/opt/flink/flink-2.0.0/bin:$PATHUpdate the path variable with additional value
• echo $PATH Printing Variable on console.
• echo $FLINK_HOME Prin Variable on console.

📦 Package Management

• Debian/Ubuntu: apt based
  sudo apt update – Update repo
  sudo apt install curl – Install a package
  sudo apt remove nano – Remove a package
• RHEL/CentOS: yum or dnf
sudo yum install httpd
sudo dnf install git

⚙️ System Information

• uname -a – System details
• top, htop – View running processes
• df -h – Disk usage
• free -h – Memory usage
• uptime – System uptime
• who – Who is logged in

📂 Permissions and Ownership

• ls -l – View file permissions
• chmod 755 file.sh – Set file permissions
• chmod +x file.sh – Make a file executable
• chown user:group file – Change file owner

Warning: Use chmod and sudo cautiously. Incorrect permissions can break your system or create security holes.

🔍 Searching and Filtering

• grep "text" file – Find text in a file
• grep -r "pattern" /dir – Recursive search
• find /path -name "*.sh" – Locate by name
• locate filename – Search indexed files

🧰 Networking Commands

• ping example.com – Check connectivity
• ip a or ifconfig – Network details
• netstat -tulpn – Listening ports
• curl http://example.com – Fetch page content
• wget https://url/file.zip – Download file
• hostname – Display hostname

💻 Process Management

• ps, ps aux – Show processes
• kill 1234 – Terminate process by PID
• kill -9 1234 – Force kill
• xkill – Click to kill window (GUI)

🧪 Archive and Compression

• tar -czvf archive.tar.gz folder/ – Compress folder
• tar -xvf archive.tar.gz – Extract archive
• unzip file.zip – Unzip file
• gzip file – Compress file
• gunzip file.gz – Decompress

🧮 Disk and Mounting

• mount /dev/sdX /mnt – Mount device
• umount /mnt – Unmount device
• lsblk – List block devices
• fdisk -l – View partitions

⛔ Shutdown and Reboot

• shutdown now – Immediate shutdown
• reboot – Restart system
• shutdown -r now – Reboot now
• halt – Halt system

Example Workflow for Create/Edit File

• vi notes.txt – Step 1: open/create file
• i – Step 2: enter insert mode
• Type your text... – Step 3: edit text
• Esc. – Step 4: go back to normal mode
• :wq or ZZ – Step 5: save and exit
• :w – save the file
• :q – quit (only if no changes)
• :q! – Quit without saving (force exit)

✅ 3. Enter Insert Mode to Type or Edit. Press i to go into Insert Mode, Other ways to enter Insert Mode:

• i – insert at cursor
• I – insert at beginning of line
• a – append after cursor
• A – append at end of line
• o – open new line below
• O – open new line above

Ready for more? Explore Our Advanced Linux Guide | Practice safely in a VM first!

📘 Linux Command FAQs

Q1. How do I undo a command in Linux?
A: There's no built-in undo. Use rm -i and double-check commands.

Q2. What's the difference between sudo and su?
A: sudo runs a single command as superuser. su changes your session to another user (often root).