Linux Command Line Basics: Essential Commands for Beginners

The Linux command line (terminal/shell) is the primary interface for managing servers. Understanding essential commands is fundamental for VPS and Dedicated server administration at UnderHost.

Navigation: cd, pwd, ls

pwd - Print working directory (shows current location):

$ pwd
/home/username/public_html

ls - List directory contents:

$ ls                  # List files in current directory
$ ls -la              # List with details and hidden files (-a shows hidden, -l is long format)
$ ls -lh              # Human-readable file sizes

cd - Change directory:

$ cd /var/www         # Go to absolute path
$ cd ..               # Go to parent directory
$ cd ~                # Go to home directory
$ cd -                # Go to previous directory

File Management: cp, mv, rm

cp - Copy files:

$ cp file.txt file-copy.txt        # Copy file
$ cp -r directory/ directory-copy/ # Copy directory recursively

mv - Move or rename:

$ mv oldname.txt newname.txt    # Rename file
$ mv file.txt /home/backup/    # Move file to directory

rm - Delete (CAUTION: no recovery):

$ rm file.txt        # Delete file
$ rm -r directory/   # Delete directory and contents
$ rm -f file.txt     # Force delete (no confirmation)

Viewing Files: cat, less, tail

cat - Display entire file:

$ cat filename.txt

less - View file with pagination (scroll with arrow keys, 'q' to quit):

$ less logfile.txt

tail - View last lines (useful for logs):

$ tail logfile.txt           # Last 10 lines
$ tail -20 logfile.txt       # Last 20 lines
$ tail -f logfile.txt        # Follow in real-time (Ctrl+C to stop)

Permissions: chmod, chown

chmod - Change file permissions (755 = rwxr-xr-x):

$ chmod 755 script.sh    # Make executable (owner: all, others: read+execute)
$ chmod 644 file.txt    # Readable but not executable
$ chmod -R 755 dir/     # Change directory and all contents

chown - Change file owner:

$ sudo chown user:group file.txt    # Change owner and group
$ sudo chown -R user:group dir/    # Recursively

System Information

Common system info commands:

$ whoami              # Current user
$ hostname            # Server name
$ uname -a            # System information
$ df -h               # Disk space usage
$ free -h             # RAM usage
$ top                 # Real-time system stats (Ctrl+C to exit)
$ ps aux              # List running processes

Text Editing: nano, vi

nano - Simple text editor (recommended for beginners):

$ nano filename.txt
# Edit, then press Ctrl+O (save), Ctrl+X (exit)

vi/vim - Powerful but steeper learning curve:

$ vi filename.txt
# Press 'i' to insert/edit
# Press Esc, then ':wq' to save and exit
# Press Esc, then ':q!' to exit without saving

Pipes and Redirects

Redirect output to file (> overwrites, >> appends):

$ ls > files.txt       # Save output to file
$ echo "text" >> file.txt  # Append to file

Pipe (|) - send output from one command to another:

$ ps aux | grep nginx   # Find nginx process
$ ls -la | wc -l        # Count files

Wildcards and Globbing

Common wildcards:

$ ls *.txt              # All .txt files
$ ls file?.txt          # file1.txt, file2.txt (single character)
$ ls [abc]*.txt         # Files starting with a, b, or c

Related: Bash scripting | SSH connection | File permissions detailed

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