1. Basic Navigation
1.1 cd: Change Directory
# Change to an absolute path
cd /study/files
# Change to a relative path
cd test/
# Special directory shortcuts
cd . # Current directory
cd .. # Parent directory
cd / # Root directory
cd ~ # Home directory
1.2 ls: List Directory Contents
# Basic listing
ls
# Detailed listing
ls -l
# Alias for detailed listing
ll
1.3 pwd: Print Working Directory
# Show current directory path
pwd
2. System Information
2.1 hostname: Display Host Name
hostname
2.2 who: Show Logged-in Users
who
2.3 whoami: Display Current Usenrame
whoami
2.4 ifconfig: Show Network Interface Configuration
ifconfig
2.5 ping: Test Network Connectivity
ping example.com
3. File and Dircetory Operations
3.1 mkdir: Create Directories
# Create a single directory
mkdir /usr/local/Test
# Create nested directories
mkdir -p parent/child/grandchild
3.2 touch: Create Empty Files
# Create a file with extension
touch document.txt
3.3 vi: Text Editor
# Open file for editing
vi document.txt
# Editing commands:
# i - Enter insert mode
# ESC - Exit insert mode
# :wq - Save and quit
# :q - Quit (if no changes)
# :q! - Force quit without saving
3.4 cp: Copy Files and Directories
# Copy a file
cp source.txt destination/
# Copy a directory recursively
cp -r source_dir/ destination/
3.5 mv: Move or Rename
# Move a file
mv file.txt new_location/
# Rename a file
mv old_name.txt new_name.txt
3.6 rm: Remove Files and Directories
# Remove a file
rm unwanted_file.txt
# Remove a directory recursively and forcefully
rm -rf unwanted_directory/
# Common options:
# -r: Recursive removal
# -f: Force removal
# -v: Verbose output
# -i: Interactive prompt
3.7 chmod: Change File Permissions
# Change permissions using numeric notation
chmod 755 script.sh
# Change permissions recursively
chmod -R 644 directory/
# Permission values:
# r (read) = 4
# w (write) = 2
# x (execute) = 1
# Example: r-x = 5 (4+1)
3.8 tar: Archive and Compress
# Create a tar archive
tar -cvf archive.tar source_dir/
# Extract a tar archive
tar -xvf archive.tar
# Create a compressed tar archive
tar -zcvf archive.tar.gz source_dir/
# Extract a compressed tar archive
tar -zxvf archive.tar.gz
# Common options:
# c: Create archive
# x: Extract archive
# z: Use gzip compression
# v: Verbose output
# f: Specify filename
4. File Viewing and Searching
4.1 cat: Display File Contents
cat document.txt
4.2 head: View Beginning of File
# Show first 5 lines
head -5 document.txt
4.3 sed: Extract Specific Lines
# Show lines 5 through 10
sed -n '5,10p' document.txt
4.4 tail: View End of File
# Show last 5 lines
tail -5 document.txt
# Follow file changes in real-time
tail -f logfile.log
4.5 more: View File Page by Page
# View file with pagination
more document.txt
# Start from line 20
more +20 document.txt
4.6 less: Advanced File Viewer
# View file with navigation
less document.txt
4.7 grep: Search Text Patterns
# Basic search
grep "search_term" file.txt
# Case-insensitive search
grep -i "term" file.txt
# Show line numbers
grep -n "term" file.txt
# Search in multiple files
grep "term" *.txt
# Search with color highlighting
grep --color=auto "term" file.txt
4.8 find: Search for Files
# Find file by name
find /usr/local -name "TargetFile"
# Find files with pattern
find /usr/local -name "test*"
4.9 |: Pipe Operator
# Chain commands: find version in last 200 lines
tail -200 log.txt | grep "version"
4.10 Redirection Operators
# Overwrite file
command > output.txt
# Append to file
command >> output.txt
# Force overwrite
command >! output.txt
# Input from file
command < input.txt
5. User and Group Management
5.1 User Management
# Create a new user
useradd newuser
# Set user password
passwd newuser
# Delete a user
userdel olduser
# Delete user with home directory
userdel -r olduser
# View all users
cat /etc/passwd
5.2 Group Management
# Create a new group
groupadd developers
# Delete a group
groupdel developers
# Add user to group
gpasswd -a username developers
# Remove user from group
gpasswd -d username developers
# Check user's groups
groups username
# View all groups
cat /etc/group
