Linux Learning Resources - Practical Guides

chmod u+x my_script.sh        # Add execute permission for owner
chmod go-w sensitive_file.txt # Remove write permission from group & others
chmod a=r new_document.txt    # Set read-only for everyone
chmod +x my_script.sh         # Add execute for all

chmod 755 my_script.sh    # Executable scripts and directories
chmod 644 my_file.txt     # Regular files (owner modify, others read)
chmod 700 private_folder/ # Only owner can access

chown newuser file.txt           # Change user owner to 'newuser'
chown -R newuser directory/      # Change owner recursively
chown newuser:newgroup file.txt  # Change both user and group owner

chgrp newgroup file.txt          # Change group owner to 'newgroup'
chgrp -R newgroup directory/     # Change group recursively

whoami    # Show your current username (e.g., 'root')

id        # Show user ID (UID), group ID (GID), and all groups
id user   # Show details for a specific user

adduser newuser       # Create a new user account (interactive)

deluser username      # Delete user, keeps home directory
deluser -r username   # Delete user AND their home directory

passwd                # Change your own password
passwd username       # Change another user's password (as root)

groups                # Show groups of the current user
groups username       # Show groups of 'username'

ls          # List directory contents
            - ls          (List files)
            - ls -l       (Long format, shows details)
            - ls -a       (Show all files, including hidden)
            - ls -alF     (Detailed view with indicators)

pwd         # Print working directory (show current location)

cd          # Change directory
            - cd <dirname>  (Go into specific directory)
            - cd ..         (Go up one directory level)
            - cd            (Go to home directory)
            - cd /          (Go to root directory)

mkdir       # Make directory (create new folder)
            - mkdir my_folder
            - mkdir -p parent/child  (Create parent if needed)

rmdir       # Remove empty directory
            - rmdir empty_folder

touch       # Create empty file or update timestamp
            - touch my_file.txt

cp          # Copy files or directories
            - cp source.txt destination.txt
            - cp -r my_folder/ new_location/

mv          # Move or rename files or directories
            - mv old_name.txt new_name.txt
            - mv file.txt /path/to/new_location/

rm          # Remove (delete) files or directories (USE WITH CAUTION!)
            - rm unwanted_file.txt
            - rm -r unwanted_folder/
            - rm -rf dangerous_folder/  (Force remove - BE CAREFUL!)

cat         # Concatenate and display file content (good for small files)
            - cat my_file.txt

less        # View file page by page (good for large files)
            - less large_log_file.log
            - (Press Space to scroll, 'q' to quit)

head        # Display beginning of a file
            - head file.txt        (First 10 lines)
            - head -n 5 file.txt   (First 5 lines)

tail        # Display end of file (useful for logs)
            - tail log_file.log       (Last 10 lines)
            - tail -n 20 log_file.log (Last 20 lines)
            - tail -f log_file.log    (Follow new lines)

grep        # Search for patterns in files
            - grep "keyword" my_file.txt
            - grep -i "keyword" my_file.txt (Case-insensitive)
            - grep -r "keyword" /path/to/folder (Recursive)

find        # Search for files and directories
            - find . -name "*.txt"
            - find / -type d -name "config"

whoami      # Show current logged-in username

id          # Show user ID, group ID, and all groups

date        # Display current date and time

clear       # Clear the terminal screen

history     # Show your command history
            - !<number>  (Run command from history)
            - !<string>  (Run last command starting with string)

echo        # Display a line of text
            - echo "Hello, Linux!"
            - echo $PATH  (Display environment variable)

man         # Manual pages - get detailed help
            - man ls  (Shows manual for 'ls' command)

apk         # Alpine Linux package manager
            - apk update           (Update list of packages)
            - apk add <package>    (Install a package)
            - apk search <keyword> (Search for packages)

poweroff    # Shut down the system cleanly

reboot      # Restart the system cleanly

exit        # Exit the current shell session (logs you out)

ping google.com    # Ping a website
ping 8.8.8.8       # Ping a public DNS server by IP address

ip a          # Display network interfaces and their IP addresses
ip addr       # Alternative syntax

ip r          # Show kernel routing table
ip route      # Alternative syntax

curl example.com                    # Fetch HTML content
curl -O google.com/index.html       # Download index.html
curl ifconfig.me                    # Show your external IP address

alpine:~# curl example.com
<!doctype html>
<html>
<head>
    <title>Example Domain</title>
... (HTML content will scroll by)

ls -la              # List all files with details
pwd                 # Show current directory
cd /path            # Change directory
mkdir dirname       # Create directory
rm -rf dirname      # Delete directory (use with caution!)
cp file1 file2      # Copy file
mv file1 file2      # Rename/move file
cat file            # Display file content
grep pattern file   # Search in file
find . -name "*.txt" # Find files by pattern
chmod 755 file      # Change permissions (executable)
chmod 644 file      # Change permissions (regular file)
chown user:group file # Change ownership

whoami              # Current user
id                  # User and group IDs
adduser newuser     # Create new user
passwd              # Change password
groups              # Show user's groups
date                # Show date/time
df -h               # Disk space usage
free -h             # Memory usage
ps aux              # List running processes
top                 # System monitor

apk update          # Update package database
apk search package  # Search for package
apk add package     # Install package
apk del package     # Remove package
apk info            # List installed packages

ping 8.8.8.8        # Test connectivity
ip a                # Show IP addresses
ip r                # Show routing table
curl example.com    # Fetch URL