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🐧 Linux
Essential Linux commands and system administration
1. File and Directory Commands
What is it? These commands help you navigate and manage files in Linux. Like using File Explorer, but with text commands.
file_commands.sh
# pwd - show current directory
pwd
# ls - list files
ls # Simple list
ls -la # Detailed list with hidden files
# cd - change directory
cd /home # Go to home folder
cd .. # Go up one level
cd ~ # Go to user home
# mkdir - create folder
mkdir my_folder
# cp - copy file
cp file.txt file_copy.txt
# mv - move or rename
mv old_name.txt new_name.txt
# rm - delete
rm file.txt # Delete file
rm -r folder/ # Delete folder
# cat - show file content
cat file.txt
2. SSH - Secure Connection
What is it? SSH lets you connect to remote computers securely. Like having remote access to another computer.
ssh_guide.sh
# Connect to remote server
ssh user@example.com
# Connect with specific port
ssh -p 2222 user@example.com
# Generate SSH key (do this once)
ssh-keygen -t rsa -b 4096
# Copy key to server (for password-less login)
ssh-copy-id -i ~/.ssh/id_rsa.pub user@example.com
# Copy file from local to remote
scp file.txt user@example.com:/home/user/
# Copy file from remote to local
scp user@example.com:/home/user/file.txt .
3. Permissions - Control Access
What is it? Permissions control who can read, write, or run files. Important for security and organization.
permissions.sh
# chmod - change permissions
# Format: chmod [who][action][permission] file
# Numbers: r=4, w=2, x=1
chmod 755 file.sh # Owner: read+write+execute
# Group and Others: read+execute
chmod 644 file.txt # Owner: read+write
# Group and Others: read only
chmod 700 secret.txt # Only owner can access
# Make file executable
chmod +x script.sh
# chown - change owner
sudo chown user:group file.txt