Always start your script with #!/bin/bash. That first line is called a shebang (#!). It tells Linux which program should run the script. Without it, your script might not run correctly. Example: #!/bin/bash echo "Hello, world!" Steps to run it: Save it as hello.sh. Make it executable: chmod +x hello.sh Run it: ./hello.sh Output: Hello, world! 👉 Without the #!/bin/bash line, Linux will use the shell of the session you are logged into.

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The /etc/hosts file is a fundamental system file that plays a key role in how your Linux machine resolves domain names to IP addresses. It's essentially a local, manually managed DNS table. When you type a hostname like www.google.com into your browser, your system first checks /etc/hosts to see if there's a corresponding IP address listed there before sending a query to an external DNS server. This local check makes resolution extremely fast since no network communication is required. 🎯 Primary Uses * Blocking Websites: This is a common use for parents or system administrators. By mapping a domain to your local machine's loopback address (127.0.0.1), you can effectively prevent access to a site. For example, adding 127.0.0.1 twitter.com will block access to Twitter on your machine. * Local Development: Developers use the hosts file to test web applications before they go live on a public server. By adding an entry like 192.168.1.10 myapp.local, they can access their development server using a user-friendly hostname instead of an IP address. This mimics a live environment. * Network Shortcuts: You can create simple, memorable hostnames for devices on your local network. Instead of remembering 192.168.1.50 for your network printer, you could add 192.168.1.50 printer to your hosts file and simply type printer into your browser or command line to access it. ✍️ Editing the File The /etc/hosts file requires root permissions to edit. You can use a text editor like nano or vim with the sudo command. A good practice is to always back up the original file before making any changes. * Backup: sudo cp /etc/hosts /etc/hosts.bak * Edit: sudo nano /etc/hosts * Add your entries: Add new lines with the format IP_address hostname. * Save and Exit: Press Ctrl+O to save and Ctrl+X to exit in nano. After editing and saving, the changes take effect immediately without needing to restart any services. 🛡️ Important Notes * Comments: Lines starting with a # are ignored by the system and can be used to add comments for clarity. For example, # Blocked for security.