________________________________________________________________________________
       
       Module 3: System Plumbing (Monitoring & Networking)
       ________________________________________________________________________________
       
       Now that you know how to navigate and lock doors, you need to see what's 
       happening under the hood. This module is about Performance and Connectivity.
       
       1. The "Task Manager" of Linux
       
       How do you know if your system is lagging because of the CPU, RAM, or a specific
       program?
       
       top: The classic system monitor. It shows real-time CPU and RAM usage. (Press q 
       to exit).
       htop: A much prettier, interactive version of top. (You might need to install 
       it: sudo apt install htop).
       df -h: Shows how much Disk Space you have left in "human-readable" format.
       free -m: Shows your RAM usage in Megabytes.
       
       /-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=/
       
       2. Managing Processes
       
       Every program running is a "Process" with a unique PID (Process ID).
       
       ps aux: Lists every single process running on the system.
       kill [PID]: Stops a runaway process. (It’s like "End Task" in Windows).
       kill -9 [PID]: The "I didn't ask, I'm telling you" version of kill. It forces 
       the process to stop immediately.
       
       /-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=/
       
       3. Services (Systemd)
       
       In Linux, background programs (like web servers or databases) are called
       Services.
       
       sudo systemctl start [service]: Start a service.
       sudo systemctl stop [service]: Stop it.
       sudo systemctl status [service]: See if it's running or if it crashed.
       
       /-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=/
       
       4. Networking Basics
       
       ip addr: Shows your IP address. (The old command was ifconfig, but ip addr 
       is the modern standard).
       ping [website]: Checks if you have a connection to the outside world.
       ssh [user]@[ip-address]: How you remotely log into another Linux machine.
       
       /-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=/
       
       Module 3 Practical Challenge
       
       This one is a bit more "hands-on."
       
       Find a Target: Run top and find the PID of any process (doesn't matter 
       which one, maybe just the top process itself).
       Check Space: Use df -h to find out which "partition" (the things listed 
       under Filesystem) is the largest.
       
       Install a Service: Install the Apache web server:
       
       sudo apt update
       sudo apt install apache2 (or httpd if you're on Rocky/Fedora).
       Control the Service: * Check its status (systemctl status apache2).
       Stop it.
       Check the status again to confirm it's "inactive."
       
       Find Yourself: Use ip addr to find your "eth0" or "enp0s3" IP address.
       
       _______________________________________________________________________________
       
 (DIR) Module 1
 (DIR) Module 2
 (DIR) Module 3
 (DIR) Module 4
 (DIR) Back to Home