Day 24: Performance Telemetry: CPU, Memory, Disk I/O & Load

Day 24 · Lunch — Performance Telemetry: CPU, Memory, Disk I/O & Load

⚡ 60-Second Mental Model (Student Digest)

╔══════════════════════════════════════════════════════════════════════════════╗
║  ZOTHOS × 1NC0GN30 // PRODUCTION TELEMETRY, SYSTEMD & RECOVERY MATRIX        ║
╠══════════════════════════════════════════════════════════════════════════════╣
║                                                                              ║
║   ┌──────────────┐   ┌──────────────┐   ┌──────────────┐   ┌──────────────┐  ║
║   │ CPU & SCHED  │   │ MEMORY / VM  │   │ DISK & VFS   │   │ NET SOCKETS  │  ║
║   │ top / mpstat │   │ free / vmstat│   │ iostat / df  │   │ ss -tulpen   │  ║
║   └──────┬───────┘   └──────┬───────┘   └──────┬───────┘   └──────┬───────┘  ║
║          └──────────────────┴─────────┬────────┴──────────────────┘          ║
║                                       ▼                                      ║
║                  [ Automated Remediation: systemd + cron + rsync ]           ║
╚══════════════════════════════════════════════════════════════════════════════╝

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🍽️ Day 24 Lunch: Writing Playbooks

Objective: Learn how to create and execute Ansible playbooks to automate system tasks across multiple machines.

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🖋️ Creating Your First Ansible Playbook

An Ansible playbook is a YAML file containing a list of actions (tasks) for Ansible to perform on managed nodes.

#### 📚 Example: Installing Nginx

- name: Install Nginx on webservers
  hosts: webservers
  become: yes
  tasks:
    - name: Ensure Nginx is installed
      apt:
        name: nginx
        state: present

Save this file as install_nginx.yml and run it using:

ansible-playbook -i hosts install_nginx.yml

---

🛠️ Managing Multiple Servers

To manage multiple servers:

1. Define groups in your inventory file:

[webservers]
192.168.1.10
192.168.1.11

[dbservers]
192.168.1.20

2. Target specific groups in playbooks using the hosts key.

This makes it easy to roll out updates or changes across a fleet of machines.

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🔹 Common Modules in Ansible

Modules are the building blocks of tasks in playbooks. Here are some commonly used ones:

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🤔 Practice Task

Create a playbook to:

* Update the package cache
* Install htop
* Ensure the htop service is running (if applicable)

- name: Install and run htop
  hosts: all
  become: yes
  tasks:
    - name: Update apt cache
      apt:
        update_cache: yes

    - name: Install htop
      apt:
        name: htop
        state: present

    - name: Run htop (verify presence)
      command: which htop

---

📚 Review Questions

1. What is a playbook and how is it structured?
2. How do you target specific groups of machines in your inventory?
3. What is the difference between the command and shell modules?
4. How would you install a package across multiple hosts?

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📖 Recommended Reading

* Ansible Playbooks - Official Docs
* Module Index
* Best Practices

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✅ Done?

Create your own playbook that installs multiple packages and configures a service, like setting up a basic web stack (nginx + ufw + fail2ban).

Next up: Dinner - Practical Ansible Labs

Day 24 · Dinner — Performance Telemetry: CPU, Memory, Disk I/O & Load

⚡ 60-Second Mental Model (Student Digest)

╔══════════════════════════════════════════════════════════════════════════════╗
║  ZOTHOS × 1NC0GN30 // PRODUCTION TELEMETRY, SYSTEMD & RECOVERY MATRIX        ║
╠══════════════════════════════════════════════════════════════════════════════╣
║                                                                              ║
║   ┌──────────────┐   ┌──────────────┐   ┌──────────────┐   ┌──────────────┐  ║
║   │ CPU & SCHED  │   │ MEMORY / VM  │   │ DISK & VFS   │   │ NET SOCKETS  │  ║
║   │ top / mpstat │   │ free / vmstat│   │ iostat / df  │   │ ss -tulpen   │  ║
║   └──────┬───────┘   └──────┬───────┘   └──────┬───────┘   └──────┬───────┘  ║
║          └──────────────────┴─────────┬────────┴──────────────────┘          ║
║                                       ▼                                      ║
║                  [ Automated Remediation: systemd + cron + rsync ]           ║
╚══════════════════════════════════════════════════════════════════════════════╝

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🍽️ Day 24 Dinner: Practical Ansible Labs

🎯 Objective

Reinforce your understanding of Ansible by completing hands-on lab exercises: writing playbooks, automating tasks, and debugging them effectively.

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🧪 Lab Task 1: Write Your First Playbook

✨ Goal

Create a simple playbook that performs a basic task, such as installing a package or creating a file.

🛠️ Example

- name: Create a file on localhost
  hosts: localhost
  connection: local
  tasks:
    - name: Create hello.txt file
      copy:
        dest: /tmp/hello.txt
        content: "Hello from Ansible!"

▶️ Run It:

ansible-playbook playbook.yml

---

🧪 Lab Task 2: Automate Software Installation

✨ Goal

Install and configure Nginx on multiple remote servers using Ansible.

🛠️ Example

- name: Install and start nginx
  hosts: webservers
  become: yes
  tasks:
    - name: Ensure Nginx is installed
      apt:
        name: nginx
        state: present

    - name: Ensure Nginx is running
      service:
        name: nginx
        state: started
        enabled: true

▶️ Run It:

ansible-playbook -i hosts install-nginx.yml

---

🧪 Lab Task 3: Playbook Debugging

✨ Goal

Learn to identify and fix errors in a failing playbook.

🛠️ Tools & Tips

* Add -v or -vvv for verbose error output
* Use the debug module to print variables
* Common issues:

* Indentation errors in YAML
* Wrong module arguments
* Incorrect hostnames or SSH keys

🔍 Debug Example

- name: Debug example
  hosts: localhost
  connection: local
  tasks:
    - name: Print debug message
      debug:
        msg: "This variable is {{ some_var }}"

Run it:

ansible-playbook debug-test.yml -e some_var=42

---

🧠 Review Questions

1. What does the become directive do in Ansible?
2. How can you make a playbook idempotent?
3. What’s the purpose of --check and --diff flags?
4. How can you limit execution to one host?

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📚 Additional Resources

* Ansible Labs from Red Hat
* Ansible Debug Module Docs
* YAML Syntax Guide

✅ Next Step: Create your own playbook to manage something on your local or remote systems. Try different modules like file, lineinfile, or cron!