Base de Conhecimento

Ansible automates server configuration through simple, human-readable YAML files — letting you define your server's desired state once and apply it consistently across one or many servers, without manual SSH sessions.

Why Use Ansible

• Reproducible server configuration — no more "it worked on the old server but not the new one"
• Version-controlled infrastructure, reviewable like application code
• Apply the same configuration across multiple servers consistently
• Agentless — only requires SSH access, no software installed on managed servers

Prerequisites

• A control machine (your local machine or a dedicated management VPS) with Ansible installed
• SSH key access to the servers you want to manage

Step 1 — Install Ansible on the Control Machine

sudo apt install ansible -y

Step 2 — Create an Inventory File

mkdir ~/ansible-project && cd ~/ansible-project
nano inventory.ini

[webservers]
web1 ansible_host=203.0.113.10 ansible_user=deploy
web2 ansible_host=203.0.113.11 ansible_user=deploy

[databases]
db1 ansible_host=203.0.113.12 ansible_user=deploy

Step 3 — Test Connectivity

ansible all -i inventory.ini -m ping

Step 4 — Run an Ad-Hoc Command

ansible webservers -i inventory.ini -a "df -h" -b

-b (become) runs the command with sudo privileges.

Step 5 — Create Your First Playbook

nano setup-webserver.yml

---
- name: Configure web servers
  hosts: webservers
  become: true

  tasks:
    - name: Update apt cache
      apt:
        update_cache: yes

    - name: Install Nginx
      apt:
        name: nginx
        state: present

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

    - name: Allow HTTP and HTTPS through UFW
      ufw:
        rule: allow
        port: "{{ item }}"
      loop:
        - "80"
        - "443"

Step 6 — Run the Playbook

ansible-playbook -i inventory.ini setup-webserver.yml

Step 7 — Verify Idempotency

Run the playbook again — Ansible should report no changes needed the second time, since the desired state is already achieved. This idempotency is a core Ansible principle: running a playbook repeatedly should be safe and produce the same end result.

Using Variables

vars:
  app_port: 3000

tasks:
  - name: Deploy application
    template:
      src: app.service.j2
      dest: /etc/systemd/system/app.service

Organizing with Roles (For Larger Projects)

ansible-galaxy init roles/webserver

Roles let you organize related tasks, templates, and variables into reusable, shareable units — useful once your playbooks grow beyond a single file.

Example: Applying Server Hardening via Ansible

tasks:
  - name: Disable root SSH login
    lineinfile:
      path: /etc/ssh/sshd_config
      regexp: '^PermitRootLogin'
      line: 'PermitRootLogin no'
    notify: restart sshd

handlers:
  - name: restart sshd
    systemd:
      name: sshd
      state: restarted

Common Errors

"UNREACHABLE" error — verify SSH connectivity manually first: ssh [email protected]; Ansible relies entirely on working SSH access.

Permission errors on tasks requiring sudo — ensure become: true is set at the playbook or task level.

Best Practices

• Keep playbooks version-controlled alongside your application code
• Design tasks to be idempotent — safe to run repeatedly
• Use roles to organize configuration as your infrastructure grows

Continue Reading

• How to Version Control Your Server Configuration
• How to Harden a Fresh Linux VPS in 15 Minutes
• Infrastructure as Code Basics: Managing VPS Config with Terraform

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