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Ansible

Ansible is an automation tool that configures computers over SSH.

Instead of manually typing commands on every machine, you describe the desired state in a YAML file called a playbook, and Ansible makes the machine match that state.

In this section, Ansible is also used in a different way: it configures a mounted Raspberry Pi image through a chroot connection, not through SSH.

Install

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sudo apt install ansible

Build Raspberry Pi image with Ansible

Ansible playbook in nutshell

A playbook is a YAML file that tells Ansible what state a host should have.

Basic idea:

  • hosts: which machines from the inventory to configure
  • become: run tasks with sudo
  • tasks: ordered steps to apply
  • each task usually calls one Ansible module

Good playbooks are usually idempotent: running them again should not break the machine or repeat work that is already done.

simple_playbook.yml
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---
- name: Configure server
  hosts: all
  become: true

  tasks:
    - name: Install nginx
      ansible.builtin.apt:
        name: nginx
        state: present
        update_cache: true

    - name: Create welcome page
      ansible.builtin.copy:
        content: "hello from ansible\n"
        dest: /var/www/html/index.html
        mode: "0644"

Run it:

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ansible-playbook -i inventory.yml simple_playbook.yml

Common task examples

Install packages:

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- name: Install packages
  ansible.builtin.apt:
    name:
      - git
      - tmux
    state: present

Copy a file:

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- name: Copy config
  ansible.builtin.copy:
    src: app.conf
    dest: /etc/app.conf
    mode: "0644"

Create a directory:

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- name: Create app directory
  ansible.builtin.file:
    path: /opt/app
    state: directory
    mode: "0755"

Run a command:

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- name: Print kernel
  ansible.builtin.command:
    cmd: uname -r

Manage a service:

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- name: Enable and start nginx
  ansible.builtin.service:
    name: nginx
    state: started
    enabled: true

Most used tasks

Goal Module Short example
Install package ansible.builtin.apt name: nginx, state: present
Copy file ansible.builtin.copy src: app.conf, dest: /etc/app.conf
Create directory ansible.builtin.file path: /opt/app, state: directory
Run command ansible.builtin.command cmd: uname -r
Manage service ansible.builtin.service name: nginx, state: started
Template config ansible.builtin.template src: app.conf.j2, dest: /etc/app.conf