Day 58: Ansible Playbooks  (Jan 23, 2024)

Day 58: Ansible Playbooks (Jan 23, 2024)

🙏 Introduction:

In this blog, we'll explore Ansible Playbooks

🔶What is Ansible Playbooks

Ansible playbooks run multiple tasks, assign roles, and define configurations, deployment steps, and variables. If you’re using multiple servers, Ansible playbooks organize the steps between the assembled machines or servers and get them organized and running in the way the users need them to. Consider playbooks as the equivalent of instruction manuals.

🎯Task: 1

  1. Write an ansible playbook to create a file on a different server

  • Create an inventory file for Ansible

  • Create a file with name create_file.yml
---
- name: Create file on hosts
  hosts: all
  become: yes

  tasks:
    - name : create a file
      file :
        path: /home/ubuntu/test.txt
        state: touch

  • In this playbook, we define a single task that uses the file module to create the file

  • Path parameter specifies the full path to the file we want to create

  • State parameter set to touch which will create the file if it doesn't exist and do nothing if it does exist.

  • Now we will run this playbook using the ansible-playbook command

ansible-playbook file-name.yml -i <inventory-file-path> --private-key=<private-key-path>
ansible-playbook create_file.yml -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

  • Verify that the file has been created on different servers
ansible all -a "ls /home/ubuntu" -i <inventory-file> --private-key=<key-path>
ansible all -a "ls /home/ubuntu" -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

  1. Write an ansible playbook to create a new user

  • Create a file with name create_user.yml
---
- name: create user on hosts
  hosts: all
  become: yes

  tasks:
  - name: create a user
    user: name=test_user

  • In this playbook, we define a single task that uses the user module to create the new user
ansible-playbook file-name.yml -i <inventory-file-path> --private-key=<private-key-path>
ansible-playbook create_user.yml -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

  • To check if the user has been created, look for the user's name in the /etc/passwd
ansible server1  -a "cat /etc/passwd" -i <inventory-file-path>
ansible server1  -a "cat /etc/passwd" -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

  1. Write an ansible playbook to install docker on a group of servers

  • Create a file with name install_docker.yml
---
- name: This playbook will install Docker
  hosts: all
  become: true  
  tasks:
  - name: Add Docker GPG apt Key
    apt_key:
     url: https://download.docker.com/linux/ubuntu/gpg
     state: present

  - name: Add Docker Repository
    apt_repository:
      repo: deb https://download.docker.com/linux/ubuntu focal stable
      state: present

  - name: Install Docker
    apt:
      name: docker-ce
      state: latest

  • In this playbook, we define three tasks that install Docker on a group of servers, hosts parameter specifies the group of servers where Docker will be installed, become parameter is set to yes, which means that the tasks will use elevated privileges to install Docker.

  • The first task adds the Docker GPG key to the apt keyring, which is required for package signature verification.

  • The second task adds the Docker repository to the list of sources used by apt-get. This allows the system to download Docker packages from the Docker repository.

  • The final task installs Docker using the apt module. We specify the package name as docker-ce, which installs the Community Edition of Docker.

ansible-playbook file-name.yml -i <inventory-file-path> --private-key=<private-key-path>
ansible-playbook install_docker.yml -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

  • Verify that Docker has been installed on multiple servers
ansible all -a "docker --version" -i <inventory-path> --private-key=<key-path>
ansible all -a "docker --version" -i /home/ubuntu/ansible/hosts --private-key=/home/ubuntu/.ssh/ansible_key

🎯Task: 2

Write a blog about writing ansible playbooks with the best practices

Ansible is a powerful open-source automation tool that allows you to automate IT infrastructure management. Ansible playbooks are the configuration files that describe the desired state of your systems. Writing Ansible playbooks with best practices can make your automation more robust, reliable, and scalable. In this blog, we will discuss some best practices for writing Ansible playbooks.

Use a clear structure:

Make sure your playbook is organized and easy to read. Use comments and section headers to explain what each part of the playbook does. Avoid nesting too many tasks or plays inside each other, as it can make the playbook difficult to read and maintain.

Use idempotent tasks:

Idempotency is one of the key principles of Ansible. It means that a task should be designed in such a way that it can be executed repeatedly without changing the state of the system. This makes your playbook more robust and prevents unexpected changes to the system. You can achieve idempotency by using modules that are designed to be idempotent, such as apt, yum, and copy.

Example:

- name: Install Apache web server
  apt:
    name: apache2
    state: latest

In this example, the apt module will only install the Apache web server if it is not already installed or if there is a newer version available.

Use variables:

Variables can make your playbook more flexible and reusable. They allow you to store values that can be used across multiple tasks and playbooks. You can define variables in the playbook itself or in separate files, such as group_vars or host_vars.

Example:

- name: Install Nginx web server
  apt:
    name: nginx
    state: latest

- name: Configure Nginx web server
  template:
    src: nginx.conf.j2
    dest: /etc/nginx/nginx.conf
  vars:
    nginx_port: 80

In this example, we are using a variable nginx_port to define the port number used by Nginx. The variable is defined in the vars section of the template task.

Use roles:

Roles are a way to organize your tasks, variables, and files into reusable components. They can be used across multiple playbooks and provide a way to share functionality between different teams. Roles can also make your playbook more modular and easier to maintain.

Example:

- name: Install web serve
  hosts: all
  roles:
    - webserver

In this example, we are using a role called webserver to install the web server on the all group of hosts.

Use tags:

Tags allow you to selectively run specific tasks or groups of tasks within a playbook. This can be useful when testing or debugging your playbook or when you need to run a subset of tasks. Tags can be added to individual tasks or to entire plays.

Example:

- name: Install web serve
  hosts: all
  become: yes
  tags:
    - webserver


  tasks:
    - name: Install Apache web server
      apt:
        name: apache2
        state: latest
      tags:
        - apache


    - name: Install Nginx web server
      apt:
        name: nginx
        state: latest
      tags:
        - nginx

In this example, we are using tags to selectively run the Apache or Nginx installation tasks.

Use conditionals:

Conditionals allow you to execute a task only if a specific condition is met. This can be useful when you need to run a task only on a subset of hosts or when you need to run a task only if a specific variable is defined.

Example:

---
- name: Example playbook with a conditional
  hosts: all
  vars:
    myvar: "foo"
  tasks:
    - name: Task 1
      debug:
        msg: "This task will always run"

    - name: Task 2
      debug:
        msg: "This task will run if myvar equals 'foo'"
      when: myvar == "foo"

In this example, the playbook has two tasks. Task 1 will always run because it doesn't have a conditional attached to it. Task 2 will only run if the variable myvar is equal to "foo". If myvar has any other value, Task 2 will be skipped.

By following these best practices, you can write efficient, modular, and maintainable Ansible playbooks that can be easily adapted to different environments and situations.