What is Ansible?

Introduction

Ansible is an open-source automation tool used for IT tasks such as configuration management, application deployment, and orchestration. It was created by Michael DeHaan in 2012, and since then it has become a popular choice among DevOps engineers and system administrators.

In this article, we will cover the basics of Ansible and provide some examples to help you get started.

What is Ansible?

Ansible is a configuration management tool that allows users to automate repetitive tasks. It uses a simple, easy-to-learn language called YAML (yet another markup language or recursively YAML Ain't Markup Language) to describe configurations and tasks. Ansible doesn't require any agents or daemons on the managed nodes, which makes it lightweight and easy to use.

Ansible Architecture

The Ansible architecture consists of the following components:

1. Control Node: This is the machine from which Ansible is run. It contains the Ansible installation and the inventory of managed nodes.
2. Managed Nodes: These are the machines that Ansible manages. Ansible can manage a wide range of machines, including physical servers, virtual machines, and cloud instances.
3. Inventory: This is a list of managed nodes that Ansible can control. It can be a simple text file or a dynamic inventory that pulls information from a cloud provider.
4. Playbooks: Playbooks are Ansible's configuration files that describe the desired state of the managed nodes. They contain a set of tasks that Ansible executes on the managed nodes.
5. Modules: Modules are pre-built scripts that Ansible uses to perform specific tasks on the managed nodes. Ansible comes with a large library of modules that cover a wide range of tasks.

Examples

Now, let's look at some examples of how to use Ansible.

1. Installing Packages

One of the most common tasks in system administration is installing software packages. With Ansible, you can install packages on multiple nodes simultaneously.

To install a package, you need to create a playbook that specifies the package name and the nodes on which it should be installed. Here's an example playbook that installs the Apache web server on two nodes:

---

- name: Install Apache on CentOS

  hosts: web

  become: true

  tasks:

  - name: Install Apache

    yum:

      name: httpd

      state: present

 

In this playbook, we specify the name of the package to install (httpd) and the state (present) to ensure that the package is installed.

2. Managing Services

Once you've installed a package, you need to start and manage the associated service. Ansible can help you do that too.

Here's an example playbook that starts the Apache web server and ensures that it starts automatically on boot:

---

- name: Start Apache on CentOS

  hosts: web

  become: true

  tasks:

  - name: Start Apache

    service:

      name: httpd

      state: started

      enabled: true

 

In this playbook, we use the service module to start the Apache service and set it to start automatically on boot (enabled: true).

3. Copying Files

Copying files between machines is another common task in system administration. Ansible makes it easy to copy files between nodes.

Here's an example playbook that copies a file from the control node to a managed node:

---

- name: Copy file to CentOS

  hosts: web

  become: true

  tasks:

  - name: Copy file

    copy:

      src: /path/to/local/file

      dest: /path/to/remote/file

 

In this playbook, we use the copy module to copy a file from the control node to a managed node. We specify the source file (/path/to/local/file) and the destination file (/path/to/remote/file).

4. Managing Users

Managing user accounts is another task that Ansible can handle. You can create and delete user accounts, set passwords, and manage SSH keys.

Here's an example playbook that creates a new user account and adds an SSH key:

 

---

- name: Create user on CentOS

  hosts: web

  become: true

  tasks:

  - name: Create user

    user:

      name: john

      password: "{{ 'password' | password_hash('sha512') }}"

  - name: Add SSH key

    authorized_key:

      user: john

      key: "{{ lookup('file', '/path/to/public/key') }}"

 

In this playbook, we use the user module to create a new user account (name: john) and set the password using the password_hash filter. We then use the authorized_key module to add an SSH key to the user's authorized_keys file.

 

5.      Sample inventory, yaml and ansible playbook command for installing Apache on 2 servers

 

First, we need to create an inventory file that lists the servers we want to manage:

[web-servers]

server1

server2

 

Here we created a group called "web-servers" and added server1 and server2 to it.

2.      Next, we create a playbook file that will describe the tasks we want to perform on the servers. Let's call it apache.yml:

---

- name: Install Apache

  hosts: web-servers

  become: true

  tasks:

    - name: Install Apache

      yum:

        name: httpd

        state: latest

    - name: Start Apache

      service:

        name: httpd

        state: started

 

This playbook will:

•       Install the latest version of Apache using the yum package manager.
•         Start the Apache service using the service module.

 

3.      Finally, we can run the playbook using the ansible-playbook command:

ansible-playbook apache.yml

This will connect to each server in the web-servers group, and execute the tasks specified in the playbook.

PLAY [Install Apache] *****************************************************************

 

TASK [Gathering Facts] ****************************************************************

ok: [server1]

ok: [server2]

 

TASK [Install Apache] ******************************************************************

changed: [server1]

changed: [server2]

 

TASK [Start Apache] ********************************************************************

changed: [server1]

changed: [server2]

 

PLAY RECAP ****************************************************************************

server1                    : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

server2                    : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

conclusion

Ansible is a powerful automation tool that can help you streamline your IT tasks. It is easy to learn and use, and it doesn't require any agents or daemons on the managed nodes. With Ansible, you can automate tasks like installing software packages, managing services, copying files, and managing user accounts. These examples are just the tip of the iceberg – Ansible can handle a wide range of tasks and scenarios. If you're looking to streamline your IT operations, Ansible is definitely worth considering.