Step-by-Step Guide: Using Ansible with Docker

In the ever-evolving landscape of DevOps, efficient automation and containerization have become essential components of modern IT infrastructure. Ansible and Docker are two powerful tools that, when combined, can streamline deployment processes and enhance overall system manageability. This step-by-step guide will walk you through the process of using Ansible with Docker, demonstrating how to leverage these tools for seamless integration and deployment.

1. Setting Up Your Environment:
   Before diving into Ansible and Docker integration, ensure both tools are installed on your system. Use the following commands to install Ansible and Docker:

   # Install Ansible
   sudo apt update
   sudo apt install ansible
   
   # Install Docker
   sudo apt install docker.io
   

2. Configuring Ansible for Docker:
   Create an Ansible inventory file to define the hosts and connection parameters. This file typically resides at /etc/ansible/hosts. Add the IP addresses of your Docker hosts and specify the connection type:

   [docker_hosts]
   192.168.1.1 ansible_connection=ssh ansible_ssh_user=user
   

3. Creating Ansible Playbooks:
   Ansible playbooks are YAML files that define a set of tasks to be executed on remote hosts. Create a playbook for Docker-related tasks, such as installing Docker, managing containers, and handling images. Here's a simple example:

   # docker_setup.yaml
   ---
   - name: Install Docker
     hosts: docker_hosts
     tasks:
       - name: Install Docker
         apt:
           name: docker.io
           state: present
   

4. Executing Ansible Playbooks:
   Run your Ansible playbook using the following command:

   ansible-playbook docker_setup.yaml
   

   Ansible will connect to the specified hosts and execute the defined tasks, ensuring Docker is installed and ready for use.

5. Managing Docker Containers:
   Ansible allows you to manage Docker containers effortlessly. Create a playbook to deploy and manage a sample container:

   # deploy_container.yaml
   ---
   - name: Deploy Docker Container
     hosts: docker_hosts
     tasks:
       - name: Pull Docker Image
         docker_image:
           name: nginx
           source: pull
   
       - name: Run Docker Container
         docker_container:
           name: my_nginx
           image: nginx
           state: started
           ports:
             - "80:80"
   

6. Executing Docker Playbooks:
   Run the Docker playbook similarly to the previous one:

   ansible-playbook deploy_container.yaml
   

   This playbook will pull the official Nginx image and deploy a container named "my_nginx" on the specified hosts.

7. Scaling with Docker Compose:
   Extend your Ansible playbook to use Docker Compose for orchestrating multi-container applications. Define a docker-compose.yaml file and incorporate it into your playbook.

   # docker_compose.yaml
   version: '3'
   services:
     web:
       image: nginx
       ports:
         - "8080:80"
   

   Modify the Ansible playbook:

   # deploy_compose.yaml
   ---
   - name: Deploy Docker Compose
     hosts: docker_hosts
     tasks:
       - name: Install Docker Compose
         apt:
           name: docker-compose
           state: present
   
       - name: Deploy Docker Compose
         command: docker-compose up -d
         args:
           chdir: /path/to/compose/file
   

8. Running the Docker Compose Playbook:
   Execute the Docker Compose playbook:

   ansible-playbook deploy_compose.yaml
   

   This will install Docker Compose and deploy the multi-container application defined in the docker-compose.yaml file.

Combining Ansible with Docker provides a powerful automation solution for managing and deploying containerized applications. By following this step-by-step guide, you've learned the basics of setting up the environment, creating Ansible playbooks, managing Docker containers, and scaling applications using Docker Compose. Feel free to explore further and adapt these examples to suit your specific requirements.