Ansible: A Primer, Installation, and Deploying 500 Docker Containers

Ansible is an open-source automation tool, used for configuration management, application deployment, and task automation. Unlike other management tools, Ansible uses an agentless architecture, relying on SSH to push changes from a single source to remote servers. This makes it less intrusive and easier to adopt. One notable use case for Ansible is to deploy Docker containers across multiple hosts. In this article, we’ll dive into Ansible’s usage, installation, and how you can deploy 500 Docker containers using an Ansible playbook.

Installation

Installing Ansible is straightforward:

On Ubuntu/Debian:

sudo apt update
sudo apt install -y ansible

On CentOS/RHEL:

sudo yum install -y ansible

Ansible Basics

Ansible uses “playbooks” written in YAML format to describe automation tasks. These playbooks define a set of activities and are designed to be human-readable.

A basic structure of an Ansible playbook includes:

• hosts: Specifies the remote machines where tasks should run.
• tasks: Lists the tasks to be executed.

Deploying 500 Docker Containers using Ansible

1. Setting Up Docker:Before deploying Docker containers, ensure Docker is installed on the target hosts. You can use Ansible itself to automate the Docker installation.
2. Writing the Playbook:Create a playbook, say deploy-docker.yml, with the following content:

---
- hosts: your_target_group
  tasks:
  - name: Install Docker
    command: curl -sSL https://get.docker.com/ | sh
    
  - name: Start Docker service
    service:
      name: docker
      state: started
      
  - name: Deploy 500 Docker containers
    command: docker run -d your_docker_image
    with_sequence: count=500

1. Replace your_target_group with the group of hosts you intend to deploy Docker containers on, and your_docker_image with the image you wish to run.
2. Run the Playbook:Execute the playbook using

ansible-playbook -i your_inventory_file deploy-docker.yml

Replace your_inventory_file with the path to your Ansible inventory, which lists the addresses of your target machines.

Conclusion

Ansible provides a robust, agentless approach to automation that is versatile and scalable. Whether you’re managing configurations, deploying applications, or orchestrating Docker containers across a vast fleet of servers, Ansible offers an intuitive solution. Deploying 500 Docker containers, as illustrated, is just one demonstration of its power. As you delve deeper into Ansible’s capabilities, you’ll discover a wide array of modules and playbooks available to streamline your infrastructure management and application deployment tasks.