How to deploy Docker on a server using Ansible

Are you looking to streamline your deployment processes and embrace automation for managing Docker environments? With Docker becoming a staple in modern application deployment and Ansible providing powerful orchestration capabilities, integrating these tools can revolutionize your workflow. In this guide, we will delve into how to deploy Docker on a server using Ansible, ensuring a repeatable and efficient process suitable for both development and production environments.

Understanding Docker and Ansible

Docker is a platform that allows developers to automate the deployment of applications inside lightweight containers, making them portable across different environments. Ansible, on the other hand, is a configuration management tool that automates software provisioning, configuration management, and application deployment using simple YAML files in a declarative manner. This synergy enables Infrastructure as Code (IaC), which is pivotal for modern DevOps practices.

Prerequisites

Before we dive into the steps, ensure the following prerequisites are met:

1. An Ubuntu server (16.04 or later) with SSH access.
2. Ansible installed (preferably version 2.9 or later).
3. You have root or sudo privileges on the server.

To install Ansible, run:

sudo apt update
sudo apt install ansible -y

Step 1: Preparing the Ansible Inventory

Ansible needs to know which server it needs to manage. This is done using an inventory file. Create or edit your inventory file, usually located at /etc/ansible/hosts:

[my_servers]
192.168.1.100 ansible_ssh_user=your_username

Replace 192.168.1.100 with your server's IP address.

Step 2: Writing the Ansible Playbook

Create a new playbook file in your working directory. Name it deploy_docker.yml:

---
- hosts: my_servers
  become: yes
  tasks:
    - name: Update apt repository and install prerequisites
      apt:
        update_cache: yes
        name:
          - apt-transport-https
          - ca-certificates
          - curl
          - software-properties-common
        state: present

    - name: Add Docker GPG key
      apt_key:
        url: "https://download.docker.com/linux/ubuntu/gpg"
        state: present

    - name: Add Docker repository
      apt_repository:
        repo: "deb [arch=amd64] https://download.docker.com/linux/ubuntu {{ ansible_distribution_release }} stable"
        state: present

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

    - name: Start Docker service
      service:
        name: docker
        state: started
        enabled: yes

This playbook includes tasks to prepare the server, install Docker, and ensure the Docker service is running.

Step 3: Running the Ansible Playbook

Execute the playbook using the following Ansible command:

ansible-playbook -i /etc/ansible/hosts deploy_docker.yml

Expected Output:

PLAY [my_servers] *********************************************

TASK [Update apt repository and install prerequisites] ********
... ok

TASK [Add Docker GPG key] ***************************************
... ok

TASK [Add Docker repository] *************************************
... ok

TASK [Install Docker] ********************************************
... changed: [192.168.1.100]

TASK [Start Docker service] ***************************************
... ok

PLAY RECAP ****************************************************
192.168.1.100             : ok=5    changed=1    unreachable=0    failed=0    skipped=0   

Check for errors in the output to troubleshoot if necessary. Common issues include network connectivity or permissions problems.

Troubleshooting Common Issues

• Key error: If you encounter issues regarding the GPG key, ensure that the URL in the apt_key module is correct and accessible from your server.
• Failed to start Docker: Use sudo systemctl status docker to diagnose issues. The logs typically provide insight into the problem.

Conclusion

By automating Docker installation with Ansible, you not only increase efficiency in your deployment process but also enhance repeatability and consistency, which are key aspects of modern application deployment strategies. Embrace IaC tools to simplify complex tasks and ensure your environments are always up to date. This method sets a strong foundation for future automation that can extend to deploying, managing, and scaling containerized applications.