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Application Deployment on Instances

Ansible, an open-source automation tool, helps reduce complexity and supports versatile tasks. Using Ansible allows automating nearly any operation.

Deploying an Application on an Instance​

Requirements:​

  • One Ansible Control Node
  • One or more Ansible Managed Nodes
  • Ensure all nodes use the same SSH_KEY
  • Verify the Ansible Control Node is set up to manage the Ansible Hosts over SSH.
  • Operating System: Ubuntu 22.04

Step 1: Update and Upgrade All Nodes​

Run the following command on all nodes:

sudo apt-get update -y && sudo apt-get upgrade -y

Step 2: Establish SSH Connection Between Nodes​

On the Control Node, navigate to the .ssh directory:

cd ~/.ssh/

Create a file named ansible_key:

vi ansible_key

Paste the key you downloaded during server creation into the file.

Secure the key by modifying file permissions:

chmod 700 ~/.ssh/  
chmod 600 ~/.ssh/ansible_key

Test the SSH connection from the Control Node to the Managed Nodes.

Installing Ansible on the Control Node​

To manage infrastructure with Ansible, the software must be installed on the Control Node.

Step 3: Add the Official Ansible PPA​

sudo apt-add-repository ppa:ansible/ansible

Step 4: Refresh the Repository​

sudo apt-get update -y

Step 5: Install Ansible​

sudo apt-get install ansible -y

Creating an Ansible Inventory File​

The Inventory File lists the hosts managed by Ansible. Choose between INI and YAML formats.

INI Format Example:​

[webservers]
webserver1.example.com
webserver2.example.com

[dbservers]
dbserver.example.com

YAML Format Example:​

children:  
  webservers:  
    hosts:  
      webserver1.example.com:  
      webserver2.example.com:  
  dbservers:  
    hosts:  
      dbserver.example.com:

To create an inventory file, use the following command:

vi /etc/ansible/hosts

Add the following content:

[servers]
server1 ansible_host=<Host-1_IP>
server2 ansible_host=<Host-2_IP>

[all:vars]
ansible_python_interpreter=/usr/bin/python3

Validate the Inventory File​

Use this command to check the file:

ansible-inventory --list -y -i /etc/ansible/hosts

Testing Connections Between Nodes​

To ensure successful connectivity, use the ping module:

ansible all -m ping -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Check available storage:

ansible all -a "free -h" -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Check server uptime:

ansible servers -a "uptime" -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Writing and Executing Playbooks​

A playbook is where you define automated tasks. Use a YAML file for your playbooks.

Example: Creating a File on All Nodes​

Navigate to the playbook directory:

sudo mkdir -p /etc/ansible/playbook/  
cd /etc/ansible/playbook/  
vi create_file.yml

Add the following content:

name: This playbook creates a file
hosts: all
become: true
tasks:
    name: Create a file
    file:
      path: /home/ubuntu/server_file.txt
      state: touch

Run the playbook:

ansible-playbook create_file.yml -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Adding a User to All Servers​

Create a playbook to add a user:

vi playbook_user.yml

Insert the following content:

name: This playbook creates a user
hosts: all
become: true
tasks:
  - name: Create a user named testing_user
    user:name = server_testing_user

Run the playbook:

ansible-playbook playbook_user.yml -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Installing Docker via Ansible​

To deploy Docker, follow these steps:

  1. Prepare the Inventory File (already created).
  2. Install the Docker Role.
  3. Write a Playbook.
  4. Execute the Playbook.

Docker installation requires adding GPG keys and repositories, which can be included in the playbook.

Example: Docker Installation Playbook​

Navigate to the playbook directory:

cd /etc/ansible/playbook/  
vi docker_install.yml

Add content to install Docker:

Run the playbook:

ansible-playbook docker_install.yml -i /etc/ansible/hosts --private-key=~/.ssh/ansible_key

Verify Docker installation on nodes:

docker -v

By following this procedure, Docker will be successfully installed across all nodes managed by Ansible, ensuring uniform environments.