Configure Linux-based web and database servers using Ansible playbooks 📚

Configuration Management Tools ⚒

• Configuration management tools are idempotent
• They save the state of the target machines
• They always check if the target is already in the same state as the new state
• They will compare the state of the configuration
• They apply configuration changes only if a difference exists
• But scripts rerun the tasks unless some intelligence is applied to it

Setup 💻

1. Login to your AWS account
2. Create a Ubuntu-based EC2 instance and install Ansible on it
3. Create a key pair for this control machine
4. Create 2 more instances, both CentOS with one as a web server and another as a database server
5. Create a key pair for these instances which will help to ssh into the instance
6. Download both of the key pairs
7. ssh into the control machine and copy the key pair for target machines from the local device to the control machine

Use cases of Ansible

1. Automation - any system automation
2. Change management - prod server changes
3. Provisioning - setup physical/cloud servers
4. Orchestration - large-scale automation framework

Note: Here, we will be using Ansible for change management.

Hands-on part... 👐

Let's begin by looking at the files in the working directory

• The client-key.pem file is the key used to ssh into the target machines from the control machine
• There is an inventory file which contains a list of all the target machines
• There are 3 playbooks, one for the web server, one for the database server, and one with configuration for both
• There is a folder which has index.html file to be deployed on the web server

Aim

• Deploy the index.html file on the web server (using the web-target.yaml file)
• Create a new database and a new user on the database server (using the db-target.yaml file)

Ansible playbooks

• A playbook is like a YAML configuration file
• Each playbook contains multiple plays
• Each play contains tasks that will be executed
• These tasks are executed on the target machine

Inventory file

all:
  hosts:
    web01:
      ansible_host: 172.31.81.92
    web02:
      ansible_host: 172.31.94.211
    db01:
      ansible_host: 172.31.81.236

  children:
    webservers:
      hosts:
        web01:
        web02:
    dbservers:
      hosts:
        db01:
      vars:
        ansible_user: ec2-user
        ansible_ssh_private_key_file: client-key.pem

Explanation

Commands to execute 🔢

• Login into the control machine which has the key for the target machines

• Execute the following commands...

  1.

   ansible playbook -i inventory target.yaml
  

Output

• httpd service is installed and started on the web target machine
• maria-db service is installed on the database machine

2.

ansible playbook -i inventory target.yaml

Output

• maria-db service is started and enabled on the database machine

3.

ansible playbook -i inventory web-target.yaml

Output

• The index.html file is pushed to the web target machine

• The output is available on IP_address:80 of the web server

  

  

4.

ansible playbook -i inventory db-target.yaml

Output

• A database is created with the name accounts
• A user is created with the name my_user

Note 📝

Notice same commands repeated in target.yaml and both the separate target files?

The repeated commands in db-target.yaml and web-target.yaml, despite being present in target.yaml, provide modularity and flexibility.

• target.yaml: Sets up both the web and database servers in a single run (initial setup or large changes).
• db-target.yaml and web-target.yaml: Allow focused updates or maintenance on just the web server or the database server without affecting the other.