Linux 117: Automating with Ansible for Configuration Management

Linux 117: Automating with Ansible for Configuration Management

As your infrastructure grows, manually configuring and maintaining each server becomes inefficient and error-prone. Ansible is a powerful automation tool that simplifies configuration management, application deployment, and task execution across multiple Linux systems — all without installing agents.

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1. What is Ansible?

Ansible is an open-source automation platform that allows you to manage servers via SSH using simple, human-readable YAML files called playbooks.

• Agentless: No software required on managed hosts.
• Idempotent: Ensures the same result every time.
• Easy to Learn: Uses plain English in YAML format.

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2. Installing Ansible

On Debian/Ubuntu

sudo apt update
sudo apt install ansible

On RHEL/CentOS/Fedora

sudo dnf install epel-release
sudo dnf install ansible

Verify installation:

ansible --version

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3. Setting Up an Inventory

The inventory file lists the hosts Ansible will manage.

Example: /etc/ansible/hosts

[webservers]
192.168.1.10
192.168.1.11

[dbservers]
192.168.1.20

You can also use dynamic inventory scripts or tools like Ansible Tower for large environments.

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4. Connecting with SSH

Ansible uses SSH for communication. Ensure you can connect to the managed hosts with SSH keys:

ssh-copy-id user@192.168.1.10

Test connection:

ansible all -m ping -u user

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5. Running Your First Ansible Command

Use ad-hoc commands to quickly execute tasks:

ansible webservers -m apt -a "name=nginx state=present" -b -u user

• -m: Module (e.g., apt, yum, copy, service)
• -a: Arguments
• -b: Become (sudo)
• -u: User

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6. Creating and Running a Playbook

A playbook defines multiple tasks to run in sequence.

Example: install_nginx.yml

---
- name: Install and Start NGINX
  hosts: webservers
  become: yes

  tasks:
    - name: Install NGINX
      apt:
        name: nginx
        state: present

    - name: Start NGINX
      service:
        name: nginx
        state: started
        enabled: yes

Run the playbook:

ansible-playbook install_nginx.yml -u user

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7. Variables and Templates

Use variables to customize tasks:

vars:
  nginx_port: 8080

Use Jinja2 templates (.j2) to configure dynamic files:

Example: nginx.conf.j2

server {
    listen {{ nginx_port }};
    server_name localhost;
    root /var/www/html;
}

Use the template module to apply it.

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8. Ansible Roles for Reusability

Roles help organize your playbooks by separating code into reusable components:

roles/
├── nginx/
│   ├── tasks/
│   ├── handlers/
│   ├── templates/
│   └── defaults/

Use roles in playbooks:

roles:
  - nginx

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9. Managing Secrets with Ansible Vault

Encrypt sensitive data like passwords and keys:

ansible-vault create secrets.yml

Edit:

ansible-vault edit secrets.yml

Use in playbooks:

vars_files:
  - secrets.yml

Run with decryption:

ansible-playbook playbook.yml --ask-vault-pass

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10. Conclusion

Ansible transforms Linux server management from tedious manual tasks to reliable, repeatable automation. With just a few commands or YAML files, you can provision entire environments quickly and consistently.

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Next Steps:

• Learn Ansible Galaxy for reusable community roles
• Explore Ansible AWX/Tower for a web UI and job scheduling
• Automate more complex workflows like multi-node deployments

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Coming next: Linux 118: Systemd Deep Dive – Managing Services and Boot Processes