Ansible — Infrastructure as Code without agents

Twenty servers, each configured differently. Documentation living inside one admin’s head. When they go on holiday, nobody knows how to set up a server. Infrastructure as Code with Ansible changed that — servers are defined in YAML, versioned in git.

Why Ansible¶

Agentless: Ansible communicates over SSH. No agent on the servers, no daemon, no additional infrastructure. Puppet and Chef require an agent — more software to maintain. YAML: Playbooks in readable YAML. No Ruby (Chef) or DSL (Puppet).

Playbook example¶

---
- hosts: webservers
  become: yes
  tasks:
    - name: Install Nginx
      apt: name=nginx state=latest
    - name: Deploy config
      template: src=nginx.conf.j2 dest=/etc/nginx/nginx.conf
      notify: Restart Nginx
    - name: Ensure running
      service: name=nginx state=started enabled=yes
  handlers:
    - name: Restart Nginx
      service: name=nginx state=restarted

Idempotence and roles¶

Every task is idempotent — run the playbook 10 times and the result is the same. Roles organise logic into reusable packages: role nginx, role postgresql, role java. Ansible Galaxy for sharing community roles.

Inventory and dynamic inventory¶

Static inventory for fixed servers. For cloud environments, a dynamic inventory script that queries the AWS/Azure API and returns the current list of servers.

Servers as code¶

Ansible is the most accessible path to Infrastructure as Code. Agentless, YAML, SSH. Server documentation lives in git; onboarding means reading the playbook.