What Is Ansible? Configuration Management Explained

Ansible is an agentless automation tool that configures servers and deploys software by running ordered tasks defined in YAML playbooks over SSH.

Ansible automates the repetitive work of configuring machines: installing packages, editing config files, starting services. It is agentless, connecting over SSH, and describes the desired configuration in readable YAML playbooks, making it approachable for both developers and operators.

What Ansible is

Ansible is an open-source automation tool for configuration management, application deployment, and orchestration. It connects to managed hosts over SSH (no agent required), and you describe what each host should look like in playbooks: ordered lists of tasks that call modules to enforce state.

Playbooks and idempotency

A playbook lists tasks, each invoking a module (install a package, copy a file, restart a service). Modules are designed to be idempotent: running a playbook twice leaves the system in the same state without redoing work that is already done. An inventory file lists the hosts and groups the playbook targets.

A playbook example

A task ensures a package is installed and a service running.

A minimal Ansible playbook

- hosts: web
  tasks:
    - name: Install nginx
      apt: { name: nginx, state: present }
    - name: Start nginx
      service: { name: nginx, state: started }

Role in CI/CD

In CI/CD, Ansible runs configuration and deployment steps: a pipeline can run a playbook to configure servers or roll out a new app version after a build passes. Running playbooks from CI gives consistency and an audit trail. Using "--check" mode in a pipeline previews changes without applying them, similar to a dry run.

Alternatives

Terraform provisions infrastructure (creating servers) while Ansible configures them, and the two are often used together. Chef and Puppet are agent-based configuration tools. Salt is another option. Ansible is favored for being agentless, simple to start with, and readable.

Key takeaways

Ansible configures servers agentlessly over SSH using YAML playbooks.
Modules are idempotent, so re-running converges to the same state.
In CI it runs configuration and deployment steps with an audit trail.