Ansible

Source: What is Ansible | Ansible Playbook explained | Ansible Tutorial for Beginners - YouTube

What is Ansible

Introduction to Ansible

Tool to automate IT tasks

Open source GPL licensed

Why automate?

Save time, reduce errors, ensure consistency

Solve repetitive and distributed tasks:
- Updates, backups, system reboots, user management
- Manage multiple, distributed systemsm complex systems
For example, update Docker on 10 machines
Naive approach: Document through notes, then manually execute

When is Ansible Used? Use Cases

4 different ways Ansible helps:
- Execute task from one machine
- Config steps with YAML file(s)
- Re-use same YAML files for different environments
- Efficient, reliable and less errors

Ansible supports all infrastructure:

Operating systems, cloud, on-prem
- Integrations vendor supported
Agentless, managed remotely from one machine - advantages:
- No deployment or upgrade effort

Ansible Components

Modules and Playbooks

Modules:

Small programs that do the work. They are sent to the target server. One specific tasks like:
- Start docker container
- Create/copy file
- Start nginx service

There are modules to work with many systems, some examples:

Cloud
Commands
Database
Files
Network
Security
Source control
System

Simple to Understand becase of use of YAML

Ansible uses YAML, making it easier to understand and human readable.

Usage, Playbooks

Because modules do specific things, multiple modules will be required for complex tasks.
Sequential modules are grouped into tasks. For example:
- Task: rename table, set owner of table, and truncase table.
- Task: create directory, install nginx, start nginx

Tasks Configuration
- Hosts: where to run
- Vars: variables
- remote_user: user to run as
- Module name: what to run
- Arguments: what to do
Indentation is used in YAML to show hierarchy and is strict.

Plays and Playbooks

Play = combination of above: hosts, vars, remote_user, tasks with modules and arguments. Should be named after the sequential tasks

Playbook = 1 or more plays

How and in which order
At what time and where (which hosts)
What modules should be executed

Example Playbook:

hosts: webservers
remote_user: root

# Play for Webservers
tasks:
    - name: create directory for nginx
      file:
        path: /etc/nginx
        state: directory
    - name: install nginx latest version
      apt:
        name: nginx
        state: latest
    - name: start nginx
        service:
            name: nginx
            state: started

# Play for Database
- hosts: databases
  remote_user: root

  tasks:
        - name: rename table
        mysql_db:
            name: old_table
            rename: new_table
        - name: set owner of table
        mysql_user:
            name: new_table
            priv: '*.*:ALL'
        - name: truncate table
        mysql_db:
            name: new_table
            state: import
            target: /tmp/new_table.sql

Host Definition

Set in Hosts File or Inventory = all machines involed in task executions
- Includes IPs or hostnames
- Can be grouped like webservers, databases
- Can be any type of server (cloud, virtual, bare metal)
For example:
```
10.24.0.100

[webservers]
10.24.0.1
web1.myserver.com

[databases]
10.24.1.4
db1.myserver.com
```

Ansible with Docker and Other Environments

Dockerfile to prepare application environment, for example config file, set log directory, env varaibles, app.jar, start script

Using Ansible, use the same configuration for the Docker container, but use it also on:

Docker / Vagrant container
Cloud instance
Bare metal

Ansible allows to reproduce the application in any environment

Ansible can also manage the container on the host level, for example with storage and network.

Ansible Tower

UI Dashboard from Redhat to centrally store and manage tasks, collaborate with other, manage inventories

Alternatives to Ansible like Puppet and Chef

Ansible	Puppet and Chef	Comment
YAML	Ruby	YAML is easier to learn
Agentless	Agent based, installation	Less deployment required