Ansible

Ansible is a tool used for managing infrastructure. For example, if you have a number of machines in your test system, you might manage updates etc. on all of them with ansible.

Ansible uses control nodes, which can be any machine with ansible installed, to send commands and instructions to managed nodes.

Ansible uses SSH and SFTP/SCP, so no agent needs to be added to the managed nodes. This makes it handy for tasks such as provisioning.

Getting Started

To get started you will need one machine with ansible installed, and one which will act as the managed node. To setup the managed node, you need to install an ssh client on it and add the control machine’s public ssh key to the authorized keys file.

You can then produce an ansible inventory file:

Example of an ansible inventory file called β€œhosts”
host1 ansible_host=172.17.0.2 ansible_user=user ansible_ssh_private_key_file=~/.ssh/id_rsa

You can then run a simple ping test on all hosts specified in the hosts file with:

This is an example of an β€œad-hoc” command.

Playbooks

This is a way for ansible to automate repeating tasks. This is done using structured files written in yaml as an ordered set of steps to run.

You can run this using a command like:

Using Variables

You can add variables in your playbook yaml files.

Note when assigning a variable to another, you have to use the double quotes.

You can also add arguments via the command line: e.g.

Modules

Modules are discrete units of code that can be used from command line or in a playbook task. Ansible ships with a load of readily available modules.

Note

Use the command ansible-doc -l to list all modules. Or for documentation on a single module, use ansible-doc <module>.

It is possible to enable a custom module by adding it to one of these locations:

  1. Add path to ANSIBLE_LIBRARY

  2. ~/.ansible/plugins/modules/

  3. /usr/share/ansible/plugins/modules/

Follow this link for an example of creating your own module:

https://docs.ansible.com/ansible/latest/dev_guide/developing_modules_general.html#creating-a-module