So the Ansible virt module doesn’t have a clone option and the creation of guests is a little limited. Because of this we have to use the shell or command modules and try to make them idempotent. This is a simple example and the dictionary can be expanded to a lot more customization. There is a way to use libvirt as a dynamic inventory and set group and host vars on guests, but I’ll cover that in a different post.

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Infrastructure testing provides some challenges just because of the mere fact you are building machines and not just compiling code. To test Ansible, I used to run Ansible with --syntax-check and --list-tasks. For roles I would run local tests with Vagrant using the tests/ directory in the role. The tests had Ansible test itself with the uri module or other checks. This is ok for simple checks but can be cumbersome and time consuming as it doesn’t catch everything.

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Ansible gives you conditionals to use when you want to check if something meets a certain criteria. However conditionals can become annoying if you need many include statements or repeat tasks based on facts. Here’s a way to minimize the need for them in the tasks themselves. Let’s take Apache for example: - name: install apache package: name: httpd state: installed when: ansible_distribution == 'CentOS' - name: install apache package: name: apache2 state: installed when: ansible_distribution == 'Ubuntu' This can become annoying and hard to read when it’s all in one file.

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One of Tower’s big selling points is the RESTful API. This allows systems to request certain templates to run against themselves from Tower. I leverage this on workstations with a systemd service and timer. Each workstation waits a predetermined time after boot and then does an API call to Tower. Tower then runs the workstation provision template against the system that requested it. To enable callbacks, just check “Allow Provisioning Callbacks.

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Author's picture

John Hooks

I do stuff with Linux.

Sr. System Engineer

Pittsburgh