Ansible Reboot Only If Required

Mar 9, 2021 linux misc-web
This post is more than 18 months old. Since technology changes too rapidly, this content may be out of date (but that's not always the case). Please remember to verify any technical or programming information with the current release.

This quick tip will help you issue a reboot command during your Ansible playbook if a reboot is required.

This has only been tested on Ansible 2.9.13 for a debian-based host system.

For my scenario, I wanted to do a complete dist upgrade as the first thing for this virtual machine (I normally would recommend against this much of a drastic upgrade, but this is for a throw-away implementation).

After the upgrade, a lot of times a reboot is required. Luckily Ansible has the reboot method built in. Now, all you have to do is check if a reboot is required. (The best thing about this method is that Ansible is in control of the reboot so it won’t just timeout future commands).

Let’s take a look at some tasks with this implemented:

- name: Update apt-cache and do dist upgrade
    update_cache: yes
    cache_valid_time: 3600
    upgrade: dist

- name: Check if reboot required
    path: /var/run/reboot-required
  register: reboot_required_file

- name: Reboot if required
  when: reboot_required_file.stat.exists == true
- name: Install snapd
    name: snapd
    state: present

The first step is to update apt-cache and do a dist upgrade. Then, ansible will register if the /var/run/reboot-required file exists. (This is also what motd uses I think to tell you a reboot is required.) Then, if that stats true, reboot is called. After that, we continue with our playbook. In my example, installing snapd.

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