playbook

I realized I've never posted this playbook to my blog... I needed to grab it for a project I'm working on, so I figured I'd post it here for future reference.

Basically, I need a playbook I can run whenever, that will ensure all packages are upgraded, then checks if a reboot is required, and if so, reboots the server. Afterwards, it removes any dependencies no longer required.

---
- hosts: all
  gather_facts: yes
  become: yes

  tasks:
    - name: Perform a dist-upgrade.
      ansible.builtin.apt:
        upgrade: dist
        update_cache: yes

    - name: Check if a reboot is required.
      ansible.builtin.stat:
        path: /var/run/reboot-required
        get_checksum: no
      register: reboot_required_file

    - name: Reboot the server (if required).
      ansible.builtin.reboot:
      when: reboot_required_file.stat.exists == true

    - name: Remove dependencies that are no longer required.
      ansible.builtin.apt:
        autoremove: yes

For a long time, I've had some Ansible playbooks—most notably ones that would install Docker then start some Docker containers—where I had to split them in two parts, or at least run them twice, because they relied on the control user having a new group assigned for some later tasks.

The problem is, Ansible would connect over SSH to a server, and use that connection for subsequent tasks. If you add a group to the user (e.g. docker), then keep running more tasks, that new group assignment won't be picked up until the SSH connection is reset (similar to how if you're logged in, you'd have to log out and log back in to see your new groups).

The easy fix for this? Add a reset_connection meta task in your play to force Ansible to drop its persistent SSH connection and reconnect to the server:

I've been working on some projects which require MFA for all access, including for CLI access and things like using kubectl with Amazon EKS. One super-annoying aspect of requiring MFA for CLI operations is that every day or so, you have to update your STS access token—and also for that token to work you have to update an AWS profile's Access Key ID and Secret Access Key.

I had a little bash function that would allow me to input a token code from my MFA device and it would spit out the values to put into my .aws/credentials file, but it was still tiring copying and pasting three values every single morning.

So I wrote a neat little executable Ansible playbook which does everything for me:

To use it, you can download the contents of that file to /usr/local/bin/aws-sts-token, make the file executable (chmod +x /usr/local/bin/aws-sts-token), and run the command:

Ubuntu 16.04 and 18.04 (and likely future versions) often don't have Python 2 installed by default. Sometimes Python 3 is installed, available at /usr/bin/python3, but for many minimal images I've used, there's no preinstalled Python at all.

Therefore, when you run Ansible playbooks against new VMs running Ubuntu, you might be greeted with the following error:

September 2018 Update: Ansible 2.7 (to be released around October 2018) will include a new reboot module, which makes reboots a heck of a lot simpler (whether managing Windows, Mac, or Linux!):

- name: Reboot the server and wait for it to come back up.
  reboot:

That's it! Much easier than the older technique I used in Ansible < 2.7!

One pattern I often need to implement in my Ansible playbooks is "configure-reboot-configure", where you change some setting that requires a reboot to take effect, and you have to wait for the reboot to take place before continuing on with the rest of the playbook run.

For example, on my Raspberry Pi Dramble project, before installing Docker and Kubernetes, I need to make sure the Raspberry Pi's /boot/cmdline.txt file contains a couple cgroup features so Kubernetes runs correctly. But after adding these options, I also have to reboot the Pi.