Creating Systemd Unit Files using Ansible

Posted by Ryan Himmelwright on Wed, Jul 29, 2020
Tags linux, systemd, customization, ansible
UNC-Chapel Hill Campus, Chapel Hill, NC

In my previous post, I created a systemd unit file to define an application as a service, and configured it to auto-start on my server. I’ve been making a big push to define the provisioning of all my homelab machines/VMs using automation. So the last step in setting up my FoundryVTT server, is to automate the process. Fortunately, creating a systemd unit file is quite easy to do using ansible.

Creating the Ansible Role

Let’s start by creating a role (if you don’t know what an ansible role is, checkout this guide I wrote not too long ago). First, create some directories:

cd roles
mkdir -p foundryvtt/{defaults,tasks,templates}

One difference from roles I’ve created previously, is that this one contains a templates directory. That is because this role will use a j2 template to define the systemd unit file, but more on that later.

Defining Variables

Lets create some files, starting with one to define the default variables. Open roles/foundryvtt/defaults/main.yaml and add the following:

---
user: "{{ ansible_user_id }}"
service_description: "A service to run the Foundry VTT node app"
foundryvtt_dir: "/home/{{ user }}/foundryvtt/"
foundrydata_dir: "/home/{{ user }}/foundrydata"

This defines a few default veriables that will be used in the service file template, as well as in the tasks file. The variables can optionally be over-ridden when running a playbook, but they will default to these values if not specified.

Making a Template

Now that the varibles are defined, we can create the unit file template. So, open a new file (roles/foundryvtt/templates/foundryvtt.service.j2 in my case), and insert the unit file from the previous post.

Next, walk through the file and substitute any values for the variables defined in the previous section:

[Unit]
Description={{ service_description }}
Documentation=https://foundryvtt.com
After=network.target

[Service]
Environment=NODE_PORT=30000
Type=simple
User={{ user }}
ExecStart=/usr/bin/node {{ foundry_dir }}/resources/app/main.js --dataPath={{ foundrydata_dir }}
Restart=on-failure

[Install]
WantedBy=multi-user.target

Great! This template is now ready to be used in our role.

Ansible Tasks

Last but not least, time to write some Ansible tasks. Open a new file (roles/foundryvtt/tasks/main.yaml), and lets start by adding any additional tasks this particular role needs, outside of the service file. For my example, this includes creating the defined data directories, unzipping the application source package, and opening required ports in the firewall:

## Note, you likely don't need these tasks. They are just for my particular
## example...
- name: Create foundryvtt dir at {{ foundryvtt_dir }}
  become_user: "{{ user }}"
  file:
    path: "{{ foundryvtt_dir }}"
    state: directory

- name: Create foundrydata dir at {{ foundrydata_dir }}
  become_user: "{{ user }}"
  file:
    path: "{{ foundrydata_dir }}"
    state: directory

- name: Send Foundry Package
  when: foundryvtt_send_src is defined and foundryvtt_send_src is not none
  copy:
    src: "{{ foundryvtt_send_src }}"
    dest: "{{ foundryvtt_package_src }}"

- name: Extract package
  unarchive:
    src: "{{ foundryvtt_package_src }}"
    dest: "{{ foundryvtt_dir }}"
    remote_src: yes

- name: Start firewalld
  systemd:
    name: firewalld
    state: started

- name: Open FoundryVTT Ports (firewalld)
  firewalld:
    port: 30000/tcp
    permanent: yes
    state: enabled

- name: reload service firewalld, in all cases
  systemd:
    name: firewalld
    state: reloaded

With all that defined, lets finally define a task to create our unit file using the template:

- name: Create foundryvtt systemd service file
  template:
    src: templates/foundryvtt.service.j2
    dest: /lib/systemd/system/foundryvtt.service

The src is set to the relative location (to the role) of the template we defined earlier, and the dest is set to where we would like the generated file to be copied to. This template is a unit file for a systemd service, so I’m going to copy it to /lib/systemd/system/foundryvtt.service.

Last but not least, lets start the newly created service:

- name: Start foundryvtt service
  systemd:
    name: foundryvtt
    state: started

… and… our role is finished!

Playbook

To run the role, it is easiest to have it run in a playbook. I try to define the provisioning of all my systems in their own playbooks, including my foundry server, so I use this role there. Just remember to call it in a roles: section of the playbook, like so:

  roles:
    - foundryvtt

Conclusion

That’s it. We’ve easily automated setting up the systemd unit file from the previous post using ansible. This makes defining and reproducing unit roles very simple. In addition, knowing how to use templates in ansible is very powerful, and I will definitely be utilizing them much more moving forward. Enjoy!

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