wiki/notebook/linux.systemd.unit-templates.org

:PROPERTIES:
:ID:       14b49597-011c-4da1-b955-bed6059af4a3
:END:
#+title: systemd unit templates
#+date: 2021-08-07 19:55:05 +08:00
#+date_modified: 2021-08-07 19:55:26 +08:00
#+language: en


You can create unit templates which is useful for simple services that only requires an argument.
Rather than creating individual simple service files, let systemd handle it.

For example, you may want to spawn a service for Borgmatic with multiple repos.
If you don't know templates, the dumb way to serve multiple repos is to create individual unit files for each.
If you want to schedule them, you also have to create a timer unit for each.

The more efficient solution is to use templates.
To make a unit template, there are only a handful of requirements:

- Addition of =%i= to represent the template value.
- The unit file name has to end with =@= (e.g., =unit-name@.service=, =unit-name@.timer=).

This could be compressed into a template for a service unit.
The following code shows how to create one.

#+begin_src ini
[Unit]
Description=Periodic safety backup for %i
Documentation=man:borg(1) https://www.borgbackup.org/

[Service]
Type=simple
ExecStart=borgmatic --config %i --verbose

[Install]
WantedBy=default.target
#+end_src

To use the service, you have to give it a value — e.g., ~systemctl --user start borg-backup@test.yaml.service~.

That's all good but what about scheduling them?
What if you want to create an archive every hour starting at 08:00?
You can just create a templated timer unit.

#+begin_src ini
[Unit]
Description=Periodic safety backup for %i
Documentation=man:borg(1) https://www.borgbackup.org/

[Timer]
Unit=borg-backup@%i.service
Calendar=08/1:00:00
Persistent=true

[Install]
WantedBy=default.target
#+end_src