# Systemd Timers for Regular Tasks


## Create New Timer

To have custom executables run regularly on given time/interval, you may use the `base::timers` Hiera key:

```
base::timers:
    'timer_test':
        description: 'test timers'
        command: '/usr/bin/logger foo'
        on_calendar: '*:*:10'
        timer_options:
            persistence: false
        service_options:
            Environment: 'SOME_ENV=some_value'
            User: 'svcusr-logger'
        service_unit_options:
            OnSuccess: 'dnf-automatic'
            OnFailure: 'send-failure-email'
```

This then creates both the required timer and service unit files for systemd.

For each timer following keys are mandatory

- `description` for a short explanation what it is about
- `command` for the command to run
- `on_calendar` defining when it should run using the [`systemd` calendar event format](https://www.freedesktop.org/software/systemd/man/systemd.time.html#Calendar%20Events), (alternatively see also chapter "CALENDAR EVENTS" of `man systemd.date`)

Optional is

- `timer_options` for additional configuration in the `Timer` section of the timer unit. In the example it is `persistence` which signals if the timer should run immediately after boot when the node was switched of on the last scheduled run time (default is `false`).
- `service_options` for additional configuration in the `Service` section of the service unit.
- `service_unit_options` for additional options in the `Unit` section of the service unit.

## Enable/Disable Existing Timer
```
base::timers:
    'certbot':
        enable: true
```