View source for XELK-AN-008: How to use systemd on an Embedded system

==== Specific sections ====

Some ''Unit'' have specific sections based on their characteristic. The most important is the section '''Service''' related to the Unit <code>.service</code>

Please find more information at the [https://www.freedesktop.org/software/systemd/man/systemd.service.html# documentation page]

===== [Service] section =====

Used for providing configurations for the ''services''.

====== Type ======

<code>Type=</code> uses one of the (main) following values:

{| class="wikitable"
|-
! Value !! Description
|-
| simple || Default configuration for a service when specified <code>ExecStarts=</code>
|-
| forking || the process will call a <code>fork()</code> when starts causing the father to exit. This informs systemd that the process is still alive even if the father has been terminated.
|-
| oneshot: || the process has a very short execution time and then systemd should wait for its termination before continuing with other Units. this is the default configuration if <code>ExecStarts=</code> is not specified.
|-
| dbus || the Unit will acquire the name on the D-Bus. systemd will continue to process the other Units
|-
| notify || the service will notify when completely initialized. systemd will wait for the notification before continuing with the following Units
|-
| idle || the service will not be executed until all active jobs are dispatched.
|}

====== Other options ======

{| class="wikitable"
|-
! Value !! Description
|-
| ExecStarts=: || Specifiy the full path and parameters for executing a service. If preceded by a "-" this inform that the command failure can be accepted.
|-
| ExecStartsPre=: || used for adding more commands to be executed before starting the main process. May be used multiple times specifying the complete path and command parameters.
|-
| ExecReload=: || commands to be executed for reloading the service configuration.
|-
| ExecStop=: || commands required for stopping the service. If missing, the service will be killed.
|-
| ExecStopPost=: || commands to be executed after the service has been stopped..
|-
| RestartSec=: || time to sleep (seconds) before restarting the service.
|-
| Restart=: || restart conditions for systemd to be checked before restarting the service (if terminated). Can be set to "always","on-success", "on-failure", "on-abnormal", "on-abort", or "on-watchdog". 
|-
| TimeoutSec=: || time to sleep during ''start'' or ''stop'' before considering the process failed on start or stop. Start and stop timeout can be set with different values using <code>TimeoutStartSec=</code> and <code>TimeoutStopSec=</code>
|}