====== shutdown ======

===== reduce reboot/shutdown timeout =====

<code bash>
systemctl edit reboot.target
systemctl edit soft-reboot.target
systemctl edit ctrl-alt-del.target
systemctl edit poweroff.target
</code>

and change
<code ini>
[Unit]
JobTimeoutSec=30min 
</code>

or use unit override files.


===== run service at shutdown =====

==== run service very late  ====

**Drawbacks:**
If service is scheduled before shutdown.target it is started too late for some complex operation.
Almost all services are stopped, tmpfs are unmounted and filesystems are remounted RO.

<code ini>
[Unit]
Description=Disable power output
DefaultDependencies=no
After=enable-power.service another-enable-power.service
Conflicts=enable-power.service another-enable-power.service
Before=shutdown.target reboot.target halt.target kexec.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/bin/power_control disable

[Install]
WantedBy=shutdown.target
WantedBy=reboot.target
WantedBy=halt.target
WantedBy=kexec.target
</code>


==== run service in reverse order  ====

Trick is to provide service without ''ExecStart='' action only to provide
correct ordering for ''ExecStop='' action.
    
From ''systemd.unit'' doc:
    
    When two units with an ordering dependency between them are shut down,
    the inverse of the start-up order is applied
    
    Most importantly, for service units start-up is considered completed for
    the purpose of Before=/After= when all its configured start-up commands
    have been invoked and they either failed or reported start-up success


<code ini>
[Unit]
Description=Disable power output
DefaultDependencies=no

# Shedule it BEFORE to run ExecStop AFTER during shutdown
Before=enable-power.service

# Want to run ExecStop after eley-device is stopped
Before=another-enable-power.service

Before=basic.target
After=sysinit.target local-fs.target

Before=shutdown.target reboot.target halt.target kexec.target
Conflicts=shutdown.target reboot.target halt.target kexec.target


[Service]
Type=oneshot
RemainAfterExit=yes
ExecStop=/bin/power_control disable
ExecStop=/bin/true


[Install]
WantedBy=basic.target
</code>