Systemd : How to execute script at shutdown only (not at reboot)

Question

There is a lot of solution here to execute a script at shutdown/reboot, but I want my script to only execute at shutdown.

I've tried to put my script in /usr/lib/systemd/systemd-shutdown, and check the $1 parameter, as seen here, but it doesn't work.

Any ideas ?

system : archlinux with gnome-shell

$systemctl --version                                                                                                                                                                                 
systemd 229
+PAM -AUDIT -SELINUX -IMA -APPARMOR +SMACK -SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN

Answer 1

I've finally found how to do that.

It's a bit hackish thought, but it works.

I've used some part of this thread : https://stackoverflow.com/questions/25166085/how-can-a-systemd-controlled-service-distinguish-between-shutdown-and-reboot

and this thread : How to run a script with systemd right before shutdown?

I've created this service /etc/systemd/system/shutdown_screen.service

[Unit]
Description=runs only upon shutdown
Conflicts=reboot.target
After=network.target

[Service]
Type=oneshot
ExecStart=/bin/true
ExecStop=/bin/bash /usr/local/bin/shutdown_screen
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Which will be executed at shudown/reboot/halt/whatever. (don't forget to enable it)

And in my script /usr/local/bin/shutdown_screen I put the following :

#!/bin/bash
# send a shutdown message only at shutdown (not at reboot)    
/usr/bin/systemctl list-jobs | egrep -q 'reboot.target.*start' || echo "shutdown" | nc 192.168.0.180 4243 -w 1

Which will send a shutdown message to my arduino, whom will shutdown my screen.

Answer 2

According to the systemd.special man-page, you should use Before=poweroff.target.

poweroff.target

A special target unit for shutting down and powering off the system.

Applications wanting to power off the system should start this unit.

runlevel0.target is an alias for this target unit, for compatibility with SysV.

Additionally, as I mentioned in my comment, you should put custom scripts into /etc/systemd/system/. The /usr/lib/systemd/system/ directory is meant to be used for system-provided scripts.

So, maybe something like this:

[Unit]
Description=runs only upon shutdown
DefaultDependencies=no
Conflicts=reboot.target
Before=shutdown.target
Requires=poweroff.target

[Service]
Type=oneshot
ExecStart=/bin/true
ExecStop=/usr/local/bin/yourscript
RemainAfterExit=yes