What I want
I have a systemd service that I would like to have stopped before suspend/shutdown, and start up again after resume.
System details below.
$ lsb_release -dc
Description: Ubuntu 20.04.1 LTS
$ systemd --version
systemd 245 (245.4-4ubuntu3.3)
+PAM +AUDIT +SELINUX +IMA +APPARMOR +SMACK +SYSVINIT +UTMP +LIBCRYPTSETUP +GCRYPT +GNUTLS +ACL +XZ +LZ4 +SECCOMP +BLKID +ELFUTILS +KMOD +IDN2 -IDN +PCRE2 default-hierarchy=hybrid
What I have so far
I have two services,
myservice-suspend.service respectively starting and stopping a python process at suspend and resume. The python script issues commands to an SDK server that controls RGB lighting. When on is passed as an argument (as in ExecStart), the process must be left running in the background to keep issuing commands as part of a loop. When the process catches a SIGINT signal the lighting is switched off and gracefully exits. In this setup, myservice-suspend.service is triggered before suspend and causes stopping of
myservice-resume.service due to conflict.
Description=Start myservice-resume.service after suspend and shutdown
ExecStart=/path/to/python3 /path/to/script.py on
Description=Stop myservice-resume.service before suspend and shutdown
In this setup, I start the service (and lighting) using
systemctl start myservice-resume.service and successfully turn off lighting using
systemctl start myservice-suspend.service,
systemctl stop myservice-resume.service, or by doing a system suspend using
systemctl suspend. I'd like to have the first service,
myservice-resume.service, automatically start again on system resume. I'd imagine that this would involve adding some clever After/Before/WantedBy targets in the [Unit] and [Install] sections, but I can't determine an appropriate way to set this up.
Research/What I've tried
A related post (Systemd: stop service before suspend, restart after resume) hinted that I could configure a service to run after resume from suspend by adding
After=suspend.target to the Unit section of
myservice-resume.service. I've tried this, but the systemctl log shows that the unit was not started again on resume.
This post (Writing systemd unit file for suspend/resume) points the OP to the systemd man pages to come up with a solution (and clarifies the purpose of After/WantedBy), but I couldn't find a solution here either.