I’ve had this question a few times, so it’s probably a good candidate for my blog.
If you want to do something before you suspend, like unload a module or run some script, it’s quite easy with systemd. Similarly, you can easily do something when the system resumes (like reload the module).
The details are in the systemd-suspend man page:
man systemd-suspend.service
Simply put an executable script of any name under /usr/lib/systemd/system-sleep/ that checks whether the first argument is pre (for before the system suspends) or post (after the system wakes from suspend).
If it is pre, then do the thing you want to before suspend, if it’s post then do the thing you want to do after resume. Simple!
Here’s a useless example:
#!/bin/sh
if [ "${1}" == "pre" ]; then
# Do the thing you want before suspend here, e.g.:
echo "we are suspending at $(date)..." > /tmp/systemd_suspend_test
elif [ "${1}" == "post" ]; then
# Do the thing you want after resume here, e.g.:
echo "...and we are back from $(date)" >> /tmp/systemd_suspend_test
fi