This article will describe shutdown with pressing power button. This is not long press power button which will cause hardware power off. This will cause interrupt to software.
1 Power button action is suspend
Debian 8's power button action is suspend by default via /etc/acpi/events/powerbtn-acpi-support. This is for laptop setting which can be suspend when closing laptop.
2 Append /etc/acpi/events/powerbtn
If /etc/acpi/events/powerbtn is exists, /etc/acpi/events/powerbtn will be executed instead of /etc/acpi/events/powerbtn-acpi-support.
Append /etc/acpi/events/powerbtn which runs poweroff command. Reboot Debian 8 after appending.
$ sudo su -c 'cat <<EOF > /etc/acpi/events/powerbtn event=button[ /]power action=/sbin/poweroff EOF ' $ sudo reboot
If you want to keep running laptop when closing laptop, like connecting via SSH, change poweroff command to true command in /etc/acpi/events/powerbtn.