When closing the lid of a laptop on FreeBSD, the screen will go blank and that is about it, the laptop will stay running as usual, what we really want is for the laptop to suspend when the lid is closed in order to save on battery. Unlike Linux, OpenBSD and other operating systems, FreeBSD does not provide this functionality by default.
We must edit a file in /etc called /etc/sysctl.conf. This
file should be present but empty by default on FreeBSD. All we need to add
to this file is the line hw.acpi.lid_switch_state=S3, and
reboot.
Alternativly, if you do not wish to reboot, running the
command sysctl hw.acpi.lid_switch_state=S3 as root should
provide this funtionality.
NOTE: I have only tested this
on a ThinkPad X200 which is a very well supported laptop by nearly
every single operating system, so your laptop might not work with this
specific setting, I will update this page as I test this with other
laptops.