systemd question

[Tom Horsley]

I've been fooling with the systemctl (unfortunately similar
to the sysctl name) tool, and I see "units" for all the
devices on my system with long names something like
sys-pci-yadda-yadda.device.

I have occasionally wanted the ability to make some bit
of hardware on my system disappear. Don't want linux to
fool with it at all (but don't want to take it apart
and yank the board either :-).

Can I use systemctl to do this? Essentially disable
some device unit so the system won't try to use that
bit of hardware for anything?

Just curious. (Of course what I really want is probably
something at a much lower level - something like a
kernel command line parameter that would make the
initial device enumeration skip the device entirely
as early in the boot process as possible).