I recently had the "pleasure" of installing Debian onto a GPT formatted
SSD in a UEFI way.
Debian 9.4 is systemd territory. On freshly booting, something is
causing a 90 second pause for a process to finish. Presumably, there
is no way for this process to tell systemd that it is finished, and so
systemd inserts this long pause. I think this long pause is to catalog
the disk in the optical drive, should there be one.
When you go to shutdown, if some user is logged in under X, it is happy
to shutdown quickly. But if X is displaying the greeter (so that
someone can login), again we get a 90 second pause in shutdown. For
me, if the greeter is being displayed, shutdown should be fast, and
possibly not is a user is still logged in. Shutdown being initiated by
shutdown -h now
If I am using an external USB disk drive, on the GUI I get popups to
manage the presence of this USB device, even though root has an active
terminal session running and is doing all the work. Not only that, but
the popup on top, doesn't have focus and there is no way to give it
focus to kill it. I do not have KDE installed, I have a few KDE
utilities installed. KDE thinks it needs to be involved in this
changing of devices too.