halt -p works
but, you could also just use
But, this thread wasn't asking the correct syntax of the shutdown/halt/poweroff commands... It was asking if the shutdown command caused problems due to shutting it down too quickly, and about why F16 was taking so long to shutdown.
There are things that can and will cause delays in shutdown, and sometimes they can be tricky to find since closing the log files are a part of the shutdown procedure. If the hang is after the logs are closed, then you have no means to go back and look to find the cause.
You can boot your system with the kernel options systemd.log_level=debug and systemd.log_target=kmsg and get a little more information if you need to.
You can also save more of the log by dumping it to a different file.
place a shell script in
mount / -orw,remount
dmesg > /dmesg.shutdown
mount / -oro,remount
mark it +x
Then boot with the systemd.log_level=debug and systemd.log_target=kmsg kernel options. You should have your shutdown messages in /dmesg and possibly can see where it is hanging.
Just another note on the shutdown -s mentioned above.. It is a valid shutdown option.... IF you were running Windows.
Edit again to correct typo in script above.