I recently upgraded to Fedora Core 6 on my HP OmniBook XE3 but found a trouble to shutdown the system. Part of the messages are below:

Halting system...
md: stopping all md devices
shutdown:hda
system halted

Then nothing happens so I have to turn off the power in order to shutdown the system.

Any idea where should I take a look? Thanks!

Did you confirm the ACPI is supportted in your system?
Try command "halt -p" or "init 0"

I tried both and the same problem is still there. Thanks. It seems that my laptop doesn't support acpi. But I don't have such problems running Fedora Core 4 before I upgraded to 6.

I had a similar problem with my Shuttle ak31 v2 motherboard. First off, this motherboard must not handle ACPI correctly. Ever since FC2 I've had to use "acpi=off" in the grub.conf which disables ACPI in Linux, but everything worked fine (it uses APM instead) in FC2, FC3, FC4 and FC5. Once I upgraded to FC6, however, Fedora would no longer turn off the power on my PC when I shut it down. It would just stop, with the last message on the screen being "System halted.". After much googling I found this page, http://mandrivausers.org/index.php?showtopic=38210
which recommended adding "acpi=off apm=on apm=power-off" to the grub.conf. Since my acpi was already off, and I new my APM was already on I simply had to add "apm=power-off" to my grub.conf and now Linux will shut the power off on my PC after it shuts down!

My relevant grub.conf entry now looks like this:

title Fedora Core (2.6.19-1.2895.fc6)
root (hd0,1)
kernel /boot/vmlinuz-2.6.19-1.2895.fc6 ro root=/dev/hda2 selinux=0 vga=791 acpi=off apm=power-off elevator=anticipatory
initrd /boot/initrd-2.6.19-1.2895.fc6.img
savedefault

Hope this info helps.