qemu-system-x86_64 refuses to boot HDD

[Juergen Lock]

In article <1365179827998-5801797.post at n5.nabble.com> you write:
>I have installed qemu-devel-1.1.1_2 and kqemu-kmod-devel-1.4.0.p1_5
>In the past I could boot from the HDD with qemu even if it was running host
>system - ada0p2 is root, but I could still boot to ada0 in qemu. Instead
>now, just a strange error:
>
># qemu-system-x86_64 -hda /dev/ada1 =>
>qemu-system-x86_64: -hda /dev/ada1: could not open disk image /dev/ada1:
>Operation not permitted
>
>Is this a qemu error or a devfs.rules problem?
>[localrules=10]
>add path 'da[0-9]*' mode 0660 group wheel
>add path 'cd[0-9]*' mode 0660 group wheel
>
Hmm you dont have a rule for ada* but usually disk devices are
group operator already so you could also add yourself to that
group.  (And log back in afterwards.)

 But actually up there you were running qemu as root so it's not
a permission problem but probably the anti-foot-shooting protection
needs to be disabled:

	# sysctl kern.geom.debugflags=16

(it protects against writing to mounted geoms and their parents so
now you need to take care not to mount stuff on host and guest at
the same time yourself.)

 HTH, :)
	Juergen