FreeBSD 10.1 encrypted root-on-ZFS without passphrase

[Julian Hsiao]

Hi,

I'm trying to install FreeBSD 10.1 with all partitions (except /boot, 
of course) encrypted, but without a passphrase.  I chose "Auto (ZFS)" 
and then "Encrypt Disks? YES" in the installer, entered a dummy 
passphrase, and proceeded with the rest of the install.  Afterwards, I 
dropped into the manual configuration shell:

# zpool status zroot | grep eli | cut -w -f 2
ada0p4.eli
# geli setkey -k /boot/encryption.key -K /boot/encryption.key -P ada0p4
Note, that the master key encrypted with old keys and/or passphrase may 
still exists in a metadata backup file.
# geli configure -B ada0p4
# exit

However, upon reboot I get this error during startup:

Trying to mount root from zfs:zroot/ROOT/default []...
Mounting from zfs:zroot/ROOT/default failed with error 2.

If I omit "geli configure -B" during manual configuration, then I'd be 
prompted for a passphrase during boot, but no passphrase would work.  
I'm pretty sure the passphrase was removed, however, since I also tried 
to unlock the partition with a working system with just "geli attach -p 
-k" and that worked.

I also tried adding to loader.conf:

geli_ada0p4_flags=" -p"

And that didn't help.  What else am I overlooking?