More playing around with FreeBSD inside VirtualBox today. Upgraded the virtual defake to the latest 9.1-BETA kernel and... it wouldn't boot. They've recently done a dirty trick and changed the name of the disk driver, so the boot disk became /dev/ada0 instead of /dev/ad0. The loader had no difficulty loading the kernel, but then the entries in /etc/fstab were wrong, and the root mount failed.
That's OK: the loader enables you to tell it where the root file system is:
But that didn't work:
mountroot: waiting for device ufs:/dev/ada0s1a ...
Mounting from ufs:/dev/ada0s1a failed with error 19.
Error 19 is ENODEV, operation not supported by device, not necessarily the most obvious error indication. Looking at the output of the list command, it seems that the kernel doesn't recognize the disk:
cd0 ada0
I should have seen ada0s1a there, but there's just the base disk. This isn't the first time I've had problems here, and I'm not sure what's causing them. Time to download an ISO and try from there.