recovering system from mountroot

After a power failure, my system 10.2 (updated to 11, IIRC) delivers me to

rootmount> and reports that / was not properly dismounted.

? returns /dev/ada0p1, /dev/ada0p2, /dev/ada0p3. (boot,root,swap respectively).

I can do ufs:/dev/ada0p2, to get to a shell; find / -name fstab then gives no result.

Why do I see no fstab?
How can I recover the system to normal booting?
Apparently, fsck requires an fstab

...however, works with -y option.

After running this on /dev/ada0p2, the system still goes to mountroot>
fsck /dev/ada0p1 returns, bad superblock message, error 22, an ioctl error message.
fsck /dev/ada0p2 returns segmentation fault errors

Should I be concerned about the absence of fstab?

halt gives device not configured
I seem not to have /etc at all, (and so cannot use mount - for a usb drive - with the same instructions as I would normally).
Supposing that the absence of fstab is the first problem to address...meanwhile I'm not clear where to go for docs on recovery using mountroot?