We had a hard drive (FC) mismatch and had to rebuild the path_to_inst file and /dev/rdsk/*, /dev/dsk/* and /dev/rmt/* directories. We had two drives (but the backup drive was inoperable), so instead of booting off the backup, we had to recover via cdrom. That part was a little trickier than expected. After a little web searching, a handy disaster discovery procedure (hardware mismatch) was found on the Sun BigAdmin site.

Method 1 (towards the bottom of the Sun page)

Here is what was done.

Boot from CDROM
ok boot cdrom -s
# mount /dev/dsk/c1t#d#s0 /mnt
Rename path_to_inst
# mv /mnt/etc/path_to_inst /mnt/etc/path_to_inst.org
Remove all old device links
# rm /mnt/dev/rdsk/c1*; rm /mnt/dev/dsk/c1*; rm /mnt/dev/rmt/*
Rebuild path_to_inst and devices (this (syntax) was the part we were missing)
# devfsadm -r /mnt -p /mnt/etc/path_to_inst
**Note: Suspect corrupted bootblock? - reinstall it.
# cd /mnt/usr/platform/`uname -i`/lib/fs/ufs
# /mnt/usr/sbin/installboot bootblk /dev/rdsk/c1t#d#s0
Unmount root slice and reboot
# cd /
# umount /mnt; init 6

By the way, we tried method two (boot -rav) prior to performing the web search but each attempt failed.