Just edit yout fstab file with new device drive name when hdd running on old PC before moving to new. That's all, it will boot successfully. But if you already have only hdd and don't have old PC...
Everything below is example!
Before to start anything you need to explore your hdd partitioning precisely. After moving to new PC you need to pay attention during boot process at which device appears this hdd. Assume it's really ad4. And hdd partitioning is standard, single slice and so on. Then point boot loader to your hdd root partition
After mounting will complete you'll get request for password and shell. Then you need to remount partitions manually with write permissions in order to get access to userland utilities. Process this accordingly your partitioning scheme, below is for example only
Ignore error messages.
Code:
/sbin/mount /dev/ad4s1d /tmp
/sbin/mount /dev/ad4s1e /var
/sbin/mount /dev/ad4s1e /usr
Nou you can edit your fstab any convinient to you way.
Code:
cd /etc
cp fstab fstab-old
/usr/bin/sed -i bak 's/ad0/ad4/g' fstab
/sbin/reboot
Explanation. Copy original fstab to fstab-old in order to have possibility to revert if something goes wrong. Replace with sed all occurences of ad0 to ad4 in-place and saves .bak file.
That's all. Should to work now. If all names and partitions observed to real situation.
Check for keys and utilities online or in manual pages.
