Those are the commands I use to tell OSX to use my second hard drive as the
/Users mount point.
# cd /Users
# tar cpf – . | tar xpf – -C /Volumes/Utilisateurs/
# diskutil info /Volumes/Utilisateurs
# cat /etc/fstab
UUID=D6AEEE52-89D7-34CE-A23B-6E81F76E54B1 /Users hfs rw 1 0
UUID=ED1DAC49-5CB4-3F69-B8E9-342BBC20C5ED none hfs rw,noauto 0 0
One might reboot in single-user mode to delete the previous
/Users content. I personally prefer to leave it untouch in case something happens to my second disk. This would enable an easy start from the first disk only.