What if path_to_inst is not valid (moved array/controllers)?

You should not rename it to path_to_inst.... as it will recover
that file to the original name.  Rename it to my_inst or something.

boot cdrom -sw

mount root to /mnt

cd /tmp/dev
tar cvpf - . | (cd /mnt/dev; tar xvpf -)

cd /tmp/devices
tar cvpf - . | ( cd /mnt/devices; tar xvpf -)

cd /tmp/root/etc
cp path_to_inst /mnt/etc/path_to_inst
init 0
boot