1. install RAID1 version of NetBSD to scratch two disks
   (http://www.ki.nu/~makoto/p16/20161225/)
   (http://www.ki.nu/~makoto/p16/20161226/)
   (http://www.ki.nu/~makoto/p17/20171119/?photo=0896&size=640x480)
2. and then, boot (to upgrade) from USB image

In that case, sysinst does not started, but regular multiuser mode started with

1. kernel is newer
2. disk are still old ones.

How do I start Memory disk kernel and sysinst ?
should I copy netbsd-INSTALL.gz onto /netbsd.install ? and boot netbsd.install ?

ms09$ sudo mount /dev/sd0a /mnt
ms09$ sudo cp  -p /mnt/amd64/binary/kernel/netbsd-INSTALL.gz  /

this does not work. The original problem was that the kernel are OK, but fails to mountroot ? (mounting existing hard disk)