boot —
system bootstrapping procedures
Normally, the system will reboot itself at power-up or after crashes. An
  automatic consistency check of the file systems will be performed as described
  in fsck(8), and unless this
  fails, the system will resume multi-user operations.
The prep architecture does not allow the direct booting of a kernel from the
  hard drive. Instead it requires a complete boot image to be loaded. This boot
  image contains a NetBSD kernel, which will then
  provide access to the devices on the machine. The image can be placed on any
  device that the firmware considers a bootable device. Usually this is either a
  SCSI disk, tape, CD-ROM, or floppy drive.
The prep architecture and bootloader does not support any option parsing at the
  boot prompt.
The prep port requires a special boot partition on the primary boot device in
  order to load the kernel. This partition consists of a PC-style i386 partition
  label, a small bootloader, and a kernel image. The prep firmware looks for a
  partition of type 0x41 (65) and expects the bootloader, immediately followed
  by the kernel, to be there. The
  prep/mkbootimage(8)
  command needs to be used to generate this image.
  - /netbsd
- system code
- /usr/mdec/boot
- system bootstrap
- /usr/mdec/boot_com0
- system bootstrap with serial console