boot —
system bootstrapping procedures
This document provides information on using common features in the
  NetBSD boot loader. Additional information may be
  found in architecture-specific
  boot(8) manual pages.
In the native NetBSD boot protocol, options are passed
  from the boot loader to the kernel via flag bits in the
  boothowto variable (see
  boothowto(9)). Some boot
  loaders may also support other boot protocols.
Some boot loaders may present a menu, which may be configured via
  boot.cfg(5).
In interactive mode, the boot loader will present a prompt, allowing input of
  these commands:
  - boot[device:][filename]
    [- -1234abcdmqsvxz]
- The default device will be set to the disk that the
      boot loader was loaded from. To boot from an alternate disk, the full name
      of the device should be given at the prompt. device
      is of the form xd
      [N[x]] where
      xd is the device from which to boot,
      N is the unit number, and x is
      the partition letter.
    The following list of supported devices may vary from
        installation to installation: 
      - hd
- Hard disks.
- fd
- Floppy drives.
 The default filename is
        netbsd; if the boot loader fails to successfully
        open that image, it then tries netbsd.gz
        (expected to be a kernel image compressed by gzip), followed by
        netbsd.old,
        netbsd.old.gz, onetbsd,
        and finally onetbsd.gz. Alternate system images
        can be loaded by just specifying the name of the image. Options are: 
      - -1
- Sets the machine-dependent flag RB_MD1 in
          boothowto.
- -2
- Sets the machine-dependent flag RB_MD2 in
          boothowto.
- -3
- Sets the machine-dependent flag RB_MD3 in
          boothowto.
- -4
- Sets the machine-dependent flag RB_MD4 in
          boothowto.
- -a
- Sets the RB_ASKNAME flag in
          boothowto. This causes the kernel to prompt for
          the root file system device, the system crash dump device, and the
          path to init(8).
- -b
- Sets the RB_HALT flag in
          boothowto. This causes subsequent reboot
          attempts to halt instead of rebooting.
- -c
- Sets the RB_USERCONF flag in
          boothowto. This causes the kernel to enter the
          userconf(4) device
          configuration manager as soon as possible during the boot.
          userconf(4) allows
          devices to be enabled or disabled, and allows device locators (such as
          hardware addresses or bus numbers) to be modified before the kernel
          attempts to attach the devices.
- -d
- Sets the RB_KDB flag in
          boothowto. Requests the kernel to enter debug
          mode, in which it waits for a connection from a kernel debugger; see
          ddb(4).
- -m
- Sets the RB_MINIROOT flag in
          boothowto. Informs the kernel that a mini-root
          file system is present in memory.
- -q
- Sets the AB_QUIET flag in
          boothowto. Boot the system in quiet mode.
- -s
- Sets the RB_SINGLE flag in
          boothowto. Boot the system in single-user
        mode.
- -v
- Sets the AB_VERBOSE flag in
          boothowto. Boot the system in verbose mode.
- -x
- Sets the AB_DEBUG flag in
          boothowto. Boot the system with debug messages
          enabled.
- -z
- Sets the AB_SILENT flag in
          boothowto. Boot the system in silent mode.
 
- consdevdev
- Immediately switch the console to the specified device
      dev and reprint the banner.
      dev must be one of pc,
      com0, com1,
      com2, com3,
      com0kbd, com1kbd,
      com2kbd, com3kbd, or
      auto. See
      Console Selection
      Policy in
      x86/boot_console(8).
- dev[device]
- Set the default drive and partition for subsequent filesystem operations.
      Without an argument, print the current setting.
      device is of the form specified in
      boot.
- help
- Print an overview about commands and arguments.
- ls[path]
- Print a directory listing of path, containing
      inode number, filename, and file type. path can
      contain a device specification.
- quit
- Reboot the system.
 
In an emergency, the bootstrap methods described in the
    NetBSD installation notes for the specific
    architecture can be used.
  - /boot
- boot program code loaded by the primary bootstrap
- /netbsd
- system code
- /netbsd.gz
- gzip-compressed system code
- /usr/mdec/boot
- master copy of the boot program (copy to /boot)
- /usr/mdec/bootxx_fstype
- primary bootstrap for filesystem type fstype, copied to the start of the
      NetBSD partition by
      installboot(8).
Architecture-specific boot(8) manual
  pages (such as
  emips/boot(8),
  sparc64/boot(8),
  x86/boot(8)),
  ddb(4),
  userconf(4),
  halt(8),
  installboot(8),
  reboot(8),
  rescue(8),
  shutdown(8),
  boothowto(9)
The kernel file name must be specified before, not after, the boot options. Any
  filename specified after the boot options, e.g.:is ignored, and the default kernel is booted.