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.
consdev
dev
- 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.