>
and its clones
(the)
that can run
NetBSD/i386
can use any of the following boot procedures, depending on what the hardware and
BIOS
support:
- boot
-
bootstrap
NetBSD
from the system
BIOS
- dosboot(8)
-
bootstrap
NetBSD
from
MS-DOS
- w95boot(8)
-
bootstrap
NetBSD
from
Windows 95
- pxeboot(8)
-
network bootstrap
NetBSD
from a
TCP/IP
LAN
with
DHCP,
TFTP,
and
NFS.
Power fail and crash recovery
Normally, the system will reboot itself at power-up or after crashes.
An automatic consistency check of the file systems will be performed,
and unless this fails, the system will resume multi-user operations.
Cold starts
The 386
PC AT
clones attempt to boot the floppy disk drive A (otherwise known as drive
0) first, and failing that, attempt to boot the hard disk C (otherwise
known as hard disk controller 1, drive 0).
The
NetBSD
bootblocks are loaded and started either by the
BIOS,
or by a boot selector program (such as OS-BS, BOOTEASY, the OS/2 Boot Menu or
NetBSD's
boot-selecting
master boot record - see
mbr(8)).
Normal Operation
Once running, a banner similar to the following will appear:
-
>> NetBSD BIOS Boot, revision 3.0
>> (user@buildhost, builddate)
>> Memory: 637/15360 k
Press return to boot now, any other key for boot menu
booting hd0a:netbsd - starting in 5
After a countdown, the system image listed will be loaded.
In the example above, it will be
``
hd0a:netbsd
''
which is the file
netbsd
on partition
``a''
of the
NetBSD
MBR
partition of the first hard disk known to the
BIOS
IDE
or similar device - see the
BUGS
section
(which is an.)
Pressing a key within the time limit, or before the boot program starts, will
enter interactive mode.
When using a short or 0 timeout, it is often useful to interrupt the boot
by holding down a shift key, as some BIOSes and BIOS extensions will drain the
keystroke buffer at various points during POST.
If present, the file /boot.cfg will be used to configure the behaviour of the
boot loader including setting the timeout, choosing a console device, altering
the banner text and displaying a menu allowing boot commands to be easily
chosen. See
boot.cfg(5).
The
NetBSD/i386
boot loader can boot a kernel using either the native
NetBSD
boot protocol, or the
``multiboot''
protocol (which is compatible with some other operating systems).
In the native
NetBSD
boot protocol, options are passed from the boot loader
to the kernel via flag bits in the
boothowto
variable, which is interpreted by the kernel in much the same way
as the
howto
argument passed to the
reboot(2)
system call.
In the multiboot protocol, options are passed from the boot loader
to the kernel as strings.
Diagnostic Output
If the first stage boot fails to load the boot, it will print a terse
message indicating the reason for the failure.
The possible error messages and their cause are listed in
mbr(8).
If the first stage boot succeeds, the banner will be shown and the
error messages should be self-explanatory.
Interactive mode
In interactive mode, the boot loader will present a prompt, allowing
input of these commands:
- Xo 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
[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 as numbered by the BIOS. This includes
ST506, IDE, ESDI, RLL disks on a WD100[2367] or
lookalike controller(s), and SCSI disks
on SCSI controllers recognized by the BIOS.
- fd
-
Floppy drives as numbered by the BIOS.
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.
In
NetBSD/i386,
this disables multiprocessor boot;
the kernel will boot in uniprocessor mode.
- -2
-
Sets the machine-dependent flag
RB_MD2
in
boothowto.
In
NetBSD/i386,
this disables ACPI.
- -3
-
Sets the machine-dependent flag
RB_MD3
in
boothowto.
In
NetBSD/i386,
this has no effect.
- -4
-
Sets the machine-dependent flag
RB_MD4
in
boothowto.
In
NetBSD/i386,
this has no effect.
- -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
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.
- load module[ arguments]
-
Load the specified kernel
module,
and pass it the specified
arguments.
If the module name is not an absolute path,
/stand/
Xo
<arch>
/
<osversion>
/modules/
<module>
/
<module>
.kmod
is used.
Possible used of the
load
command include loading a memory disk image before booting a kernel,
or loading a Xen DOM0 kernel before booting the Xen hypervisor.
- ls[
path
] -
Print a directory listing of
path
,
containing inode number, filename, and file type.
path
can contain a device specification.
- multiboot kernel[ arguments]
-
Boot the specified
kernel,
using the
``multiboot''
protocol instead of the native
NetBSD
boot protocol.
The
kernel
is specified in the same way as with the
boot
command.
The multiboot protocol may be used in the following cases:
- NetBSD/Xen kernels
-
The Xen DOM0 kernel must be loaded as a module using the
load
command, and the Xen hypervisor must be booted using the
multiboot
command.
Options for the DOM0 kernel (such as
``-s''
for single user mode) must be passed as options to the
load
command.
Options for the hypervisor (such as
``dom0_mem=256M''
to reserve 256 MB of memory for DOM0)
must be passed as options to the
multiboot
command.
See
boot.cfg(5)
for examples of how to boot
NetBSD/Xen.
- NetBSDmultiboot kernels
-
A
NetBSD
kernel that was built with
options MULTIBOOT
(see
multiboot(8))
may be booted with either the
boot
or
multiboot
command, passing the same arguments in either case.
- Non-NetBSDkernels
-
A kernel for a
non-NetBSD
operating system that expects to be booted using the
multiboot protocol (such as by the GNU
``GRUB''
boot loader)
may be booted using the
multiboot
command.
See the foreign operating system's documentation for the available arguments.
- quit
-
Reboot the system.
In an emergency, the bootstrap methods described in the
NetBSD
installation notes for the i386 architecture
can be used to boot from floppy or other media,
or over the network.
FILES
/boot
-
boot program code loaded by the primary bootstrap
/boot.cfg
-
optional configuration file
/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).
SEE ALSO
ddb(4),
userconf(4),
boot.cfg(5),
boot_console(8),
dosboot(8),
halt(8),
installboot(8),
mbr(8),
multiboot(8),
pxeboot(8),
reboot(8),
shutdown(8),
w95boot(8)
BUGS
The kernel file name must be specified before, not after, the boot options.
Any
filename
specified after the boot options, e.g.:
-
boot -d netbsd.test
is ignored, and the default kernel is booted.
Hard disks are always accessed by
BIOS
functions.
Unit numbers are
BIOS
device numbers which might differ from numbering in the
NetBSD
kernel or physical parameters
SCSI
slave numbers
(e.g.,.)
There isn't any distinction between
``sd''
and
``wd''
devices at the bootloader level.
This is less a bug of the bootloader code than
a shortcoming of the PC architecture.
The default disk device's name printed in the starting message
is derived from the
``type''
field of the
NetBSD
disklabel (if it is a hard disk).