BOOT(8)

NAME
boot - system bootstrapping procedures

DESCRIPTION
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, or the OS/2 Boot Menu)

Once running, a prompt similar to the following will appear.

    >> NetBSD BIOS Boot, revision 2.2
    >> (user@buildhost, builddate)
    >> Memory: 637/15360 k
    Use hd1a:netbsd to boot sd0 when wd0 is also installed
    Press return to boot now, any other key for boot menu
    booting wd0a:netbsd - starting in 5

After a countdown the system image listed will be loaded. (In the above example, it will be “wd0a:netbsd” which is the file netbsd on partition “a” of the NetBSD MBR partition of the first non-SCSI hard disk.)

The default disk 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. Alternate system images can be loaded by just specifying the name of the image.

The following list of supported devices may vary from installation to installation:

    sd	SCSI disks on a controller recognized by the BIOS. The unit
    	number is the BIOS device number.
    wd	ST506, IDE, ESDI, RLL disks on a WD100[2367] or
    	lookalike controller(s), as numbered by the BIOS.
    hd	Hard disks as numbered by the BIOS.
    fd	Floppy drives as numbered by the BIOS.

The [-s] flag to the boot loader will bring the system up in single-user mode. The [-a] flag instructs the system to prompt for the location of the root filesystem and the system crash dump device. The [-r] flag instructs the system to use the compiled in value for the root device, not the device the system image was loaded from. The [-d] flag to the boot loader will bring the system up in debug mode. Here it waits for a kernel debugger connect; see ddb(4).

In an emergency, the bootstrap methods described in the NetBSD installation notes for the i386 architecture can be used to boot from floppy.

FILES
/netbsd
    system code
/usr/mdec/biosboot.sym
    boot block (not installed)
/boot
    boot block (installed).

SEE ALSO
boot_console(8), ddb(4), halt(8), installboot(8), reboot(8), shutdown(8), dosboot(8)

BUGS
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 (eg SCSI slave numbers). The distiction into “sd” and “wd” devices at the bootloader level is meaningless and exists for historical reasons.