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DESCRIPTION

Cold starts. Most PCs attempt to boot first from hard disk drive 0 (sometimes known as drive C:) and, failing that, from various other mass storage devices. Usually, BIOSes allow you to change this default sequence, and typically also include a CD-ROM drive as a boot device.

Newer PCs boot using UEFI firmware, not legacy BIOS. That process is described in uefi(8).

By default, a three-stage bootstrap is employed, and control is automatically passed from the boot blocks (bootstrap stages one and two) to a separate third-stage bootstrap program, loader(8). This third stage provides more sophisticated control over the booting process than it is possible to achieve in the boot blocks, which are constrained by occupying limited fixed space on a given disk or slice.

However, it is possible to dispense with the third stage altogether, either by specifying a kernel name in the boot block parameter file, /boot.config, or, unless option -n is set, by hitting a key during a brief pause (while one of the characters -, \, |, or / is displayed) before loader(8) is invoked. Booting will also be attempted at stage two, if the third stage cannot be loaded.

The remainder of this subsection deals only with the boot blocks. The loader(8) program is documented separately.

After the boot blocks have been loaded, you should see a prompt similar to the following:

DragonFly boot
0:ad(0,a)/boot/loader:

The automatic boot will attempt to load /boot/loader and if that fails /loader from partition ‘a’ of either the floppy or the hard disk. This boot may be aborted by typing any character on the keyboard at the ‘boot:’ prompt. At this time, the following input will be accepted:

?

Give a short listing of the files in the root directory of the default boot device, as a hint about available boot files. (A ? may also be specified as the last segment of a path, in which case the listing will be of the relevant subdirectory.)

bios_drive:interface(unit,part) filename [-aCcDdghmnPprsVv]

Specify boot file and flags.

bios_drive

The drive number as recognized by the BIOS. 0 for the first drive, 1 for the second drive, etc.

interface

The type of controller to boot from. Note that the controller is required to have BIOS support since the BIOS services are used to load the boot file image.

The supported interfaces are:

ad

ST506, IDE, ESDI, RLL disks on a WD100[2367] or lookalike controller

fd

5 ¼" or 3 ½" High density floppies

da

SCSI disk on any supported SCSI controller

unit

The unit number of the drive on the interface being used. 0 for the first drive, 1 for the second drive, etc.

part

The partition letter inside the BSD portion of the disk. See disklabel(8). By convention, only partition ‘a’ contains a bootable image. If sliced disks are used (“fdisk partitions”), any slice can be booted from, with the default being the active slice or, otherwise, the first DragonFly slice.

filename

The pathname of the file to boot (relative to the root directory on the specified partition). Defaults to /boot/kernel. Symbolic links are not supported (hard links are).

-aCcDdghmnPprsVv

Boot flags:

-a

during kernel initialization, ask for the device to mount as the root file system.

-C

boot from CDROM.

-D

Use all available consoles as the system console. Input will be accepted on any console and output will be routed to all of them. This is the default.

-h

Use the serial console as the system console.

-V

Use the video console as the system console.

-m

Mute the system console. None of the console devices will be used for the system console.

-d

enter the DDB kernel debugger (see ddb(4)) as early as possible in kernel initialization.

-g

use the GDB remote debugging protocol.

-n

ignore key press to interrupt boot before loader(8) is invoked.

-P

probe the keyboard. If no keyboard is found, the -D and -h options are automatically set.

-p

pause after each attached device during the device probing phase.

-r

use the statically configured default for the device containing the root file system (see config(8)). Normally, the root file system is on the device that the kernel was loaded from.

-s

boot into single-user mode; if the console is marked as “insecure” (see ttys(5)), the root password must be entered.

-v

be verbose during device probing (and later).

You may put a BIOS drive number, a controller type, a unit number, a partition, a kernel file name, and any valid option in /boot.config to set defaults. Enter them in one line just as you type at the ‘boot:’ prompt.