FreeBSD Architecture Handbook
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# 1.2 Overview

A computer running FreeBSD can boot by several methods, although the most common method, booting from a harddisk where the OS is installed, will be discussed here. The boot process is divided into several steps:

- BIOS POST

- `boot0` stage

- `boot2` stage

- loader stage

- kernel initialization

The `boot0` and `boot2` stages are also referred to as bootstrap stages 1 and 2 in boot(8) as the first steps in FreeBSD's 3-stage bootstrapping procedure. Various information is printed on the screen at each stage, so you may visually recognize them using the table that follows. Please note that the actual data may differ from machine to machine:

Output (may vary) | BIOS (firmware) messages

    F1    FreeBSD
    F2    BSD
    F5    Disk 2

`boot0`

    >>FreeBSD/i386 BOOT
    Default: 1:ad(1,a)/boot/loader
    boot:

`boot2`a

    BTX loader 1.0 BTX version is 1.01
    BIOS drive A: is disk0
    BIOS drive C: is disk1
    BIOS 639kB/64512kB available memory
    FreeBSD/i386 bootstrap loader, Revision 0.8
    Console internal video/keyboard
    (jkh@bento.freebsd.org, Mon Nov 20 11:41:23 GMT 2000)
    /kernel text=0x1234 data=0x2345 syms=[0x4+0x3456]
    Hit [Enter] to boot immediately, or any other key for command prompt
    Booting [kernel] in 9 seconds..._

loader

    Copyright (c) 1992-2002 The FreeBSD Project.
    Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
            The Regents of the University of California. All rights reserved.
    FreeBSD 4.6-RC #0: Sat May  4 22:49:02 GMT 2002
        devnull@kukas:/usr/obj/usr/src/sys/DEVNULL
    Timecounter "i8254"  frequency 1193182 Hz

kernel

Notes: a. This prompt will appear if the user presses a key just after selecting an OS to boot at the `boot0` stage.

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