c27 the boot process

8/12/2019 C27 the Boot Process

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PC Hardware Servicing

Chapter 27: The Boot Process


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Chapter 27 Objectives

Understand bootable disks

Identify key boot files in each OS version

List the boot sequence for each OS

Use alternative boot modes

Create and use a boot floppy

Use the Recovery Console

Create and use an ERD

Troubleshoot startup and shutdown problems


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What Constitutes a Bootable Disk?

A disk that can bring the PC to a functional

level, with the OS ready to accept user

commands


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Startup Configuration Files for DOS

CONFIG.SYS Used primarily under MS-DOS

Plain text file

Lists environment variables and device drivers Runs only at startup

AUTOEXEC.BAT Used primarily under MS-DOS

Plain text file Lists applications to run at startup

Simple batch file, can be rerun at any time


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Sample CONFIG.SYS


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Sample AUTOEXEC.BAT


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Startup Configuration Files for

Windows 3.x

SYSTEM.INI

Loads device drivers

Defines environment variables

WIN.INI Loads applications

Sets display settings and I/O device settings

Defines application settings


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Sample SYSTEM.INI


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Sample WIN.INI


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The Registry

32-bit versions of Windows systemsettings files

In Windows 9x:SYSTEM.DAT and

USER.DAT In Windows NT/2000/XP:SAM,

SECURITY, SYSTEM, SOFTWARE,

DEFAULT Accessed through the Registry Editor as a

single database


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MS-DOS Boot Sequence

1. BIOS performs POST

2. BIOS searches for master boot record (MBR),which defines the active partition

3. MBR takes control and locates IO.SYS

4. IO.SYS takes control, identifies hardware

5. IO.SYS runs CONFIG.SYS

6. MSDOS.SYS takes control, loads OS kernelinto RAM

7. MSDOS.SYS runs AUTOEXEC.BAT

8. Command.com displays a command prompt


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Windows 9x Boot Sequence

1.BIOS performs POST

2.BIOS searches for MBR

3.MBR takes control and locates IO.SYS

4. IO.SYS takes control, runs MSDOS.SYS

instructions

5. IO.SYS loads LOGO.SYS (graphic file) and

displays it as Windows splash screen6. IO.SYS looks for SYSTEM.DAT and USER.DAT

and checks them


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7. IO.SYS loads SYSTEM.DAT

8. IO.SYS executes CONFIG.SYS and

AUTOEXECB.BAT if present

9. IO.SYS loads HIMEM.SYS

10.IO.SYS loads WIN.COM

11.Win.COM loads 386.VXD (virtualmemory manager)

12.VMM386.VXD loads 32-bit device drivers


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13.WIN.COM processes SYSTEM.INI if

present

14.WIN.COM loads KRNL32.DLL, GDI.EXE,

and USER.EXE

15.WIN.COM executes WIN.INI if present

16.WIN.COM runs any programs fromStartup folder on Start menu


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Alternative Boot Modes for Windows 9x

Press F8 as PC is starting up to see

Startup Menu


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Alternative Boot Modes for Windows 9x


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Safe Mode

Minimalset ofdrivers

StandardVGAdriver

No

supportfor CD,sound,modems


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Step by Step Confirmation

Accept or reject each line of the startup


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Windows NT, 2000, and XP Boot

Sequence

1. BIOS performs POST

2. BIOS searches for MBR

3. MBR takes control and locates NTLDR

4. NTLDR switches CPU into 32-bit protectedmode

5. NTLDR reads BOOT.INI. If multiple OSes, itdisplays a menu for user choice, and passes

control to the chosen OS6. NTLDR runs NTDETECT.COM, which detects

the hardware for Registry


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Windows NT, 2000, and XP Boot

Sequence

7. NTLDR reads NTOSKRNL (OS kernel)

into memory

8. NTLDR locates drivers for Registry-

reported hardware

9. NTLDR hands over control to

NTOSKRNL.EXE

10.NTOSKRNL.EXE loads the device

drivers and the GUI


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Alternative Boot Modes for NT 4

VGA mode


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Alternative Boot Modes for Windows 2000

and XP


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Troubleshooting 9x Startup

No operating system found

No bootable disk is available

PC does not see hard drive

Hard drive not formatting No OS installed

Loose connection to hard disk

Physical malfunction Virus infection

IO.SYS or MSDOS.SYS missing or corrupted


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Error in CONFIG.SYS Line xx

Driver called for in CONFIG.SYS missing or

corrupted

Bad or Missing COMMAND.COM

Stuck at Windows splash screen

Press Esc to see what is going on behind it

Disable virtual memory

Rebuild paging file


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Missing, Corrupt, or UnloadedHIMEM.SYS

Windows protection error

Virtual device driver problem Start in Safe Mode and check for a real-mode

driver on CONFIG.SYS

Remove and reinstall the device

Device referenced in SYSTEM.INI orWIN.INI not found


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General protection fault (GPF)

Two programs try to use the same memory

space

Make a note of the file causing the error, andrestart

If repeats, try reinstalling the associated

program or using EXTRACT to re-copy filefrom Windows disc


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Troubleshooting 2000/XP Startup

Try Safe Mode

Try restoring last known good

configuration

If Windows XP, use System Restore

Repair Windows installation by booting

from Setup CD and choosing Repair


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Controlling What Loads at Startup

Disable items inWIN.INI,SYSTEM.INI,

AUTOEXEC.BAT,and CONFIG.SYSthrough the

SystemConfigurationEditor (SYSEDIT)


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Delete items from Startup folder on Start menu


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Use System

Configuration Utility

(MSCONFIG) to

disable startup

items


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Creating a 9x Startup Floppy

1. Open Control Panel

2. Add/Remove Programs, Startup Disk tab

3. Click Create Disk and follow the prompts


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How a Boot Floppy Works

1.Booting from floppy creates RAM disk

2.Compressed files are decompressed onto

RAM disk

Therefore some utilities are directly on

the floppy, and others are on the RAM disk


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Files on a Boot Floppy

DRVSPACE.BIN:Support for hard disks compressedwith DriveSpace

EBD.CAB:The compressed file containing extra utilitiesto be placed on RAM disk

AUTOEXEC.BATand CONFIG.SYS

FINDRAMD.EXE:Locates the RAM disk

EXTRACT.EXE:Extracts compressed files to RAM disk

FDISK:Partitions disks README.TXT:Information

CD-ROM drivers


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Files on the RAM Disk


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What is an ERD?

Emergency Repair Disk

For Windows 2000/XP only

Not bootable

Stores settings that can help repair

Windows, along with Windows Setups

Repair mode

Specific to that PC


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Creating an ERD

1. Start the

Backup

application

2. Click theEmergency

Repair Disk

button

3. Follow the

prompts


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What Is the Recovery Console?

Command-line interface

Limited set of commands

Accessible even when Windows will notstart normally

Can repair the MBR, disable services, etc.


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Booting to the Recovery Console

1.Boot from the Windows CD

2.Choose R for Repair

3.Choose C for Recovery Console

4.Type 1 to choose the Windows installation

5.Enter administrator password whenprompted


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Recovery Console Commands

ATTRIB

CD MD

COPY

DEL

CHKDSK

DIR

EXIT EXPAND

FORMAT

MD

RD

REN

Some are same as with Win9x startup disk:


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Recovery Console Commands

Some are different from normal commandprompt commands:

BATCH

DISABLE DISKPART

ENABLE

FIXBOOT

FIXMBR

LISTSYS


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Troubleshooting Shutdown

Problems

Does not shut off with Shut Down

command

Is ACPI enabled in BIOS Setup?

Is it an ATX motherboard?

Is ACPI enabled in Windows?

Are case wires connected to motherboard?

Is a BIOS update available for motherboard?


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Problems

Application Not Responding

Click End Task if dialog box appears

Press Ctrl+Alt+Delete and shut down

application

No Shutdown with Power Button

Hold power button down for 5 seconds


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Problems

Windows 98 locks up when shutting down

Download patch for Windows 98

Disable Fast Shutdown (in MSCONFIG)

c27 the boot process

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