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Windows XP Boot Process

70-270: MCSE Guide toMicrosoft Windows XP Professional

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Booting Windows XP (Page 1)

Boot processphases:

Boot phase begins when computer is firstpowered on

Or begins when Restart is chosen from"Shut Down Windows" dialog box

Windows XP load phases

Begins when boot phase is completed Configuration is selected

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Booting Windows XP (Page 2)

Boot Phase Steps

Power-on self test(POST)

Initial startup

Boot loader

Select operatingsystem

Detect hardware

Select configuration

Windows XP Load Phase

Load the kernel

Initialize the kernel

Services load

Windows XP systemstartup

Log on

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Power-on Self Test (Page 1)

First step in boot sequence (the POST) forany computer with an operating system

Determines: Amount of real memory that exists

Whether or not all necessary hardwarecomponents are present and functioning

The specific tests vary depending on howthe BIOS (Basic Input/Output System) isconfigured

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If POST is successful, computer boots itself

If the tests are unsuccessful, the computer

reports error by: Emitting a series of beeps (number of beeps

identifies the errordiffers from one BIOS toanother)

Also possibly might display error messageand a code on the screen

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Software that performs POST resides incalled the CMOS (complementary metaloxide semiconductor)

Battery-powered chip that also can hold

basic configuration information so POSTcan check installed RAM, number and typeof hard drives, type of keyboard and mouse,the boot sequence (Which drive first?), etc.

In Windows XP, BIOS no longer storesinformation about devices and drivers

connected to system (replaced by the HAL)

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Power-on Self Test

The following screen shows results ofsample successful POST completion

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Power-on Self Test

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After POST completes, each adapter witha BIOS performs its own self-test (POST),i.e.

Video card

SCSI (small computer system interface)cards which are interfaces that provide

much faster data transmission rates thanstandard parallel and serial ports; used for

printers, scanners, etc.

Adapters issue their own reports on monitor

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At this point there still is no operatingsystem in RAM

POST application in the BIOS is in control

Output on screen is in basic, text-only form

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Initial Startup (Page 1)

The BIOS finds the first sector of the firsthard drive which contains the Master BootRecord (MBR) and transfers control to it:

It is the job of MBR ultimately to load the

Ntldr program (the boot loader program)and pass control of the boot process on toit (either directly or indirectly)

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The Master Boot Record (con.):

In FAT partitions, because the boot sectoris only one sector in size, MBR points toanother location on disk which then pointsto the boot loader

In NTFS partitions, boot sectors may be upto 16 sectors in size so it is large enough tostore the code to find the boot loader

If booting from a floppy, the first sectorcontains the partition boot sector

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BIOS stores information as to the order inwhich drives are checked to see which isthe startup drive (as stored in CMOS)

If floppy drive is in the sequence, partition

boot sector is loaded and runs the MBRfrom the floppy

If the floppy does not have a partition bootsector, the message "Non-system disk or

disk error " appears

Remove disk, and turn machine off an then

ondo not rebootto avoid viruses

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Ntldr is stored on the system partition

This is the partition where the MBRexpects to find the system

Ultimately its job is to boot the WindowsXP operating system which is stored onthe boot partition

The system itself actually can be storedon any partition

The system and boot partitions may ormay not be the same

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Boot Loader (Page 1)

Collection of files on system partition usedto initiate loading of operating system

Required files to boot Windows XP areNtldr, Ntdetect.com and Boot.ini

Other optional boot loader programs areBootsect.dos and Ntbootdd.sys

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Windows XP Startup Files

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The boot loader first switches processorinto 32-bit mode

Previously it had been running in real modeas if it were an 8088 or 8086 machine

Next it starts the appropriate file system,FAT, FAT32 or NTFS

The ability to access any of the file systemsis programmed into Ntldr

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Primary functions of the boot loader are to:

1. Select the operating system to load if thereis more than one from which to choose

2. Detect hardware

3. Select a configuration

Ntldr stays in control throughout boot

loader process until it loads and passescontrol to Windows XP kernel (Ntoskrnl.ext)

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Selecting the Operating System

Ntldr reads Boot.ini and displays the Bootselection menu (if necessary)

Contains operating system choices, if morethat one, from which the user may choose

It also is possible from this screen to press to reach the "Troubleshooting and

Advanced Startup" screen (more later) Will auto select first option after a specified

number of seconds

Change default O/S or time in Boot.ini

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Boot Selection Menu

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Detecting Hardware

If the user selects Windows XP (or if it isthe only O/S present), Ntldr executesNtdetect.com

Used to collect a list of hardware currently

installed in computer

From hardware list, creates system profile

Later will be compared to Windows XPRegistry entries for discrepancies thatcould lead to problems

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Selecting a Configuration

Next boot loader selects a configuration

Known as the hardware profile

If there is one hardware profile, it is selected If there is more than one, system tries to

select one that matches detected hardware

If system cannot make automatic selection,

user is prompted for manual selection

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Troubleshooting and Advanced

Startup Options (Page 1)

Windows XP combines the boot andrecovery options of Windows NT andWindows 95/98

Provides several options to restore amalfunctioning system to functional state

Before timer expires, or Windows XP

kernel starts to load, press toaccess Windows Advanced Options Menu

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Startup Options

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Contents of menu may include:

Safe Modeboots Windows XP with onlyminimum system files and drivers

May be able to boot into a functioningsystem when some drivers are corrupted

Might allow replacing or removing theproblem driver before rebooting

Safe Mode with Networkingsame as

above but with networking components

If network drivers are not the problem

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Contents of menu may include (con.):

Safe Mode with Command Promptsameas above but not to the GUI environment

Enable Boot Loggingenables or disables

boot process, and writes details to log fileNtbtlog.txt in %systemroot% folder

Records process of steps between bootmenu and logon prompt which couldprovide clues to which driver, system orprocedure is causing the problem

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Enable VGA Modenormal boot but withonly basic VGA video driver (in case there

is a bad video driver)

Last Known Good Configurationstate ofRegistry during last successful user logon

Could be useful if a new driver or softwarerecently has been installed, or the Registrywas recently modified

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Directory Services Restore Modeonly onWindows XP domain controllers, restores

Active Directory

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Debugging Modenormal boot but sendsdebugging information to another system

over a serial cable

If no other option helps in restoring system,may help determine where in boot processthe problem occurs

Complex information usually used by high-end programmersconsult MicrosoftWindows XP Professional Resource Kit

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*** Activity ***

Try one or more of following boot options(press function key during boot):

Safe Mode

Safe Mode with Command Prompt

Enable VGA Mode

Last Known Good Configuration

Reboot normally when done

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Boot Configuration and Selecting

an Operating System (Page 1)

Controlled through configuration of theBoot.inifile

Located in the root directory of the systempartition (usually drive C:\)

To view the file, uncheck "Hide Protectedoperating system files" in Folder Options

Updated from the "System and Recovery"dialog window on the Advanced tab ofControl Panel's System applet

To Sample"Boot.ini"

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Boot Configuration and Selecting

an Operating System (Page 2)

Used by boot loader to display the list ofavailable operating systems

Consists of two sections: [boot loader] and[operating systems]

To Sample"Boot.ini"

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Sample "Boot.ini"

Return

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Settings:

Timeoutnumber of seconds system waitsfor user to select an operating system

If set to zero (0), the default operating

system is loaded automatically

If set to (-1), waits indefinitely (this value

only can be set in text editoran invalidvalue in System applet in "Control Panel"

Defaultshows path to default O/S

[boot loader]

To Sample"Boot.ini"

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[operating systems] (Page 1)

Lists available operating systems asfollows:

Path to boot partition for operating system

Text displayed in boot loader screen

Optional parameters (switches) provideoptions many of which are equivalent to

"Windows Advanced Options Menus"As well as a few other options

To Sample"Boot.ini"

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Switches:

/BASEVIDEOsame as Enable VGA Mode

/BAUDRATE=nbaud rate for DebuggingMode

/BOOTLOGsame as Enable Boot Logging

/CRASHDEBUGstarts Debugging Mode but

remains inactive until STOP error occurs

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Switches (con.):

/DEBUGstarts Debugging Mode andallows access by the remote computer

/DEBUGPORT={com1|com2|1394}sets

port for Debugging Mode

/FASTDETECT={com1|com2|}specifies

serial ports to skip during hardware scanAll if no port specified

Included in every entry by default when theoperating system is installed

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Switches (con.):

/MAXMEM=nsets maximum RAM O/Scan use

/NOGUIBOOTboots without showing

splash screen

/NODEBUGdisables Debugging Mode

/NUMPROC=nsets maximum number ofprocessors on multiprocessor machine thatO/S may use

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Switches (con.):

/SAFEBOOT:MINIMALboots to Safe Mode

/SAFEBOOT:NETWORKboots to SafeMode with Networking

/SAFEBOOT:MINIMAL(ALTERNATESHELL)boots to Safe Mode with Command

Prompt/SOSdisplays device driver names when

they are loaded

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Advanced RISC Computing

Pathnames (Page 1)

Advanced RISC Computing pathnameis a path naming convention that is usedin the "Boot.ini" file

Defines the hard disk, partition and folderwhere Windows XP Professional and anyother operating systems reside

Created automatically when an operatingsystem is installed into a partition

To Sample"Boot.ini"

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Advanced RISC Computing

Pathnames (Page 2)

The parts of the path are:

scsi(n) or multi(n)whether the drive typeis SCSI or other (multi) and the adapter

number

disk(n)the SCSI bus number

rdisk(n)which disk contains the O/S

partition(n)selects partition with the O/S\pathselect path with the O/S

To Sample"Boot.ini"

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Editing Boot.ini

Options for editing (see next slides):

Use Control Panel to edit indirectly

Use text editor (i.e. Notepad) to changethe Boot.ini file directly

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Using Control Panel

Safest way to proceed

Select System applet in "Control Panel",then select Advanced tab, and the Startupand Recovery button

Options to modify:

Choose "Default operating system" (the

default boot selection) Select "Time to display list of operating

systems" (delay interval before bootselection starts automatically)

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Startup and Recover Dialog

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Using a Text Editor

Use Notepad or any other text editor

The button in the "Startup andRecovery" window launches Notepad

and opens the Boot.ini file

Be careful when editing file

Windows XP might not boot if there is an

incorrect configuration Create backup copy of the file before

making changes

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*** Activity ***

Before starting this activity, you shouldbackup boot.ini

Modify "timeout" value using Notepad

Set the "timeout" value back to its originalvalue (30) using Startup and Recoverydialog in System applet in "Control Panel"

Return to Notepad and open boot.ini toconfirm the change

S t lid

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*** Activity ***

Before starting this activity, you shouldbackup boot.ini

In Notepad, create one or more additionaloperating system entries, i.e.

An additional Windows XP Professionalentry but booting in VGA Mode

A fictionalentry for Windows 2000 on analternate partition

See next slide

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Sample "Boot.ini"

[boot loader]

timeout=30

default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS

[operating systems]

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="MicrosoftWindows XP Professional" /fastdetect

multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft

Windows XP Pro VGA Mode" /fastdetect/basevideo

multi(0)disk(0)rdisk(3)partition(2)\WINNT="MicrosoftWindows 2000" /fastdetect

To Sample"Boot.ini"

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Windows XP Load Phase

Stages:

Loading the kernel

Initializing the kernel

Services load

Windows XP system startup

Logging on

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Loading the Kernel (Page 1)

Once Windows XP is selected as O/S toboot, a "Starting Windows" text message

and the XP splash screen are displayed

During this time the boot loader loads thekernel into memory (consists of):

Windows XP kernel (Ntoskrnl.exe)

Hardware abstraction layer (HAL), the filethat is named Hal.dll

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The kernel is the centralmodule of an operating system:

Loads first and remains in

main memory at all times

Essential that it is as small aspossible while still providingservices required by the O/Sand applications

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The kernel (con.)

Communicates between processes andthe hardware

Responsible for memory management,

process and task management, and diskmanagement

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The Hardware Abstraction Layer (HAL)is an O/S programming component

Functions as an interface between the

systems hardware and software

Applications do not access hardwaredirectly but access the abstract layerprovided by the HAL

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Hardware Abstraction Layer (con.):

Like APIs, allows applications to be device-independent

They abstract information from systemssuch as caches, I/O buses and interrupts

Use this data to give the software a way tointeract with the specific requirementsof

the hardware on which it is running

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Before kernel and HAL begin to execute,the boot loader loads the Registry keyHKLM\SYSTEM

Retrieves configuration based upon Registrysubkey HKLM\SYSTEM\Select data value

CurrentControlSet is created (not written toRegistry yet) from one of the following:

ControlSet00x, a per either the Select orLastKnownGoodRecovery(if Last KnownGood Configuration was selected) data

value, Default, etc.

See next slide (HKLM\SYSTEM\Select)

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Loading the Kernel

Return

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Loads driverslisted in Registry subkey:

HKLM\SYSTEM\CurrentControlSet\Services

These drivers are loaded and/or initializedaccording to their Registry settings

See next slide (HKLM\SYSTEM\CurrentControlSet\Services

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Initializing the Kernel (Page 1)

Registry key HKLM\HARDWARE createdby kernel using information it receivedfrom boot loader program Ntdetect.com

Creates CloneControlSet by making acopy of CurrentControlSet

Never modifiedintended as a backup

Initializes drivers that were loaded by theboot loader

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If the driver experiences an error whileloading, a message with the error levelreported is reported to the kernel:

Ignoreerror is ignored and no message isdisplayed to user

Normalboot process continues withmessage displayed to user

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Driver error levels (con.):

Severedisplays message; if Last KnownGood Configuration is not in use, restarts

using LKGC; if LKGC is in use, bootprocess continuesafter message

Criticaldisplays message; if Last KnownGood Configuration is not in use, restarts

using LKGC; if LKGC is in use, bootprocess failsafter message

All events saved to the System log

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Services Load (Page 1)

Kernel starts Session Manager

Starts programs that correspond to keyentries under Registry key:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute

A REG_MULTI_SZ data type, i.e. an array

The default entry Autocheck makes surethese files are consistent, and tries torepair them if they are not

See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\BootExecute

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Services Load

Return

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Paging files are set up as per:

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\Memory Management

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Services Load

Return

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Session Manager writes to Registry:

CurrentControlSet

CloneControlSet

Windows (Win32) subsystem loaded asper Registry entry:

HKLM\SYSTEM\CurrentControlSet\Control\

Session Manager\Subsystems Default subsystem, and also the subsystem

in which the user shell always executes

See next slide (HKLM\SYSTEM\CurrentControlSet\Control\SessionManager\Subsystems

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Services Load

Return

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Windows XP System Startup

At this point, Windows is considered fullystarted which is signaled by appearance ofa Windows XP logon screen

Win32 subsystem starts winlogon.exewhich launches Local Security Authority(Lsass.exe) process

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Logging On

The user logs on successfully with logonname, as well as a password if required

Clone control set is copied to the Last

Known Good control set completing theboot process

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Multiple-boot Systems (Page 1)

Windows XP operating system can coexistpeacefully with other operating systems

Operating system uses one or more file

systems to organize the data withinvolumes, i.e. FAT or NTFS

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Not all file systems and operating systemsare compatible:

MS-DOS, Windows 95/98, Windows NT,

Windows 2000, Windows Server 2003 andWindows XP can share files through FATvolumes

Windows NT, Windows 2000, Windows

Server 2003 and Windows XP can sharefiles through NTFS volumes

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File system and operating systemcompatibility (con.):

Windows and UNIX do not have a common

file system, but Linux can access FATvolumes

Only Windows 2000, Windows Server 2003and Windows XP support dynamic disks

When selecting file systems for partitionsin a multiple-boot system, keep thesefactors in mind if you wish to share files

between the partitions

Multiple Windows Operating

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Systems (Page 1)

Different versions of Windows can beinstalled on the same system, i.e.

Windows 3.1, Windows 3.11, Windows

95/98, Windows NT, Windows 2000,Windows Server 2003, even Linux/Unix

Even the same version of Windows XPcan be installed on separate partitions


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Systems (Page 2)

Why? User needs to run software versionsthat require an older O/S

Just remember to specify different partitions

for each installation

To run an application under two O/Ss, run

the setup program twice, once while booted

to each operating system

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Multiple Installation Order

Order in which you install operatingsystems is important

Install older operating systems first, i.e.

MS-DOS, Windows 95/98, Windows2000/2003, etc.

This really is a warning, not necessarily an

absolute requirement When installing Windows XP, it recognizes

the previously installed older O/S andleaves it alone

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xp booting

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