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Windows XP Boot Process

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Presentation on theme: "Windows XP Boot Process"— Presentation transcript:

1 Windows XP Boot Process
70-270: MCSE Guide to Microsoft Windows XP Professional

2 Booting Windows XP (Page 1)
Boot process phases: Boot phase begins when computer is first powered 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

3 Booting Windows XP (Page 2)
Boot Phase Steps Power-on self test (POST) Initial startup Boot loader Select operating system Detect hardware Select configuration Windows XP Load Phase Load the kernel Initialize the kernel Services load Windows XP system startup Log on

4 Power-on Self Test (Page 1)
First step in boot sequence (the POST) for any computer with an operating system Determines: Amount of real memory that exists Whether or not all necessary hardware components are present and functioning The specific tests vary depending on how the BIOS (Basic Input/Output System) is configured

5 Power-on Self Test (Page 2)
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 error—differs from one BIOS to another) Also possibly might display error message and a code on the screen

6 Power-on Self Test (Page 3)
Software that performs POST resides in called the CMOS (complementary metal oxide semiconductor) Battery-powered chip that also can hold basic configuration information so POST can check installed RAM, number and type of hard drives, type of keyboard and mouse, the boot sequence (Which drive first?), etc. In Windows XP, BIOS no longer stores information about devices and drivers connected to system (replaced by the HAL)

7 Power-on Self Test The following screen shows results of sample successful POST completion

8 Power-on Self Test

9 Power-on Self Test (Page 4)
After POST completes, each adapter with a 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 than standard parallel and serial ports; used for printers, scanners, etc. Adapters issue their own reports on monitor

10 Power-on Self Test (Page 5)
At this point there still is no operating system in RAM … POST application in the BIOS is in control Output on screen is in basic, text-only form

11 Initial Startup (Page 1)
The BIOS finds the first sector of the first hard drive which contains the Master Boot Record (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 to it (either directly or indirectly)

12 Initial Startup (Page 2)
The Master Boot Record (con.): In FAT partitions, because the boot sector is only one sector in size, MBR points to another location on disk which then points to the boot loader In NTFS partitions, boot sectors may be up to 16 sectors in size so it is large enough to store the code to find the boot loader If booting from a floppy, the first sector contains the partition boot sector

13 Initial Startup (Page 3)
BIOS stores information as to the order in which drives are checked to see which is the startup drive (as stored in CMOS) If floppy drive is in the sequence, partition boot sector is loaded and runs the MBR from the floppy If the floppy does not have a partition boot sector, the message "Non-system disk or disk error …" appears Remove disk, and turn machine off an then on—do not reboot to avoid viruses

14 Initial Startup (Page 3)
Ntldr is stored on the system partition This is the partition where the MBR expects to find the system Ultimately its job is to boot the Windows XP operating system which is stored on the boot partition The system itself actually can be stored on any partition The system and boot partitions may or may not be the same

15 Boot Loader (Page 1) Collection of files on system partition used to initiate loading of operating system Required files to boot Windows XP are Ntldr, and Boot.ini Other optional boot loader programs are Bootsect.dos and Ntbootdd.sys

16 Windows XP Startup Files

17 Boot Loader (Page 2) The boot loader first switches processor into 32-bit mode Previously it had been running in real mode as 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 systems is programmed into Ntldr

18 Boot Loader (Page 3) Primary functions of the boot loader are to:
Select the operating system to load if there is more than one from which to choose Detect hardware Select a configuration Ntldr stays in control throughout boot loader process until it loads and passes control to Windows XP kernel (Ntoskrnl.ext)

19 Selecting the Operating System
Ntldr reads Boot.ini and displays the Boot selection menu (if necessary) Contains operating system choices, if more that one, from which the user may choose It also is possible from this screen to press <F8> 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

20 Boot Selection Menu

21 Detecting Hardware If the user selects Windows XP (or if it is the only O/S present), Ntldr executes Used to collect a list of hardware currently installed in computer From hardware list, creates system profile Later will be compared to Windows XP Registry entries for discrepancies that could lead to problems

22 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

23 Troubleshooting and Advanced Startup Options (Page 1)
Windows XP combines the boot and recovery options of Windows NT and Windows 95/98 Provides several options to restore a malfunctioning system to functional state Before timer expires, or Windows XP kernel starts to load, press <F8> to access Windows Advanced Options Menu

24 Troubleshooting and Advanced Startup Options

25 Troubleshooting and Advanced Startup Options (Page 2)
Contents of menu may include: Safe Mode—boots Windows XP with only minimum system files and drivers May be able to boot into a functioning system when some drivers are corrupted Might allow replacing or removing the problem driver before rebooting Safe Mode with Networking—same as above but with networking components If network drivers are not the problem

26 Troubleshooting and Advanced Startup Options (Page 3)
Contents of menu may include (con.): Safe Mode with Command Prompt—same as above but not to the GUI environment Enable Boot Logging—enables or disables boot process, and writes details to log file Ntbtlog.txt in %systemroot% folder Records process of steps between boot menu and logon prompt which could provide clues to which driver, system or procedure is causing the problem

27 Troubleshooting and Advanced Startup Options (Page 4)
Contents of menu may include (con.): Enable VGA Mode—normal boot but with only basic VGA video driver (in case there is a bad video driver) Last Known Good Configuration—state of Registry during last successful user logon Could be useful if a new driver or software recently has been installed, or the Registry was recently modified

28 Troubleshooting and Advanced Startup Options (Page 5)
Contents of menu may include (con.): Directory Services Restore Mode—only on Windows XP domain controllers, restores Active Directory

29 Troubleshooting and Advanced Startup Options (Page 6)
Contents of menu may include (con.): Debugging Mode—normal boot but sends debugging information to another system over a serial cable If no other option helps in restoring system, may help determine where in boot process the problem occurs Complex information usually used by high-end programmers—consult Microsoft Windows XP Professional Resource Kit

30 *** Activity *** Try one or more of following boot options (press <F8> function key during boot): Safe Mode Safe Mode with Command Prompt Enable VGA Mode Last Known Good Configuration Reboot normally when done

31 Boot Configuration and Selecting an Operating System (Page 1)
Controlled through configuration of the Boot.ini file … Located in the root directory of the system partition (usually drive C:\) To view the file, uncheck "Hide Protected operating system files" in Folder Options Updated from the "System and Recovery" dialog window on the Advanced tab of Control Panel's System applet To Sample"Boot.ini"

32 Boot Configuration and Selecting an Operating System (Page 2)
Used by boot loader to display the list of available operating systems Consists of two sections: [boot loader] and [operating systems] To Sample"Boot.ini"

33 Sample "Boot.ini" Return

34 [boot loader] Settings: Default—shows path to default O/S
Timeout—number of seconds system waits for 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 editor—an invalid value in System applet in "Control Panel" Default—shows path to default O/S To Sample"Boot.ini"

35 [operating systems] (Page 1)
Lists available operating systems as follows: Path to boot partition for operating system Text displayed in boot loader screen Optional parameters (switches) provide options many of which are equivalent to <F8> "Windows Advanced Options Menus" As well as a few other options To Sample"Boot.ini"

36 [operating systems] (Page 2)
Switches: /BASEVIDEO—same as Enable VGA Mode /BAUDRATE=n—baud rate for Debugging Mode /BOOTLOG—same as Enable Boot Logging /CRASHDEBUG—starts Debugging Mode but remains inactive until STOP error occurs

37 [operating systems] (Page 3)
Switches (con.): /DEBUG—starts Debugging Mode and allows access by the remote computer /DEBUGPORT={com1|com2|1394}—sets port for Debugging Mode /FASTDETECT={com1|com2|…}—specifies serial ports to skip during hardware scan All if no port specified Included in every entry by default when the operating system is installed

38 [operating systems] (Page 4)
Switches (con.): /MAXMEM=n—sets maximum RAM O/S can use /NOGUIBOOT—boots without showing splash screen /NODEBUG—disables Debugging Mode /NUMPROC=n—sets maximum number of processors on multiprocessor machine that O/S may use

39 [operating systems] (Page 5)
Switches (con.): /SAFEBOOT:MINIMAL—boots to Safe Mode /SAFEBOOT:NETWORK—boots to Safe Mode with Networking /SAFEBOOT:MINIMAL(ALTERNATESHELL)—boots to Safe Mode with Command Prompt /SOS—displays device driver names when they are loaded

40 Advanced RISC Computing Pathnames (Page 1)
Advanced RISC Computing pathname is a path naming convention that is used in the "Boot.ini" file Defines the hard disk, partition and folder where Windows XP Professional and any other operating systems reside Created automatically when an operating system is installed into a partition To Sample"Boot.ini"

41 Advanced RISC Computing Pathnames (Page 2)
The parts of the path are: scsi(n) or multi(n)—whether the drive type is 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 \path—select path with the O/S To Sample"Boot.ini"

42 Editing Boot.ini Options for editing (see next slides):
Use Control Panel to edit indirectly Use text editor (i.e. Notepad) to change the Boot.ini file directly

43 Using Control Panel Safest way to proceed
Select System applet in "Control Panel", then select Advanced tab, and the Startup and Recovery <Settings> button Options to modify: Choose "Default operating system" (the default boot selection) Select "Time to display list of operating systems" (delay interval before boot selection starts automatically)

44 Startup and Recover Dialog

45 Using a Text Editor Use Notepad or any other text editor
The <Edit> button in the "Startup and Recovery" 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

46 *** Activity *** Before starting this activity, you should backup boot.ini Modify "timeout" value using Notepad Set the "timeout" value back to its original value (30) using Startup and Recovery dialog in System applet in "Control Panel" Return to Notepad and open boot.ini to confirm the change

47 *** Activity *** See next slide Before starting this activity, you should backup boot.ini In Notepad, create one or more additional operating system entries, i.e. An additional Windows XP Professional entry but booting in VGA Mode A fictional entry for Windows 2000 on an alternate partition

48 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="Microsoft Windows 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="Microsoft Windows 2000" /fastdetect To Sample"Boot.ini"

49 Windows XP Load Phase Stages: Loading the kernel
Initializing the kernel Services load Windows XP system startup Logging on

50 Loading the Kernel (Page 1)
Once Windows XP is selected as O/S to boot, a "Starting Windows…" text message and the XP splash screen are displayed During this time the boot loader loads the kernel into memory (consists of): Windows XP kernel (Ntoskrnl.exe) Hardware abstraction layer (HAL), the file that is named Hal.dll

51 Loading the Kernel (Page 2)
The kernel is the central module of an operating system: Loads first and remains in main memory at all times Essential that it is as small as possible while still providing services required by the O/S and applications

52 Loading the Kernel (Page 3)
The kernel (con.) Communicates between processes and the hardware Responsible for memory management, process and task management, and disk management

53 Loading the Kernel (Page 4)
The Hardware Abstraction Layer (HAL) is an O/S programming component Functions as an interface between the system’s hardware and software Applications do not access hardware directly but access the abstract layer provided by the HAL

54 Loading the Kernel (Page 5)
Hardware Abstraction Layer (con.): Like APIs, allows applications to be device-independent They abstract information from systems such as caches, I/O buses and interrupts Use this data to give the software a way to interact with the specific requirements of the hardware on which it is running

55 Loading the Kernel (Page 6)
Before kernel and HAL begin to execute, the boot loader loads the Registry key HKLM\SYSTEM … Retrieves configuration based upon Registry subkey HKLM\SYSTEM\Select data value CurrentControlSet is created (not written to Registry yet) from one of the following: ControlSet00x, a per either the Select or LastKnownGoodRecovery (if “Last Known Good Configuration” was selected) data value, Default, etc. See next slide (HKLM\SYSTEM\Select)

56 Loading the Kernel Return

57 Loading the Kernel (Page 7)
Loads drivers listed in Registry subkey: HKLM\SYSTEM\CurrentControlSet\Services These drivers are loaded and/or initialized according to their Registry settings See next slide (HKLM\SYSTEM\CurrentControlSet\Services

58 Loading the Kernel Return

59 Initializing the Kernel (Page 1)
Registry key HKLM\HARDWARE created by kernel using information it received from boot loader program Creates CloneControlSet by making a copy of CurrentControlSet Never modified—intended as a backup Initializes drivers that were loaded by the boot loader

60 Initializing the Kernel (Page 2)
If the driver experiences an error while loading, a message with the error level reported is reported to the kernel: Ignore—error is ignored and no message is displayed to user Normal—boot process continues with message displayed to user

61 Initializing the Kernel (Page 3)
Driver error levels (con.): Severe—displays message; if Last Known Good Configuration is not in use, restarts using LKGC; if LKGC is in use, boot process continues after message Critical—displays message; if Last Known Good Configuration is not in use, restarts using LKGC; if LKGC is in use, boot process fails after message All events saved to the System log

62 Services Load (Page 1) Kernel starts Session Manager
Starts programs that correspond to key entries 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 sure these files are consistent, and tries to repair them if they are not See next slide (HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\BootExecute

63 Services Load Return

64 Services Load (Page 2) Paging files are set up as per:
HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management See next slide (HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management

65 Services Load Return

66 Services Load (Page 3) Session Manager writes to Registry:
CurrentControlSet CloneControlSet Windows (Win32) subsystem loaded as per 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\Session Manager\Subsystems

67 Services Load Return

68 Windows XP System Startup
At this point, Windows is considered fully started which is signaled by appearance of a Windows XP logon screen Win32 subsystem starts winlogon.exe which launches Local Security Authority (Lsass.exe) process

69 Logging On The user logs on successfully with logon name, as well as a password if required Clone control set is copied to the Last Known Good control set completing the boot process

70 Multiple-boot Systems (Page 1)
Windows XP operating system can coexist peacefully with other operating systems Operating system uses one or more file systems to organize the data within volumes, i.e. FAT or NTFS

71 Multiple-boot Systems (Page 2)
Not all file systems and operating systems are compatible: MS-DOS, Windows 95/98, Windows NT, Windows 2000, Windows Server 2003 and Windows XP can share files through FAT volumes Windows NT, Windows 2000, Windows Server 2003 and Windows XP can share files through NTFS volumes

72 Multiple-boot Systems (Page 3)
File system and operating system compatibility (con.): Windows and UNIX do not have a common file system, but Linux can access FAT volumes Only Windows 2000, Windows Server 2003 and Windows XP support dynamic disks When selecting file systems for partitions in a multiple-boot system, keep these factors in mind if you wish to share files between the partitions

73 Multiple Windows Operating Systems (Page 1)
Different versions of Windows can be installed 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 XP can be installed on separate partitions

74 Multiple Windows Operating Systems (Page 2)
Why? User needs to run software versions that require an older O/S Just remember to specify different partitions for each installation To run an application under two O/S’s, run the setup program twice, once while booted to each operating system

75 Multiple Installation Order
Order in which you install operating systems is important Install older operating systems first, i.e. MS-DOS, Windows 95/98, Windows 2000/2003, etc. This really is a warning, not necessarily an absolute requirement When installing Windows XP, it recognizes the previously installed older O/S and leaves it alone


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