Operating Systems Domains

OS Instalation & Configuration part 3


2.3 Identify the basic system boot sequences and boot methods, including the steps to create an emergency boot disk with utilities installed for Windows 9x, Windows NT, and Windows 2000.

Startup Process Windows 95/98

ROM BIOS Bootstrap Process

  • POST Power On Self Test routines are run.
  • The master boot record and partition table are read.
  • The Plug and Play BIOS checks nonvolatile random access memory (RAM) for input/output (I/O) port addresses, interrupt request lines (IRQs), direct memory access (DMA) channels, and other settings needed to configure Plug and Play devices on the computer.
  • All Plug and Play devices found by the Plug and Play BIOS are disabled.
  • A map of used and unused resources is created.
  • The Plug and Play devices are configured and re-enabled, one at a time.
  • If your computer does not have a Plug and Play BIOS, Plug and Play devices are initialized using their default settings when you start your computer.

    Master Boot Record and Boot Sector

  • The master boot record (MBR) locates the boot partition by reading the partition table located at the end of the master boot record.
  • The MBR then passes control to the boot sector in that partition, which contains the disk boot program.
  • The boot sector copies the Io.sys file from the root directory into memory.
  • Io.sys File
  • Minifile allocation table (FAT) file system is loaded.
  • Msdos.sys file is read.
  • Starting Windows 95 message is displayed.
  • If you have multiple hardware profiles in Windows 95, you must choose a hardware configuration to use now.
  • Logo.sys file is loaded and displays a startup image on the screen.
  • If the Drvspace.ini or Dblspace.ini file exists, the Drvspace.bin or Dblspace.bin file is loaded into memory.
  • Io.sys file checks the system registry files.
  • Io.sys file opens the System.dat file.
  • The Dblbuff.sys file is loaded if double buffering is enabled.
  • If you have multiple hardware profiles in Windows 95, the hardware profile you selected earlier is loaded from the registry.
  • Io.sys file processes the Config.sys file.
  • Real-Mode Configuration

    Some hardware devices and programs require that drivers or files be loaded in real-mode in order for them to work properly. Config and Autoexec are only need for backward compatibility.

  • Config.sys file loads drivers into memory. If the Config.sys file does not exist, the Io.sys file loads the following required drivers: Ifshlp.sys, Himem.sys, and Setver.exe
  • Windows 95 reserves all global upper memory blocks (UMBs) for Windows 95 operating system use or for expanded memory support (EMS).
  • Autoexec.bat file loads files and terminate and stay resident (TSR) programs into memory.
  • Win.com File and the Windows 95 Environment
  • Win.com file is run.
  • Win.com file accesses the Vmm32.vxd file and loads into memory.
  • The real-mode virtual device driver loader checks for duplicate virtual device drivers (VxDs) in the Windows\System\Vmm32 folder and the Vmm32.vxd file. If a VxD exists in both the Windows\System\Vmm32 folder and the Vmm32.vxd file, the duplicate VxD is "marked" in the Vmm32.vxd file so that it is not loaded.
  • The real-mode virtual device driver loader checks that all required VxDs loaded successfully. If not, it attempts to load the drivers again.
  • Once the real-mode virtual device driver loading is logged, driver initialization occurs. If there are any VxDs that require real-mode initialization, they begin their process in real-mode.
  • Vmm32 switches the computer's processor from real-mode to protected- mode.
  • VxD initialization process occurs.
  • After all the static VxDs are loaded, the Krnl32.dll, Gdi.exe, User.exe, and Explorer.exe files are loaded.
  • Network Environment and Multi-User Profiles
  • The network environment is loaded.
  • User is prompted to log on to the network
  • Programs in the Startup group and the RunOnce registry key are run.
  • After each program in the RunOnce registry key is started, the program is removed from the key.
  • Startup Process Windows NT/2000

    Steps prior to boot sequence

  • POST Power On Self Test routines are run.
  • The boot device is located, and the MBR (Master Boot Record) is loaded into memory, and locates the active partition boot sector, and loads it into memory.
  • From the boot sector NTLDR is loaded into memory.
  • Boot Sequence
  • NTLDR switches the processor from real mode into 32 bit flat memory mode.
  • NTLDR starts the minifile system drivers, either FAT, FAT 32 (2000 only) or NTFS.
  • NTLDR reads the BOOT.INI file, and displays the Boot Loader Menu. If you have a dual boot system and choose an OS other than Windows NT NTLDR will load BOOTSECT.DOS and pass control to it for booting.
  • If Windows NT/2000 is selected, NTLDR will run NTDETECT.COM which scans the computers hardware and passes this information back to NTLDR.
  • NTLDR then loads NTOSKRNL.EXE, HALL.DLL, and the SYSTEM hive.
  • Kernel Load Phase
  • The HAL (hardware abstraction layer) is loaded, which hides the physical hardware from applications.
  • The SYSTEM hive, is loaded and scanned for device drivers, and services that should be loaded. These are organized into groups They are loaded into memory but not initialized yet, in the order in which they appear in the ServiceGroupOrder subkey of the registry.
  • Kernel Initialization Phase

    In this phase the screen is blue, and initializes the kernel and the drivers that were loaded during the kernel load phase.

  • The kernel is initialized.
  • SYSTEM hive is scanned again to determine which drivers should be loaded, then they are initialized.
  • Services Load Phase

    The services load phase starts the Session Manager SMSS.EXE. It will run the programs listed in its BootExecute Registry entry, as well as starting the required subsystems.

    Win 32 Subsystem Start Phase

    When the 32 Subsystem Starts it automatically starts WINLOGON.EXE which starts the Local Security Authority LSASS.EXE and displays Ctrl+Alt+Delete logon dialog.

    Next the The Service Controller (Screg.exe) will check the Registry for services that are marked to load automatically and will load them.

    User Logon

    The Boot is not considered good until a user logs on successfully

    Startup disk

    You can create a start up disk during set up, or later by opening Add/Remove Programs in control panel, select Start Disk tab in both Windows 95/98.

    Windows 95 Startup Disk

    Files that are copied to the Windows 95 Startup Disk

  • attrib.exe File attribute utility
  • command.com Core operating system file
  • drvspace.bin Disk compression utility
  • ebd.sys Utility for the startup disk
  • edit.com Text editor
  • fdisk.exe Disk partition utility
  • format.com Disk format utility
  • io.sys Core operating system file
  • msdos.sys Core operating system file
  • regedit.exe Real-mode Registry Editor
  • scandisk.exe Disk status and repair utility
  • scandisk.ini Disk status utility configuration file
  • sys.com System transfer utility
  • Windows 98 Startup Disk

    You can also create the disk from the DOS command line.

  • cd windows\command
  • bootdisk a:
  • Startup disks created with previous versions of Windows are not compatible with Windows 98.

    The following items have been added to the Windows 98 Startup Disk, that were not included on Windows 95 Startup Disk.

  • Startup Menu
  • Real-Mode IDE CD-ROM support
  • Real-Mode SCSI CD-ROM support
  • Edb.cab file
  • RAMDrive
  • New extract command: Ext.exe
  • Contents of the Windows 98 Startup Disk
  • Aspi2dos.sys Real-mode Adaptec CD-ROM driver.
  • Aspi4dos.sys Real-mode Adaptec CD-ROM driver.
  • Aspi8dos.sys Real-mode Adaptec CD-ROM driver.
  • Aspi8u2dos.sys Real-mode Adaptec CD-ROM driver.
  • Aspicd.sys Real-mode Adaptec CD-ROM driver.
  • Autoexec.bat
  • Btcdrom.sys Mylex/BusLogic CD-ROM driver.
  • Btdosm.sys Mylex/BusLogic CD-ROM driver.
  • Command.com
  • Config.sys Loads the device drivers.
  • Edb.cab Cabinet file containing extract utilities.
  • Ebd.sys A file that identifies the disk as a Windows 98 startup disk.
  • Extract to expand the Ebd.cab file.
  • Fdisk.exe Disk partition tool.
  • Findramd.exe Utility to find the RAM drive during startup.
  • Flashpt.sys Mylex/BusLogic CD-ROM driver.
  • Himem.sys XMS Memory Manager.
  • Io.sys System boot file.
  • Msdos.sys Boot option information.
  • Mode.com Lets you change display parameters such as number columns.
  • Oakcdrom.sys Generic device driver for ATAPI CD-ROM drives.
  • Ramdrive.sys Creates a Ramdrive during startup.
  • Readme.txt
  • Setramd.bat Searches for first available drive to be a Ramdrive.
  • Sys.com System transfer tool.
  • The Edb.cab file contains several utilities
  • Attrib.exe Add or remove file attributes.
  • Chkdsk.exe Simpler and smaller disk status tool.
  • Debug.exe Debug utility.
  • Edit.com Real-mode emergency text editor.
  • Ext.exe File extract utility.
  • Format.com Disk format tool.
  • Help.bat Launches the readme.txt for the startup disk.
  • Help.txt Text document with information for troubleshooting Windows 98 when it fails to set up correctly, third-party disk partitioning software, and diagnostic tools.
  • Mscdex.exe Microsoft CD-ROM file extension for MS-DOS.
  • Restart.com Restart your computer.
  • Scandisk.exe Disk status tool.
  • Scandisk.ini Disk status tool configuration file.
  • Sys.com System transfer tool.
  • Uninstal.exe Tool for removing Windows 98
  • Windows NT

    To create setup disks

    You will need four blank, formatted, 1.44-MB floppy disks. Label them Setup Disk One, Setup Disk Two, and Setup Boot Disk.

  • Insert disk into the floppy disk drive
  • Insert the Windows NT CD-ROM into the CD-ROM drive
  • From Windows 9x click Start, and then click Run
  • Type cd drive:\i386\winnt /ox
  • From Windows NT click Start, Type cd drive:\i386\winnt /ox
  • Follow the screen prompts
  • Windows 2000

    To create setup disks

    You will need four blank, formatted, 1.44-MB floppy disks. Label them Setup Disk One, Setup Disk Two, Setup Disk Three, and Setup Disk Four

  • Insert disk into the floppy disk drive
  • Insert the Windows 2000 CD-ROM
  • Click Start, and then click Run
  • Type d:\bootdisk\makeboot a:
  • Follow the screen prompts
  • You can also create these setup disks from the DOS command line.

    Safe Mode

    Windows automatically initiates Safe Mode if it detects that system startup failed , or if the registry is corrupted.

    Safe Mode bypasses startup files, including the registry, Config.sys, Autoexec.bat, and the [Boot] and [386Enh] sections of System.ini, and provides you with access to the Windows configuration files. You can make any necessary configuration changes, and then restart Windows normally.

    Windows in Safe Mode, only the mouse, keyboard, and standard VGA device drivers are loaded.

    Safe Mode With Networking is not supported in Windows 98.

    Safe Mode Command Prompt Only loads the Command.com and DoubleSpace or DriveSpace files (if present). It does not load Himem.sys, Ifshlp.sys, or Windows .

    Step-by-Step Confirmation allows you to specify which commands and drivers the system should process by confirming each line of the startup files.

    Safe Mode and Windows 2000


  • Safe Mode - Starts Windows 2000 using only basic files and drivers (mouse, except serial mice; monitor; keyboard; mass storage; base video; default system services; and no network connections).
  • Safe mode with Networking - Starts Windows 2000 using only basic files and drivers, plus network connections.
  • Safe Mode with Command Prompt - Starts Windows 2000 using only basic files and drivers. After logging on, the command prompt is displayed instead of the Windows desktop.
  • Enable Boot Logging - Starts Windows 2000 while logging all the drivers and services that were loaded (or not loaded) by the system to a file. This file is called ntbtlog.txt and it is located in the windir directory. Safe Mode, Safe Mode with Networking, and Safe Mode with Command Prompt add to the boot log a list of all the drivers and services that are loaded. The boot log is useful in determining the exact cause of system startup problems.
  • Enable VGA Mode - Starts Windows 2000 using the basic VGA driver. The basic video driver is always used when you start Windows 2000 in Safe Mode (either Safe Mode, Safe Mode with Networking, or Safe Mode with Command Prompt).
  • Last Known Good Configuration - Starts Windows 2000 using the registry information that Windows saved at the last shutdown. Use only in cases of incorrect configuration. Last known good configuration does not solve problems caused by corrupted or missing drivers or files. Also, any changes made since the last successful startup will be lost.
  • Debugging Mode - Starts Windows 2000 while sending debug information through a serial cable to another computer.
  • MS-DOS mode

    Order of execution for MS-DOS:

  • IO.SYS
  • NTLDR (NT Loader), BOOT.INI

    Ntldr is the operating system loader. Ntldr must be in the root directory. Boot.ini is the file that Ntldr reads in order to know what options and timeout to present.

    Ntldr reads the boot.in file, and displays the the operating systems Boot Menu. If Windows NT/2000 is selected, NTLDR will run NTDETECT.COM.  If another OS is selected, NTLDR will load and run BOOTSECT.DOS, and pass control to it.

    Boot.ini is a hidden, read-only text file stored in the root of the system partition.There are two sections to the boot.ini, boot loader section and operating systems section.

    The boot loader section contains two parts.

    • timeout = number
      • The number following timeout is the seconds that the boot menu will display before starting the boot proccess. The default is 30.
      • default = option
        • After a time out, this option tells Ntldr which of the menu items to use to continue booting
      • operating systems section contains a list of operating systems to boot. Which includes the path and a description for the OS's.

      Files required to boot

      Windows 95/98

    IO.SYS - The real-mode operating system, VMM32 and Windows 9x device drivers take control from Io.sys. 
    MSDOS.SYS - contains special information for Windows 98, and for compatibility with applications that require Msdos.sys. to be present. 
    CONFIG.SYS - is not required for Windows 9x, but it is included for compatibility.
    AUTOEXEC.BAT - is not required for Windows 95 or Windows 98, but it is included for compatibility.
    Windows NT/2000
    NTLDR - Hidden, read only system file loads the operating system.
    Root of the active partition
    Boot.ini - Read only system file, used to build the the boot menu.
    Root of the active partition
    Bootsect.dos - Hidden system file loaded by NTLDR only if dual booting, another OS. 
    Root of the active partition
    Ntdetect.com - Hidden, read only system file used to build a hardware list and pass the information back to NTLDR to be added to the registry latter in the boot process.
    Root of the active partition
    Ntbootdd.sys - (only if booting from a SCSI partition, and SCSI BIOS is not present on the controller)
    Root of the active partition
    Ntoskrnl.exe - This the Kernel file.
    SYSTEM - Controls which drivers and services are loaded.
    Device drivers - These are files that support various device drivers.
    Creating emergency repair disk (ERD)

    Windows 2000

  • Open Backup
  • On the Tools menu, click Create an Emergency Repair Disk
  • Follow the instructions that appear on your screen
  • To restore your settings from the ERD, you need your Windows 2000 CD, the Windows 2000 Setup disks, and the ERD. During the restoration process.

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