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Chapter 2.5. The Boot Process > Understanding boot.ini - Pg. 100

The Boot Process 100 Kernel Phase The Kernel phase consists of two separate tasks: one responsible for driver loading and one for driver initialization. Typically, a boot failure will occur during the initialization phase. · Kernel load.The Kernel phase begins when ntoskrnl.exe takes control. The hardware abstrac- tion layer (HAL), which masks platform- specific hardware differences from Windows 2000, is loaded immediately after the Kernel. The Registry SYSTEM hive is loaded and scanned for drivers and services that are marked to be loaded at this stage. Drivers and services are pro- cessed in groups that are enumerated in the ServiceGroupOrder subkey of HKEY_LOCAL_MA- CHINE\ SYSTEM\CurrentControlSet\Control. This portion of the boot process is displayed for users as a progress bar across the bottom of the screen. The actual drivers and services can be displayed by adding /SOS to the appropriate OS line of boot.ini. For more information , see "Troubleshooting the Boot Process" later in this chapter . · Kernel initialization.Drivers loaded during the load phase are initialized and the SYSTEM hive is once again scanned for high-level drivers that should be loaded. The CurrentControlSet and the Clone hives are created and initialized, but not saved. In the final stage of Kernel initialization, the hardware list compiled by Ntdetect.com is stored in the Registry under HKEY_LOCAL_MA- CHINE\HARDWARE. Services Phase Session Manager (Smss.exe) begins to load the higher-order services and subsystems, including memory management and subsystems. Session Manager executes the instructions listed in Boot- Execute under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ Session Manager. The default entries include instructions to autocheck all drives and to initialize the DFS file system under Windows 2000 Server. For more information on the Distributed File System, see "Hierarchical Storage Management" in Chapter 5.2, "File Systems and Disks." After the volumes have been checked, Session Manager scans the Registry for paging file infor- mation, creates the paging file(s), and writes the CurrentControlSet and Clone control set. The final task of the Session Manager is to load the subsystems specified in HKEY_LOCAL_MA- CHINE\SYSTEM\CurrentControlSet\ Control\SubSystems\Session Manager\Required. Windows 2000 Subsystem Initialization By default, the only subsystem started by Session Manager is the Win32 subsystem (Csrss.exe). Other subsystems such as OS2 and POSIX do not load until a corresponding application is launched. Logon Phase When the Win32 subsystem initializes, Winlogon.exe is started, which in turn starts the Local Se- curity Authority subsystem (Lsass.exe) and the Welcome to Windows dialog box (Press Ctrl+Alt +Del to begin). By providing a valid set of credentials, (user account and password), the individual logging onto the server is verifying that this was a good boot of the operating system. After the user's credentials are validated, the Clone control set is copied to the LastKnownGood control set and the boot is considered complete. Understanding boot.ini The purpose of the boot.ini file is to provide a list of operating systems and OS modifiers installed on the system, the location of the load files for those operating systems, and information about the default OS and how to start it.