4-11Lesson 1 Explaining the Startup Process
HKEY_LOCAL_MACHINE\SYSTEM\Select subkey of the Registry. The Clone con-
trol set is never modified because it is intended to be an identical copy of the data
used to configure the computer and should not reflect changes made during the
startup process.
Device drivers are loaded and initialized. After creating the Clone control set, the
kernel initializes the low-level device drivers that were loaded during the kernel
load phase. The kernel then scans the HKEY_LOCAL_MACHINE\ SYSTEM\Cur-
rentControlSet\Services subkey of the Registry for device drivers with a value of
0x1 for the Start entry. As in the kernel load phase, a device driver’s value for the
Group entry specifies the order in which it loads. Device drivers initialize as soon
as they load. If an error occurs while loading and initializing a device driver, the
boot process proceeds based on the value specified in the ErrorControl entry for
the driver. Table 4-4 describes the possible ErrorControl values and the resulting
boot sequence actions.
Table 4-4 ErrorControl Values and Resulting Action
ErrorControl
Value Action
0x0 (Ignore) The boot sequence ignores the error and proceeds without displaying an
error message.
0x1 (Normal) The boot sequence displays an error message, but ignores the error and pro-
ceeds.
0x2 (Severe) The boot sequence fails and then restarts using the Last Known Good control
set. If the boot sequence is currently using the Last Known Good control set,
the boot sequence ignores the error and proceeds.
0x3 (Critical) The boot sequence fails and then restarts using the Last Known Good control
set. However, if the Last Known Good control set is causing the critical error,
the boot sequence stops and displays an error message.
Note ErrorControl values appear in the Registry under the subkey HKEY_LOCAL_MACHINE\
SYSTEM\CurrentControlSet\Services\name_of_service_or_driver\ErrorControl.
Services are started. After the kernel loads and initializes device drivers, Session
Manager (SMSS.EXE) starts the higher-order subsystems and services for Windows
XP Professional. Session Manager executes the instructions in the BootExecute
data item, and in the Memory Management, DOS Devices, and SubSystems keys.
Table 4-5 describes the function of each instruction set and the resulting Session
Manager action.
Table 4-5 Session Manager Reads and Executes These Instruction Sets
Data Item or Key Action
Session Manager executes the commands specified in this data item before
BootExecute
it loads any services.
data item
Session Manager creates the paging file information required by the Virtual
Memory Manage-
Memory Manager.
ment key
DOS Devices key Session Manager creates symbolic links that direct certain classes of com-
mands to the correct component in the file system.
SubSystems key Session Manager starts the Win32 subsystem, which controls all input/out-
put (I/O) and access to the video screen, and starts the WinLogon process.
What Happens During the Logon Phase
The logon phase begins at the conclusion of the kernel initialization phase. The Win32
subsystem automatically starts WINLOGON.EXE, which in turn starts the Local Security
Authority (LSASS.EXE) and displays the Logon dialog box. You can log on at this time,
even though Windows XP Professional might still be initializing network device drivers.
Next, the Service Control Manager executes and makes a final scan of the HKEY_
LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services subkey, looking for services
with a value of 0x2 for the Start entry. These services, including the Workstation service
and the Server service, are marked to load automatically.
The services that load during this phase do so based on their values for the DependOn-
Group or DependOnService entries in the HKEY_LOCAL_MACHINE\ SYSTEM\Cur-
rentControlSet\Services Registry subkey.
A Windows XP Professional startup is not considered good until a user successfully
logs on to the system. After a successful logon, the system copies the Clone control set
to the Last Known Good control set.
Note For more information on Last Known Good configuration, see Lesson 3 later in this
chapter.
Lesson Review
Use the following questions to help determine whether you have learned enough to
move on to the next lesson. If you are unable to answer a question, review the lesson
materials and try the question again. You can find answers to the questions in the
“Questions and Answers” section at the end of this chapter.
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