What is the NT Boot Process?

A. A. Firstly the files required for NT to boot are

  • Ntldr - This is a hidden, read-only system file that loads the operating system
  • Boot.ini - This is read-only system file, used to build the Boot Loader Operating System Selection menu on Intel x86-based computers
  • Bootsect.dos - This is a hidden file loaded by Ntldr if another operating system is selected
  • Ntdetect.com - This is a hidden, read-only system file used to examine the hardware available and to build a hardware list.
  • Ntbootdd.sys - This file is only used by systems that boot from a SCSI disk.

The common Boot sequence files are

  • Ntoskrnl.exe - The Windows NT kernel
  • System - This file is a collection of system configuration settings
  • Device drivers - These are files that support various device drivers
  • Hal.dll - Hardware Abstraction Layer software

The boot sequence is as follows

  1. Power on self test (POST) routines are run
  2. Master Boot Record is loaded into memory, and the program is run
  3. The Boot Sector from Active Partition is Loaded into Memory
  4. Ntldr is loaded and initialized from the boot sector
  5. Change the processor from real mode to 32-bit flat memory mode
  6. Ntldr starts the appropriate minifile system drivers. Minifile system drivers are built into Ntldr and can read FAT or NTFS
  7. Ntldr reads the Boot.ini file
  8. Ntldr loads the operating system selected, on of two things happen
    * If Windows NT is selected, Ntldr runs Ntdetect.com
    * For other operating system, Ntldr loads and runs Bootsect.dos and passes control to it. The Windows NT process ends here
  9. Ntdetect.com scans the computer hardware and sends the list to Ntldr for inclusion in HKEY_LOCAL_MACHINE\HARDWARE
  10. Ntldr then loads Ntoskrnl.exe, Hal.dll and the system hive
  11. Ntldr scans the System hive and loads the device drivers configured to start at boot time
  12. Ntldr passes control to Ntoskrnl.exe, at which point the boot process ends and the load phases begin

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