Bootmgr

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BOOTMGR (Boot Manager)
Basic data

developer Microsoft
Current  version see Microsoft Windows
operating system Windows from
Vista / Server 2008
category Boot manager
License Proprietary

BOOTMGR is the boot manager for Windows operating systems from Microsoft from Windows Vista or Windows Server 2008 . He is the successor of the last in Windows XP or Windows Server 2003 used NT Loader (NTLDR).

procedure

When the computer is switched on, the computer's firmware is loaded first, such as the BIOS or the Unified Extensible Firmware Interface (UEFI).

BIOS
In the case of an IBM-PC-compatible computer with BIOS, this reads the master boot record (MBR) on the hard disk or another storage medium and executes it. With a standard MBR, as it has been used almost unchanged by Microsoft since MS-DOS 2.0 in MS-DOS, PC DOS and Windows, the code located there then turns the boot sector in the volume boot record (VBR) into the one marked as active Partition loaded and executed. The code from the boot sector of a partition VBR, a corresponding Windows installation is on, is now able to produce a file bootmgrin the root directory of a NTFS - file system to find and execute. The BOOTMGR program reads the file \Boot\BCDand displays a boot menu for selecting the operating system to be started. The BOOTMGR also checks the disk signature (bytes 440–443 in the MBR) with its saved boot entries from the boot configuration data . If the disk signature was changed, Windows refuses to start with a “ winload error ”.
EFI
If (U) EFI is available, the first two parts from the MBR and VBR are superfluous. The Boot Manager is \EFI\Microsoft\Boot\bootmgfw.efisaved in the file in the EFI system partition and is loaded and executed directly by the firmware. According to the EFI standard, \EFI\BOOT\bootia32.efiwith 32-bit or \EFI\BOOT\bootx64.efi64-bit (U) EFI, which contain the same boot manager after the installation of Windows, if these files were not already available, serve as fallback . The functionality of the EFI bootloader is identical to BOOTMGR.

BOOTMGR starts next winload.efiif Windows is to be loaded. It then loads the HAL , the kernel and its libraries and device drivers just like NTLDR . It also loads the Windows registry . Control then passes to the kernel, which initializes itself and loads further system services. winload.efi

Boot settings

All settings for the bootloader are stored in the file for BIOS \Boot\BCDsystems and in the file \EFI\Microsoft\Boot\BCDin the EFI system partition for EFI systems . The boot configuration data is stored in a binary file and its structure is a hive of the Windows registry . Microsoft provides the command-line tool bcdedit.exeto to change boot parameters. It is also possible to bootrec.execall up the tool when booting from the Windows CD via the item “Repair your computer / System recovery options” . Alternatively, the EasyBCD program from NeoSmart Technologies or the Visual BCD Editor can be used to change the BOOTMGR settings.

The details of the new BCD format are undocumented.

Comparison with the NT loader

BOOTMGR offers configuration options similar to those of the NT loader:

  • Booting Windows Vista or Windows 7 with winload.exe
  • Restore Windows from hibernation usingwinresume.exe
  • Windows NT 5.1 or older versions using NTLDR will start
  • Any VBR or MBR invite
  • Load any images

Differences:

  • The boot settings file in the NT Loader is boot.iniin the main directory and can be edited with a text editor.

Individual evidence

  1. ↑ Multibooters - Dual / Multi Booting With Vista bootmgr and BCD and Disk Signature
  2. ↑ windows-driver-content: BCD System Store Settings for UEFI. Retrieved August 12, 2019 (American English).
  3. ↑ Microsoft: Boot Configuration Data Reference Documentation . In: Microsoft Platform SDK . Archived from the original on March 15, 2008. Retrieved December 14, 2010. (English)
  4. ↑ Jonathan de Boyne Pollard: The Windows NT 6 boot process . In: Frequently Given Answers . Retrieved December 14, 2010.