Booting Files

Boot loader is a piece of code that runs before any operating system is running. They are used to boot other operating systems, usually each operating system has a set of bootloaders specific for it.

Windows Booting Files

• bootmgr : Operating System loader code in Windows Vista and later versions of windows., This file is stored in the System Reserved Partition or the windows installation drive.

• Boot Configuration Database(BCD) : Builds the operating system selection menu in Windows Vista and later versions of Windows. This file is stored in System Reserved Partition\boot\BCD or the windows installation drive.

• winload.exe : Loads Windows Vista and later version of operating system. The file is located in %SystemRoot\system32\winload.exe.

• winresume.exe : Resume the Windows Operating System if system is started from hiberated state. This file is located in %SystemRoot%\system32\winresume.exe.

• ntldr : Operating System loader code in windows XP and earlier versions. This file is stored in Windows Installation drive C:\ntlar.

• boot.ini : Build the operating system selection menu in WindowsXP and earlier version. This file is stored in Windows installation drive c:\boot.ini.

System Reserved Partition

Windows 7 and 8 create a special System Reserved partition when installed on a clean disk. Windows does not assign a drive letters to this partitions. This partitions consumes 100 MB of space in Windows 7 and 350 MB on windows 8.

Advance Boot Options Menu

• Safe Mode : Starts a system with minimal set of files and drivers, including only the mouse, monitor, keyboard, mass storage, base video and default system services. No network support.

• Safe Mode with Networking : Adds network support to safe mode. usefull for debugging tools on a network drive.

• Safe Mode with Command Prompt : Loads safe mode but starts windows in a command prompt instead of GUI.

• Enable Boot Logging : Records boot drivers and objects during windows boot.

• Enable VGA mode : Starts Windows XP using the default VGA driver in 640X480 resolution with 256 colors.

• Last known goot configuration : Boots windows using the last successfull configuration (HKEY_LOCAL_MACHINE\System\Select\LastKnownGood).

• Starts Windows Normally : Performs a standard windows boot.

• Reboot : Restarts the system from scratch.

Bootloader Modification tools

• EasyBCD 2.2 : A tool for modyfying the bootloader in Windows Vista and Later Versions.

Accessing the EFI System Partition in Windows

Method 1: Using Disk Management

1. Press Win+R type diskmgmt.msc, and press Enter.

2. Locate the EFI System Partition (Usually labeled as EFI, System Reserved or a 100MB/200MB FAT32 partitions)

3. Right-Click the EFI partition and choose Change Drive Letter and Paths...

4. Click Add. select a drive letter(e.g. Z:) and click OK.

5. The EFI partition is now accessible via File-Explorer as Z:\.

Method 2: Using Command prompt

diskpart
list disk
select disk  X        # Replace X with the disk containing the EFI partition.
list partition
select partition Y    # Replace Y with EFI partition (usually a small FAT32 partition)
assign letter=Z       # Assign a drive letter
exit

Now, access the EFI partition via Z:\.

Method 3: Using Poweshell

mountvol Z: /s

this mounts the EFI partition as Z:\

Method 4: Accessing EFI Files via Command Line

Once the partition is mounted (Z:\), navigate using.

cd /d Z:\EFI
dir

you should see folders like;

• Boot

• Microsoft

• Ubuntu (if dual-booting with Linux)

• OEM (depending on the manufacturer)

To unmount the EFI partition, remove the assigned letter using diskpart :

diskpart
select volume Z
remove letter=Z
exit

Or Use:

mountvol Z: /D

Useful Commands for Boot Management

Windows Commands

bcdedit /enum                               #   view Current Boot Configuration
bcdedit /set {Current} safeboot minimal     #   Enable Safe Mode
bcdedit /set {Current} safeboot network     #   Enable Safe Mode with Networking
bcdedit /delete {ID}                        #   Delete a Boot entry
bootrec /fixmbr                             #   Repair Master Boot Record (MBR)
bootrec /fixboot                            #   Fix the Boot sector
bootrec /scanos                             #   Scan for installed operating systems
bootrec /rebuildbcd                         #   Rebuilds the boot configuration data

Linux Commands (GRUB Bootloader)

sudo update-grub                #   Update GRUB boot configuration
sudo grub-install /dev/sda      #   install GRUB to primary disk
cat /boot/grub/grub.cfg         #   View GRUB configuration

This Guide provides an overview of bootloaders, boot options and key commands for Windows and Linux Systems.