egormkn / mbr-boot-manager

💾 Master Boot Record with a boot menu written in Assembly

MBR Boot Manager

Simple yet powerful Master Boot Record Boot manager that allows to select one of four primary partitions during the boot. Got tired with reinstalling Grub or other boot manager, that was overwritten by Windows? Now you can choose one of four primary partitions to boot with this tiny (512 bytes only) custom MBR.

Features

• Windows, Linux, FreeDOS and any other bootable partitions are supported
• Speeds up the boot process for your main OS
• Supports multiple active partitions
• Boot first active partition by default
• If Shift is pressed during boot, a boot menu will appear
  • Use UP and DOWN arrows to choose partition in boot menu
  • Use Enter to select the partition you want to boot from
  • Use Esc to reboot your computer
• Easy to install
• Uses only the first sector of disk (512 bytes)
• Absolutely free and open-source
• Well-documented and optimised code
• DIY: compile your own version with NASM

Installation

Windows

Download BootIce and run as Administrator. Select the disk, then Process MBR -> Restore MBR. Choose mbr.bin as restore file, make sure that "Keep signature and partition table untouched" is selected and choose "Restore".

Linux/Unix

Create a backup of your current MBR with dd if=/dev/sdX of=mbr_backup.bin bs=512 count=1.
Then run dd if=mbr.bin of=/dev/sdX bs=446 count=1 where X is a letter of the disk

Credits

• Egor Makarenko
• Andrew Plotnikov
• Vladislav Zemtsov

License

This is free and unencumbered software released into the public domain. See our LICENSE file for more information.

mbr-boot-manager's Issues

Reorganize repo

Strange files in root directory (buildboot, runboot, bochs-config) - remove from there

Does not work with any other bootable partitions ?

Hi,
I'm coding my own toy OS and I'm using your MBR Boot Manager. I made a simple kernel that prints "Hello" and put it in a FAT32 partition. For the FAT32 partition boot sector, I used a modified version of boot.asm from https://github.com/ishanthilina/USB-FAT32-Bootloader . I modified it to match my partition like so :

[BITS 16]
[ORG 0x0000]
jmp short START
nop

OEM_ID                db 		"MSWIN4.1"
BytesPerSector        dw 		512
SectorsPerCluster     db 		64
ReservedSectors       dw 		32
TotalFATs             db 		2
MaxRootEntries        dw 		0x0000
NumberOfSectors       dw 		0x0000
MediaDescriptor       db 		0xF0 ;F0 because I'm using Flash memory
SectorsPerFAT         dw 		0x0000
SectorsPerTrack       dw 		63
SectorsPerHead        dw 		255
HiddenSectors         dd 		0x00000800
TotalSectors          dd 		501251072
BigSectorsPerFAT      dd 		61181
Flags                 dw 		0x0000
FSVersion             dw 		0x0000
RootDirectoryStart    dd 		0x00000002
FSInfoSector          dw 		0x0001
BackupBootSector      dw 		0x0006

TIMES 12 DB 0 ;jumping to next offset

DriveNumber           db 		128
ReservedByte          db   		0
Signature             db 		0x29
VolumeID              dd 		0x0931FBD0
VolumeLabel           db 		"NO NAME    "
SystemID              db 		"FAT32   "

When I boot the computer, I can see the 4 partitions (I actually have only one partition but I understand why four partitions appears) on the flash drive. When I select the first and only (active) partition, the message "Boot sector error" and then reboot.

I tried debugging the MBR and from what I've seen, the code/condition that triggers the error message is the following :

CHECK_OS:
CMP WORD [0x7DFE], 0xAA55
JNZ PRINT_ERROR             ; Missing bootable mark <-- this part here

Clearly this shouldn't be happening because my FAT32 boot sector has the signature 0xAA55 (I can show the full FAT32.asm boot sector code if needed, it's just the same as https://github.com/ishanthilina/USB-FAT32-Bootloader expect for the aformentioned changes I made).

EDIT : The FAT32 Partition starts at sector 2048