[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: grub-mkrescue: Problem with MBR partition table at start of EFI part
From: |
Thomas Schmitt |
Subject: |
Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition |
Date: |
Sat, 11 May 2019 14:05:25 +0200 |
Hi,
> The Windows 8.1 ISO image that I downloaded from Microsoft yesterday
> also cannot be booted from a USB drive on neither this Macbook or
> another computer.
I wonder how other people can get to the impression that their attempts
succeeded. (Will have to wait for somebody who is willing to go on with
experiments after perceived success.)
> I will continue testing the Windows 10 USB install medium:
> /dev/sdb1 * 2048 15728639 15726592 7.5G c W95 FAT32 (LBA)
That's not an EFI System Partition.
So i assume the USB stick boots by BIOS and x86 machine code in the MBR.
Unless we believe in EFI firmware that hops on arbitrary partitions ...
> So I calculate 512*2048+454=1049030.
> address@hidden ~$ sudo dd if=/dev/zero bs=1 count=16 seek=1049030
> of=/dev/sdb
> It still boots. I believe what I calculated was wrong.
You zeroized the LBA field but also the block count field.
It should have been count=4 for the most minimal surgery (LBA=0x00000000).
With count=16 you would have to seek to 512*2048+446 and afterwards would
have to write a new partition table entry with LBA=0, non-zero block count,
and probably a non-zero partition type.
> I do not continue.
Then let's disinfect our brains and go on with some useful work. :))
Have a nice day :)
Thomas
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/01
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Chris Murphy, 2019/05/09
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/09
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/10
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition,
Thomas Schmitt <=
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/13
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/14
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/15
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/15
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/16
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/16