On Fri, May 10, 2019 at 06:27:17PM +0200, Thomas Schmitt wrote: > Hi, > > Florian Pelz wrote: > > This is not an install ISO but a USB install medium. The USB drive > > was written by the Windows Media Creation Tool. Copying instead a > > Windows ISO created by the Windows Media Creation Tool to a USB drive > > does *not* yield a bootable USB drive; it does not even boot on other > > computers. > > This would bring the MS-World back in sync with my understanding of UEFI > specs and other info sources. > > But there are substantial rumors that the ISO boots from USB stick. > Microsoft is said to advertise it for DVD+R DL and USB stick. > (I could not get my hands on ISO or advertising yet ...) > >
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 will continue testing the Windows 10 USB install medium: On Fri, May 10, 2019 at 03:46:56PM +0200, Thomas Schmitt wrote: > Hi, > > Florian Pelz wrote: > > I would like to test but on this bootable German Windows 10 > > 32-bit+64-bit USB install medium, the content is different. How would > > I find the offset in the USB image (you call it offset 454) which I > > should zero out to break Windows? > > That would be offset 454 in the EFI boot image: Start LBA field of MBR > partition 1. > > You may learn the block address of the image from xorriso: > > xorriso -indev "$ISO" -report_el_torito plain 2>/dev/null \ > | grep 'El Torito boot img : .* UEFI' > > should say something like > > El Torito boot img : 2 UEFI y none 0x0000 0x00 1 515 > > The last number 515 is the 2048-byte block address of the EFI image. > (That's from the japanese ISO mentioned at debian-user.) > > If you write four zero bytes at byte 515 * 2048 + 454 = 1055174, then > there is start LBA 0 in the slot of partition 1. This should trigger > the stalled boot process of the Macbook. > florian@florianmacbook ~$ sudo fdisk -l /dev/sdb Disk /dev/sdb: 7.5 GiB, 8053063680 bytes, 15728640 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: dos Disk identifier: 0x3093e6cb Device Boot Start End Sectors Size Id Type /dev/sdb1 * 2048 15728639 15726592 7.5G c W95 FAT32 (LBA) florian@florianmacbook ~$ sudo dd if=/dev/sdb of=windoof Password: 15728640+0 records in 15728640+0 records out 8053063680 bytes (8.1 GB, 7.5 GiB) copied, 324.929 s, 24.8 MB/s So I calculate 512*2048+454=1049030. I do: florian@florianmacbook ~$ sudo dd if=/dev/zero bs=1 count=16 seek=1049030 of=/dev/sdb It still boots. I believe what I calculated was wrong. I do not continue. > But maybe the other bytes from 446 to 461 hamper recognition as partition > table entry. So more similar to the mformat image would be to zeroize > bytes 446 to 509 to clear the partition table, and then to write to bytes > 446 to 461 what we see as partition slot 1 in the grub-mkrescue EFI > partition: > > 80 00 01 00 01 01 12 4f 00 00 00 00 40 0b 00 00 > Regards, Florian _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
