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Re: Trouble making bootable USB from ISO image


Mark Fletcher wrote:
> root@kazuki:/home/mark# xorriso -indev
> ~mark/Downloads/Win10_1809Oct_v2_Japanese_x64.iso -report_system_area plain
> -report_el_torito plain
> ...
> Media summary: 1 session, 2591375 data blocks, 5061m data,  631g free
> Volume id    : 'CCCOMA_X64FRE_JA-JP_DV9'
> xorriso : NOTE : No System Area was loaded
> El Torito catalog  : 22  1
> El Torito images   :   N  Pltf  B   Emul  Ld_seg  Hdpt  Ldsiz         LBA
> El Torito boot img :   1  BIOS  y   none  0x0000  0x00      8         513
> El Torito boot img :   2  UEFI  y   none  0x0000  0x00      1         515
> El Torito img blks :   1  2
> El Torito img blks :   2  2590860

There is indeed no partition table to see in the ISO.
So at least EFI won't recognize it as bootable from USB stick.

It has El Torito boot equipment for DVD. Usable with legacy BIOS and
with EFI.

Whether it has usable MBR boot code for old BIOS would have to
be checked by e.g. cprogram "file".
This is how it would lool like if there was a MBR signature:

  $ file debian-9.3.0-amd64-netinst.iso
  debian-9.3.0-amd64-netinst.iso: DOS/MBR boot sector ...

(This would not necessarily mean that it contains x86 boot code.
 But at least it could. Then you could try CSM Legacy mode with your
 EFI firmware.)

> The only thing there that catches my untutored eye is the thing about
> the El Torito boot information being currently set to be discarded --
> doesn't sound healthy.
> xorriso : NOTE : Detected El-Torito boot information which currently is set
> to be discarded

It is only an announcement of xorriso that an ISO-to-ISO copy will not
preserve bootability with the current settings about boot equipment.
(Severity "NOTE" is rather harmless. "WARNING" and "SORRY" indicate minor
flaws. "FAILURE" and "FATAL" mean your xorriso run failed substantially.)


If no boot equipment is present for hard-disk-like devices, then you
probably have a use case for something like Rufus

But you may first try a hack:

We now know that the EFI boot image begins at 2048-bytes block 515.
In principle it will work as EFI System Partition too. (Question is
whether the software in it can work with anything else but DVD.)

So you could use a partition editor to create an MBR partition of type
"EF" which begins at 512-block 515 * 4 = 2060 and has 2,590,860 * 4 =
10,363,440 blocks.
(The EFI image is probably smaller. But El Torito can mark only sizes
 up to 32 MiB or unlimited size. Microsoft decided for unlimited. So
 the only limit is the ISO's end.)

MBR partition is less tricky than GPT. If it must be GPT, then create a
partition of the proposed start and size and Type GUID
C12A7328-F81F-11D2-BA4B-00A0C93EC93B . (Do this only if the ISO is already
copied to USB stick. Putting GPT into the image file could overwrite its
last few blocks by GPT backup.)


In the end i wonder about the ISO's size of 5 GiB. Too much for a normal
single-layer DVD. One would have to use DVD+R DL or BD media.
Was this announced by the download site ?

(The "DV9" at the end of the Volume Id could be a hint for DVD+R DL.)

Have a nice day :)