[syslinux] "isolinux.bin missing or corrupt" when booting USB flash drive in old PC

[Martin Str|mberg]

Thomas Schmitt wrote:
> David Christensen wrote:
> > # fdisk -l /dev/sdc
> > WARNING: GPT (GUID Partition Table) detected on '/dev/sdc'! The util
> > fdisk doesn't support GPT.
> 
> That's actually a bug in fdisk. The GPT is invalid because it is not
> announced by a "Protective MBR".
> 
> >    Device Boot      Start         End      Blocks   Id  System
> > /dev/sdc1   *           0     1325055      662528    0  Empty
> 
> "Empty" is not a realistic statement but just a human readable representation
> of partition tye 0x0. It is unusual but needed to avoid that UEFI sees
> partition 2 as nested partition inside partition 1.
> 
> > # parted /dev/sdc u s p
> > Warning: /dev/sdc contains GPT signatures, indicating that it has a GPT
> > table.  However, it does not have a valid fake msdos partition table, as
> > it should.
> 
> Smarter than fdisk.
> 
> > Is this a GPT partition table?
> > Yes/No? yes
> > Error: Both the primary and backup GPT tables are corrupt.
> 
> That's because of the nested GPT partitions, i assume.

Well, I consider warning and giving output of the existing MBR that it
does understands better than just bailing out like parted does.

I have been having successful outputs from gdisk in cases like
this, IIRC. Try that.

> > I need a debugging version of whatever program is generating the error
> > message "isolinux.bin missing or corrupt".
> 
> That would be the MBR code at bytes 0 to 432 of the ISO.
> Source code (assembler) is at
>   http://git.zytor.com/syslinux/syslinux.git/tree/mbr/isohdpfx.S
> 
> It's a very narrow piece of space for a program. One may re-use the
> "nop" bytes at label "_start:". They serve as fake Apple Partition Map
> header block.
> If the first ".byte 0x33, 0xed" before the "nop"s gets removed then the
> second one after the "nop"s needs to be removed, too.

Why? There's no reason from coding perpesctive. That's an xor bp, bp.


-- 
MartinS