[Debburn-devel] Write iso/isohybrid on pendrive:problem

[Thomas Schmitt]

Hi,

> [with] debian-7.2.0-i386-lxde-CD-1.iso > /dev/sdb
> [...] debian-live-7.2-i386-lxde-desktop+nonfree.iso
> I can re-format the free space present on usb

These two images have MBRs with partition 1 beginning at
block 64 (= 32 KB). See e.g. output of
  /sbin/fdisk -lu debian-7.2.0-i386-lxde-CD-1.iso
  
They have obviously been created with xorrisofs options
-isohybrid-mbr and -partition_offset 16.


> When change file in to: isohybrid debian-7.2.0-i386-lxde-CD-1.iso

ISOLINUX program isohybrid produces an MBR with partition 1
starting at block 0. This overwrites the MBR produced by
xorriso.

There is not much other difference to be expected between
the downloaded ISO and its state after the isohybrid run.
So i assume this must be the cause.

One may test this theory by setting byte 448 of the isohybrid
result to 1 and byte 454 to 0. The ISO is prepared to work with
that start address to. But program isohybrid did not know.


> cat debian-7.2.0-i386-lxde-CD-1.iso > /dev/sdb
> on pendrive, with filesystem ext2 or Fat32

After that cat command, the filesystems are overwritten or at
least unreachable.


Have a nice day :)

Thomas