Re: sha512sum-error at debian-live-11.5.0-amd64-gnome.iso

Hi,

Gerd Mühlenbruch wrote:
> So, it seems to be a problem of nautilus on my computer.

wget -c still has a share in this.
But currently i have no ideas how to find out what makes an incomplete
nautilus download so confusing for wget.


> dd if=debian-11.5.0-amd64-netinst.iso bs=1 skip=400556032 | od -c | less
> >Ausgabe.txt

(My proposal to pipe into the pager "less" was meant to avoid the need
for redirection.)


> 1177740  \0  \0  \0   E   F   I       P   A   R   T  \0  \0 001  \0   \
> 1177760  \0  \0  \0 302 354 241 223  \0  \0  \0  \0 377 357  \v  \0  \0
> 1200000  \0  \0  \0 001  \0  \0  \0  \0  \0  \0  \0   @  \0  \0  \0  \0

This is a GPT header block signature, but not aligned to a full block
of 512 bytes, as GPT prescribes.
The "E" of "E   F   I" is supposed to be at the start of the block.
24 bytes from there on we have a little-endian 8-byte number which tells
the intended block address:

  (gdb) p 0377 + 0357 * 256 + '\v' * 256 * 256
  782335

This is the address of the last 512-block of the original ISO:

 782335 = 400556032 / 512 - 1

So we have a displaced copy of a GPT backup header with the proper
block address which it would have in the netinst ISO.
Checking this theory:

  dd if=debian-11.5.0-amd64-netinst.iso bs=512 skip=782335 | od -c

yields

  0000000   E   F   I       P   A   R   T  \0  \0 001  \0   \  \0  \0  \0
  0000020 302 354 241 223  \0  \0  \0  \0 377 357  \v  \0  \0  \0  \0  \0
  0000040 001  \0  \0  \0  \0  \0  \0  \0   @  \0  \0  \0  \0  \0  \0  \0
  0000060 312 357  \v  \0  \0  \0  \0  \0   f 027 253   N 247   r   5   B
  0000100 215 256   z   9 353       M 314 313 357  \v  \0  \0  \0  \0  \0
  0000120 320  \0  \0  \0 200  \0  \0  \0   1 231   o 227  \0  \0  \0  \0
  0000140  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0  \0
  *
  0001000

Both, the existence of the copy 327648 after the original end of the ISO
and its non-alignment by -29 (or 483) bytes are hard to explain.


Have a nice day :)

Thomas