Re: iso hacked suspicious: answers

["Thomas Schmitt" <scdbackup@gmx.net>]

Hi,

Andrew F Comly wrote:
> E) Burn iso to media
> dd if=/dev/zero of=/dev/sdb1 bs=1M;
> wait;

Why this overwriting of partition 1 by zeros ?
The partition table will be overwritten by the ISO anyways.

(And on what asynchronous processes are you waiting to end ?)


> ddif=/media/LG/AC/bckup/Install/2_Bootable-OS/Debian/i386/debian-8.5.0-i386-l
xde-CD-1.iso of=/dev/sdb

Blanks matter. :))

Assumed that you did put a blank between "dd" and "/media", the command
would be ok for copying the ISO onto a USB stick at /dev/sdb.
(For me it runs substantially faster if i add option bs=1M.)

Did the command last long enough to be credible ?
Did it report
  1255424+0 records in
  1255424+0 records out
?


>             sudo sha256sum /dev/sdb

As we learn from the copy-to-stick command, we need to curb to 1255424
blocks of dd's default size (512 bytes per block). My USB stick is at
/dev/sdc:

  $ dd if=/dev/sdc count=1255424 | sha256sum
  ...
  fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886  -

  $ fgrep fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886 SHA256SUMS
  fd7729e3bdfcb2b1b8793f5a19096fb2eee3cf709c39112ed2da7e7a2d7f6886  debian-8.5.0-i386-lxde-CD-1.iso


Testing with ./check_debian_iso (which counts blocks of 2048 bytes each):

  $ ./check_debian_iso SHA512SUMS debian-8.5.0-i386-lxde-CD-1.iso /dev/sdc
  Piping 313856 blocks of '/dev/sdc' through 'sha256sum'
  to verify checksum list item 'debian-8.5.0-i386-lxde-CD-1.iso'.
  313856+0 records in
  313856+0 records out
  642777088 bytes (643 MB) copied, 31.7854 s, 20.2 MB/s
  Ok: '/dev/sdc' matches 'debian-8.5.0-i386-lxde-CD-1.iso' in 'SHA256SUMS'


Have a nice day :)

Thomas