Re: Partial success and strange partial failure -was [Re: Physically have install DVD set. Want ISO's from which they came.]

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

Hi,

> On Sb, 01 mar 14, 14:38:14, Richard Owlett wrote:
> > root@minimal-squeeze:/home/richard# dd if=/dev/cdrom bs=2048
> > count=1939608 of=/home/richard/myiso1.iso conv=notrunc
> > [...]
> > root@minimal-squeeze:/home/richard# dd if=/home/richard/myiso1.iso
> > bs=2048 count=1939608 of=/dev/sdb conv=notrunc

Andrei POPESCU wrote:

> Not sure if this makes a differences, but why the count= and conv= ?
> To keep things simple, could you please retry with
>    cp /home/richard/myiso1.iso /dev/sdb

Both copy gestures for /dev/sdb are equivalent and should be ok.

The conv=1939608 in the first dd command is necessary, if the MD5
of the resulting .iso file shall match the published MD5 of the
Debian .iso. Most DVD types would return more bytes after the end
of the ISO filesystem.

The second count=1939608 is advisable, because the first dd command
used conv=notrunc. Just in case that /home/richard/myiso1.iso existed
before, and was larger than 1939608 * 2048 bytes.

One could simplify the copy procedure by skipping the intermediate .iso
file:

  dd if=/dev/cdrom bs=2048 count=1939608 of=/dev/sdb

Whatever method was used, the MD5 sum of the resulting copy can be
determined by:

  dd if=/dev/sdb bs=2048 count=1939608 | md5sum -

and should match the published MD5 of the Debian ISO image.


Have a nice day :)

Thomas