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From: Warren Block on 13 Dec 2009 18:50
Justin <justin(a)nobecauseihatespam.com> wrote:
> On 12/13/09 4:06 PM, Warren Block wrote:

>>> It worked! Thanks Warren.
>>> justin$ dd if=/dev/disk2 bs=2k | head -c 769736704 | openssl md5
>>> 6b8df7fb34d5960ecf91a291926a1e6f
>>> Justins-MacBook-Pro:~ justin$ openssl md5 8.0-RELEASE-ia64-dvd1.iso
>>> MD5(8.0-RELEASE-ia64-dvd1.iso)= 6b8df7fb34d5960ecf91a291926a1e6f
>>
>> The head -c command should be unnecessary and might cause that line to
>> lie to you. If the data read from disk doesn't match the ISO file,
>> there's an error. Does dd if=/dev/disk2 bs=2k | md5 give a different
>> result?
>
> Yes, because it is running the hash on the entire disk - including the
> random junk outside the bounds of what I burned.

Maybe something to do with OSX. On FreeBSD, you don't get anything back
from a dd of a CD/DVD that wasn't put there, presumably because it hits
EOF and exits. In fact, 'dd if=/dev/acd0 of=file.iso bs=2k' is how you
make a file copy of a CD or DVD.

> however I ran into something else
>
> justin$ dd if=/dev/disk2 bs=2k | head -c 7771521024 | md5 -r
> head: *illegal byte count* -- 7771521024
> d41d8cd98f00b204e9800998ecf8427e

Seems reasonable for head to return an error when the count is larger
than the input file.

--
Warren Block * Rapid City, South Dakota * USA
From: Justin on 13 Dec 2009 23:06
On 12/13/09 6:50 PM, Warren Block wrote:
> Justin<justin(a)nobecauseihatespam.com> wrote:
>> On 12/13/09 4:06 PM, Warren Block wrote:
>
>>>> It worked! Thanks Warren.
>>>> justin$ dd if=/dev/disk2 bs=2k | head -c 769736704 | openssl md5
>>>> 6b8df7fb34d5960ecf91a291926a1e6f
>>>> Justins-MacBook-Pro:~ justin$ openssl md5 8.0-RELEASE-ia64-dvd1.iso
>>>> MD5(8.0-RELEASE-ia64-dvd1.iso)= 6b8df7fb34d5960ecf91a291926a1e6f
>>>
>>> The head -c command should be unnecessary and might cause that line to
>>> lie to you. If the data read from disk doesn't match the ISO file,
>>> there's an error. Does dd if=/dev/disk2 bs=2k | md5 give a different
>>> result?
>>
>> Yes, because it is running the hash on the entire disk - including the
>> random junk outside the bounds of what I burned.
>
> Maybe something to do with OSX. On FreeBSD, you don't get anything back
> from a dd of a CD/DVD that wasn't put there, presumably because it hits
> EOF and exits. In fact, 'dd if=/dev/acd0 of=file.iso bs=2k' is how you
> make a file copy of a CD or DVD.
>
>> however I ran into something else
>>
>> justin$ dd if=/dev/disk2 bs=2k | head -c 7771521024 | md5 -r
>> head: *illegal byte count* -- 7771521024
>> d41d8cd98f00b204e9800998ecf8427e
>
> Seems reasonable for head to return an error when the count is larger
> than the input file.
>

Yes, I realized I C&Ped the wrong value from a different dvd I am trying
to verify and make sure I have this method down.

Now what am I doing wrong here?

Running it on the original pressed dvd.

justin$ dd if=/dev/disk2 | md5 -r
15178752+0 records in
15178752+0 records out
7771521024 bytes transferred in 2836.421946 secs (2739903 bytes/sec)
9c74731407152250dec71f7d996d96b8

Making the iso file.

justin$ dd if=/dev/disk2 of=~/biggerdvd.iso
15178752+0 records in
15178752+0 records out
7771521024 bytes transferred in 2780.214384 secs (2795296 bytes/sec)

justin$ dd if=biggerdvd.iso bs=2k | md5 -r
3794688+0 records in
3794688+0 records out
7771521024 bytes transferred in 160.517571 secs (48415391 bytes/sec)
e26826cc68281aa581cc181483bd232d
From: Warren Block on 13 Dec 2009 23:27
Justin <justin(a)nobecauseihatespam.com> wrote:
> Now what am I doing wrong here?
>
> Running it on the original pressed dvd.
>
> justin$ dd if=/dev/disk2 | md5 -r
> 15178752+0 records in
> 15178752+0 records out
> 7771521024 bytes transferred in 2836.421946 secs (2739903 bytes/sec)
> 9c74731407152250dec71f7d996d96b8

Needs bs=2k on the dd command. Without that, dd is reading 512-byte
blocks, which gives 15178752*512 = 7771521024. Every time you're
reading from an actual data CD or DVD, it needs that.

> Making the iso file.
>
> justin$ dd if=/dev/disk2 of=~/biggerdvd.iso
> 15178752+0 records in
> 15178752+0 records out
> 7771521024 bytes transferred in 2780.214384 secs (2795296 bytes/sec)

Also needs bs=2k.

> justin$ dd if=biggerdvd.iso bs=2k | md5 -r
> 3794688+0 records in
> 3794688+0 records out
> 7771521024 bytes transferred in 160.517571 secs (48415391 bytes/sec)
> e26826cc68281aa581cc181483bd232d

A plain file is not a block device, so here's the spot you *don't* need
the bs=2k setting.

--
Warren Block * Rapid City, South Dakota * USA
From: Justin on 14 Dec 2009 13:14
On 12/13/09 11:27 PM, Warren Block wrote:
> Justin<justin(a)nobecauseihatespam.com> wrote:
>> Now what am I doing wrong here?
>>
>> Running it on the original pressed dvd.
>>
>> justin$ dd if=/dev/disk2 | md5 -r
>> 15178752+0 records in
>> 15178752+0 records out
>> 7771521024 bytes transferred in 2836.421946 secs (2739903 bytes/sec)
>> 9c74731407152250dec71f7d996d96b8
>
> Needs bs=2k on the dd command. Without that, dd is reading 512-byte
> blocks, which gives 15178752*512 = 7771521024. Every time you're
> reading from an actual data CD or DVD, it needs that.
>
>> Making the iso file.
>>
>> justin$ dd if=/dev/disk2 of=~/biggerdvd.iso
>> 15178752+0 records in
>> 15178752+0 records out
>> 7771521024 bytes transferred in 2780.214384 secs (2795296 bytes/sec)
>
> Also needs bs=2k.
>
>> justin$ dd if=biggerdvd.iso bs=2k | md5 -r
>> 3794688+0 records in
>> 3794688+0 records out
>> 7771521024 bytes transferred in 160.517571 secs (48415391 bytes/sec)
>> e26826cc68281aa581cc181483bd232d
>
> A plain file is not a block device, so here's the spot you *don't* need
> the bs=2k setting.
>

It works! w00t!

justin$ dd if=/dev/disk2 bs=2k | md5 -r
3794688+0 records in
3794688+0 records out
7771521024 bytes transferred in 2593.040306 secs (2997069 bytes/sec)
e26826cc68281aa581cc181483bd232d

justin$ dd if=/dev/disk2 of=biggerdvd.iso bs=2k
3794688+0 records in
3794688+0 records out
7771521024 bytes transferred in 2765.505716 secs (2810163 bytes/sec)

justin$ md5 -r biggerdvd.iso
e26826cc68281aa581cc181483bd232d biggerdvd.iso
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