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From: David Empson on 11 Dec 2009 20:32
Justin <justin(a)nobecauseihatespam.com> wrote:

> On 12/11/09 4:14 AM, David Empson wrote:
> > Justin<justin(a)nobecauseihatespam.com> wrote:
> >
> >> How can I run the md5 command on a DVD?
> >> I tried $ md5 if=/dev/disk2
> >> md5: if=/dev/disk2: No such file or directory
> >
> > You seem to be mixing up the syntax of two commands. "if=" is one of the
> > options for the 'dd' tool.
> >
> >> Basically I downloaded the FreeBSD ISOs and I must now verify the DVDs
> >> I burned are error free.
> >>
> >> I can run it on the iso file no problem.
> >> the -r flag produces standard md5 output.
> >> Justin$ md5 -r blahblah.iso
> >> 9bd9bb86fbaacda6862a89f24be80d85 blahblah.iso
> >>
> >> as opposed to
> >>
> >> Justin$ md5 blahblah.iso
> >> MD5 (blahblah.iso) = 9bd9bb86fbaacda6862a89f24be80d85
> >>
> >> So yeah, how can I get an md5 value from an actual DVD?
> >
> > You should be able to get an md5 as follows:
> >
> > md5 -r /dev/disk2
> >
> > but you might need to specify a particular session/partition on the DVD,
> > such as
> >
> > md5 -r /dev/disk2s1
> >
> > and you might need to unmount it first (without ejecting) to avoid
> > conflicts with the system.
> >
>
> I'm not sure what its running the md5 on but this is what I get.
>
> Justin$ dd if=/dev/disk2 of=test.iso
> 1380720+1 records in
> 1380720+1 records out
> 706928880 bytes transferred in 468.416814 secs (1509188 bytes/sec)
>
>
> Justin$ md5 -r test.iso
> 82487f9cea928fa339bd7c3f6e492981 test.iso
> Justins-Macbook-Pro:~ Justin$ md5 -r /dev/disk2
> d41d8cd98f00b204e9800998ecf8427e /dev/disk2

I'm also not sure what is going on there.

dd will be copying with its default block size of 512 bytes. For some
reason the number of bytes copied is not an exact multiple of 512, which
is odd for a DVD (I don't know offhand what sector size they use).

You didn't specify any sync options for dd, so it wouldn't have forced
512 byte padding on either the input or output side.

I would have expected that to produce the same checksum, but there could
be something else going on.

--
David Empson
dempson(a)actrix.gen.nz
From: Justin on 12 Dec 2009 14:07
On 12/11/09 8:32 PM, David Empson wrote:
> Justin<justin(a)nobecauseihatespam.com> wrote:
>
>> On 12/11/09 4:14 AM, David Empson wrote:
>>> Justin<justin(a)nobecauseihatespam.com> wrote:
>>>
>>>> How can I run the md5 command on a DVD?
>>>> I tried $ md5 if=/dev/disk2
>>>> md5: if=/dev/disk2: No such file or directory
>>>
>>> You seem to be mixing up the syntax of two commands. "if=" is one of the
>>> options for the 'dd' tool.
>>>
>>>> Basically I downloaded the FreeBSD ISOs and I must now verify the DVDs
>>>> I burned are error free.
>>>>
>>>> I can run it on the iso file no problem.
>>>> the -r flag produces standard md5 output.
>>>> Justin$ md5 -r blahblah.iso
>>>> 9bd9bb86fbaacda6862a89f24be80d85 blahblah.iso
>>>>
>>>> as opposed to
>>>>
>>>> Justin$ md5 blahblah.iso
>>>> MD5 (blahblah.iso) = 9bd9bb86fbaacda6862a89f24be80d85
>>>>
>>>> So yeah, how can I get an md5 value from an actual DVD?
>>>
>>> You should be able to get an md5 as follows:
>>>
>>> md5 -r /dev/disk2
>>>
>>> but you might need to specify a particular session/partition on the DVD,
>>> such as
>>>
>>> md5 -r /dev/disk2s1
>>>
>>> and you might need to unmount it first (without ejecting) to avoid
>>> conflicts with the system.
>>>
>>
>> what if the dvd has two sessions?
>
> DVDs generally don't support sessions, but if you use 'diskutil list'
> you can see all the mounted volumes. It numbers the partitions or
> sessions. Number 0 is the base device (such as 'disk2') or possibly the
> partition table on a hard drive. Numbers 1 and higher use 's' followed
> by the number appended to the disk name, e.g.

Are you sure? The Snnow Leopard DVD I just bought has a Windows session
on it.
From: Geoffrey S. Mendelson on 12 Dec 2009 15:34
Justin wrote:
> Are you sure? The Snnow Leopard DVD I just bought has a Windows session
> on it.

The Snow Leopard disks from Apple did in fact have two sessions on them,
one was Snow Leopard install and the other was BootCamp. There also was
a partition table, etc on it.

The bootleg versions on the Internet were either. Most were just the Snow
Leopard session (and therefore not bootable), others were the complete
disk image.

If someone gives you a copied disk that has just the Snow Leopard install,
either they copied it incorrectly, or downloaded it from the Internet.
Caveat Emptor.

BTW, if you have MacPorts installed, you can just install md5sum, and have
one that is compatible with everything else.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm(a)mendelson.com N3OWJ/4X1GM
From: Justin on 12 Dec 2009 16:41
On 12/11/09 8:32 PM, David Empson wrote:
> Justin<justin(a)nobecauseihatespam.com> wrote:
>
>> On 12/11/09 4:14 AM, David Empson wrote:
>>> Justin<justin(a)nobecauseihatespam.com> wrote:
>>>
>>>> How can I run the md5 command on a DVD?
>>>> I tried $ md5 if=/dev/disk2
>>>> md5: if=/dev/disk2: No such file or directory
>>>
>>> You seem to be mixing up the syntax of two commands. "if=" is one of the
>>> options for the 'dd' tool.
>>>
>>>> Basically I downloaded the FreeBSD ISOs and I must now verify the DVDs
>>>> I burned are error free.
>>>>
>>>> I can run it on the iso file no problem.
>>>> the -r flag produces standard md5 output.
>>>> Justin$ md5 -r blahblah.iso
>>>> 9bd9bb86fbaacda6862a89f24be80d85 blahblah.iso
>>>>
>>>> as opposed to
>>>>
>>>> Justin$ md5 blahblah.iso
>>>> MD5 (blahblah.iso) = 9bd9bb86fbaacda6862a89f24be80d85
>>>>
>>>> So yeah, how can I get an md5 value from an actual DVD?
>>>
>>> You should be able to get an md5 as follows:
>>>
>>> md5 -r /dev/disk2
>>>
>>> but you might need to specify a particular session/partition on the DVD,
>>> such as
>>>
>>> md5 -r /dev/disk2s1
>>>
>>> and you might need to unmount it first (without ejecting) to avoid
>>> conflicts with the system.
>>>
>>
>> I'm not sure what its running the md5 on but this is what I get.
>>
>> Justin$ dd if=/dev/disk2 of=test.iso
>> 1380720+1 records in
>> 1380720+1 records out
>> 706928880 bytes transferred in 468.416814 secs (1509188 bytes/sec)
>>
>>
>> Justin$ md5 -r test.iso
>> 82487f9cea928fa339bd7c3f6e492981 test.iso
>> Justins-Macbook-Pro:~ Justin$ md5 -r /dev/disk2
>> d41d8cd98f00b204e9800998ecf8427e /dev/disk2
>
> I'm also not sure what is going on there.
>
> dd will be copying with its default block size of 512 bytes. For some
> reason the number of bytes copied is not an exact multiple of 512, which
> is odd for a DVD (I don't know offhand what sector size they use).
>
> You didn't specify any sync options for dd, so it wouldn't have forced
> 512 byte padding on either the input or output side.
>
> I would have expected that to produce the same checksum, but there could
> be something else going on.
>

When I ran the md5 command on dev/disk2 the drive does not activate - it
is instant. So its not running an md5 on the disk.
God knows what its running the md5 hash on.
From: Justin on 12 Dec 2009 16:51
On 12/12/09 3:34 PM, Geoffrey S. Mendelson wrote:
> Justin wrote:
>> Are you sure? The Snnow Leopard DVD I just bought has a Windows session
>> on it.
>
> The Snow Leopard disks from Apple did in fact have two sessions on them,
> one was Snow Leopard install and the other was BootCamp. There also was
> a partition table, etc on it.
>
> The bootleg versions on the Internet were either. Most were just the Snow
> Leopard session (and therefore not bootable), others were the complete
> disk image.
>
> If someone gives you a copied disk that has just the Snow Leopard install,
> either they copied it incorrectly, or downloaded it from the Internet.
> Caveat Emptor.
>
> BTW, if you have MacPorts installed, you can just install md5sum, and have
> one that is compatible with everything else.
>
> Geoff.
>

I actually have a real version of the DVD - I paid $30 for it because I
don't trust OS installs from the internets.
Now my problem is I downloaded the FreeBSD isos and need to verify them
for integrity.
There should be a way to run an md5 on the entire device.
As for macports and m5dsum
justin$ sudo port install md5sum
Password:
Error: Port md5sum not found
and
justin$ sudo port install md5
Error: Port md5 not found

Snow Leopard already has md5 installed and the -r flag produces the
standard output most scripts expect.
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