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Old 11-02-2009, 11:02 PM
NoOp
 
Default Jaunty Jackalope (RESOLVED)

On 11/02/2009 03:51 PM, John Graddy wrote:
> Thanks to all who responded. I now have what I need. However, I do
> have a new question.
>
> I have downloaded a release to one computer. I did an MD5SUM and all is
> OK. However, if I copy the iso file to a usb flash drive and move it to
> a different computer, I get a totally different md5sum on the file after
> I put it on the hard disk.
>
> Is something getting changed in the transfer process that I'm using???

No. The md5sum will change when you transfer the iso.



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Old 11-03-2009, 01:42 AM
John Graddy
 
Default Jaunty Jackalope (RESOLVED)

On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
> On 11/02/2009 03:51 PM, John Graddy wrote:
> > Thanks to all who responded. I now have what I need. However, I do
> > have a new question.
> >
> > I have downloaded a release to one computer. I did an MD5SUM and all is
> > OK. However, if I copy the iso file to a usb flash drive and move it to
> > a different computer, I get a totally different md5sum on the file after
> > I put it on the hard disk.
> >
> > Is something getting changed in the transfer process that I'm using???
>
> No. The md5sum will change when you transfer the iso.
>
>
>
I'm continually impressed by the knowledge of folks on this list.

I didn't have a clue that the md5sum would change. How do you learn
about that kind of stuff??

Thanks,
John



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Old 11-03-2009, 01:50 AM
NoOp
 
Default Jaunty Jackalope (RESOLVED)

On 11/02/2009 06:42 PM, John Graddy wrote:
> On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
>> On 11/02/2009 03:51 PM, John Graddy wrote:
>> > Thanks to all who responded. I now have what I need. However, I do
>> > have a new question.
>> >
>> > I have downloaded a release to one computer. I did an MD5SUM and all is
>> > OK. However, if I copy the iso file to a usb flash drive and move it to
>> > a different computer, I get a totally different md5sum on the file after
>> > I put it on the hard disk.
>> >
>> > Is something getting changed in the transfer process that I'm using???
>>
>> No. The md5sum will change when you transfer the iso.
>>
>>
>>
> I'm continually impressed by the knowledge of folks on this list.
>
> I didn't have a clue that the md5sum would change. How do you learn
> about that kind of stuff??

From this list :-) There was quite a discussion about this very issue
some time ago. I'll see if I can dig out the thread tomorrow.




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Old 11-03-2009, 01:50 AM
Karl Auer
 
Default Jaunty Jackalope (RESOLVED)

On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
> > No. The md5sum will change when you transfer the iso.

Why? The .iso is just a file, shouldn't it always have the same md5sum?
In fact, if it doesn't, what is the point of the md5sum?

Not contradicting you, just surprised and curious.

Regards, K.

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http://www.biplane.com.au/~kauer/ +61-428-957160 (mob)

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Old 11-03-2009, 02:07 AM
NoOp
 
Default Jaunty Jackalope (RESOLVED)

On 11/02/2009 06:50 PM, Karl Auer wrote:
> On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
>> > No. The md5sum will change when you transfer the iso.
>
> Why? The .iso is just a file, shouldn't it always have the same md5sum?
> In fact, if it doesn't, what is the point of the md5sum?
>
> Not contradicting you, just surprised and curious.
>
> Regards, K.
>
>

Can't find the exact thread just now, but I do recall a thread where
this was discussed & made a point of it in this thread back in March:
https://lists.ubuntu.com/archives/ubuntu-users/2009-March/176290.html

I'll look further tomorrow.

Gary



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Old 11-03-2009, 02:24 AM
James Michael Fultz
 
Default Jaunty Jackalope (RESOLVED)

* NoOp <glgxg@sbcglobal.net> [2009-11-02 18:50 -0800]:
> On 11/02/2009 06:42 PM, John Graddy wrote:
> > On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
> >> No. The md5sum will change when you transfer the iso.
> >>
> > I'm continually impressed by the knowledge of folks on this list.
> >
> > I didn't have a clue that the md5sum would change. How do you learn
> > about that kind of stuff??
>
> From this list :-) There was quite a discussion about this very issue
> some time ago. I'll see if I can dig out the thread tomorrow.

Then someone was misinformed. The MD5 sum should match if a file copy
operation is error-free. Copying a file between storage devices is
equivalent to downloading it for as much as the MD5 sum should remain
consistent. Just today I copied an ISO between two disks and was able
to verify by MD5 sum.

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Old 11-03-2009, 02:32 AM
NoOp
 
Default Jaunty Jackalope (RESOLVED)

On 11/02/2009 07:07 PM, NoOp wrote:
> On 11/02/2009 06:50 PM, Karl Auer wrote:
>> On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
>>> > No. The md5sum will change when you transfer the iso.
>>
>> Why? The .iso is just a file, shouldn't it always have the same md5sum?
>> In fact, if it doesn't, what is the point of the md5sum?
>>
>> Not contradicting you, just surprised and curious.
>>
>> Regards, K.
>>
>>
>
> Can't find the exact thread just now, but I do recall a thread where
> this was discussed & made a point of it in this thread back in March:
> https://lists.ubuntu.com/archives/ubuntu-users/2009-March/176290.html

Here is a recent real life example. I downloaded the most recent karmic
liveCD so that I could test an inplace reinstall on karmic for Emil
Payne (see the "Dist Upgrade" thread. Note to Emil - works with Karmic
live CD BTW so there is hope).

I now check the md5sum of the iso:

$ md5sum ubuntu-9.10-desktop-i386.iso
8790491bfa9d00f283ed9dd2d77b3906 ubuntu-9.10-desktop-i386.iso

and see that it matches:
http://releases.ubuntu.com/karmic/MD5SUMS
8790491bfa9d00f283ed9dd2d77b3906 *ubuntu-9.10-desktop-i386.iso

Now I burn the iso to a cd & check the md5sum of that cd:
$ md5sum /dev/cdrom
8790491bfa9d00f283ed9dd2d77b3906 /dev/cdrom

And I've just now proven myself wrong :-( The md5sum of the CD matches
that of the iso. So apologies to the list, and to John Graddy. I'll
still see if I can find the thread tomorrow, but mea culpa & apologies
to all.





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Old 11-03-2009, 02:37 AM
Rashkae
 
Default Jaunty Jackalope (RESOLVED)

John Graddy wrote:

>>>
>>> Is something getting changed in the transfer process that I'm using???
>> No. The md5sum will change when you transfer the iso.
>>
>>
>>
> I'm continually impressed by the knowledge of folks on this list.
>
> I didn't have a clue that the md5sum would change. How do you learn
> about that kind of stuff??
>

Eh, I'm having trouble figuring out if that was sarcasm, or if you
really believed that trite.


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Old 11-03-2009, 02:49 AM
Rashkae
 
Default Jaunty Jackalope (RESOLVED)

NoOp wrote:
> On 11/02/2009 07:07 PM, NoOp wrote:
>> On 11/02/2009 06:50 PM, Karl Auer wrote:
>>> On Mon, 2009-11-02 at 16:02 -0800, NoOp wrote:
>>>>> No. The md5sum will change when you transfer the iso.
>>> Why? The .iso is just a file, shouldn't it always have the same md5sum?
>>> In fact, if it doesn't, what is the point of the md5sum?
>>>
>>> Not contradicting you, just surprised and curious.
>>>
>>> Regards, K.
>>>
>>>
>> Can't find the exact thread just now, but I do recall a thread where
>> this was discussed & made a point of it in this thread back in March:
>> https://lists.ubuntu.com/archives/ubuntu-users/2009-March/176290.html
>
> Here is a recent real life example. I downloaded the most recent karmic
> liveCD so that I could test an inplace reinstall on karmic for Emil
> Payne (see the "Dist Upgrade" thread. Note to Emil - works with Karmic
> live CD BTW so there is hope).
>
> I now check the md5sum of the iso:
>
> $ md5sum ubuntu-9.10-desktop-i386.iso
> 8790491bfa9d00f283ed9dd2d77b3906 ubuntu-9.10-desktop-i386.iso
>
> and see that it matches:
> http://releases.ubuntu.com/karmic/MD5SUMS
> 8790491bfa9d00f283ed9dd2d77b3906 *ubuntu-9.10-desktop-i386.iso
>
> Now I burn the iso to a cd & check the md5sum of that cd:
> $ md5sum /dev/cdrom
> 8790491bfa9d00f283ed9dd2d77b3906 /dev/cdrom
>
> And I've just now proven myself wrong :-( The md5sum of the CD matches
> that of the iso. So apologies to the list, and to John Graddy. I'll
> still see if I can find the thread tomorrow, but mea culpa & apologies
> to all.
>
>

You're comparing the md5sum from a file to that of a CD. They will
sometimes not match because the lead out from writing to a cd appends
some nulls. It seems to depend on type of drive and exact command used
to burn cd, but either way, you cannot reliably compare md5sum of an iso
with the cdrom dev device. Rather, use isoinfo command to get the
exactly number of bytes, and use dd to pipe that from the cd to md5sum

Example: isodinfo -d -i /dev/cdrom will in the output, include a
'Volume size' number. For example, say it's 1000

dd if=/dev/dvd bs=2048 count=1000 | md5sum -

That md5sum should always match the iso file that was used to burn the cd.

None of this matters in John's case, however, since all he did was copy
the file from one hard drive to another, in which case, the md5sum
should absofuckinglutely not change. Either the thumb drive is
defective, or one the pc's has bad ram, or is corrupting data in the IO
path.



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Old 11-03-2009, 02:55 AM
James Michael Fultz
 
Default Jaunty Jackalope (RESOLVED)

* NoOp <glgxg@sbcglobal.net> [2009-11-02 19:32 -0800]:
[...]
> And I've just now proven myself wrong :-( The md5sum of the CD matches
> that of the iso. So apologies to the list, and to John Graddy. I'll
> still see if I can find the thread tomorrow, but mea culpa & apologies
> to all.

Well, at least you've gotten me onto something I need to investigate.

Experience has told me that the MD5 has should match for all copies of
an error-free download, file copy, and CD burn. I was going to
demonstrate this when I found that they didn't for my copies of
Ubuntu 9.10 64-bit which I'd downloaded using BitTorrent.

$ wget -q -O - http://www.gtlib.gatech.edu/pub/ubuntu-releases/karmic/MD5SUMS
[...]
dc51c1d7e3e173dcab4e0b9ad2be2bbf *ubuntu-9.10-desktop-amd64.iso
[...]
$ md5sum -b ubuntu-9.10-desktop-amd64.iso
82a867bbfe856e50f4dcec9d7585193c *ubuntu-9.10-desktop-amd64.iso
$ md5sum -b /dev/cdrom
f20000abc83e2b07cff2e1e6bddf44d3 */dev/cdrom

What on earth?! Yes, I've checked another mirror as well. Also
downloaded the .torrent file again, and Transmission verifies the ISO
100% complete.

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