[NTLUG:Discuss] iso md5sum question

[Robert Pearson]

On Sat, Nov 8, 2008 at 6:45 PM, Fred James <fredjame at fredjame.cnc.net> wrote:
> ./aal wrote:
>> On Sat, Nov 8, 2008 at 4:43 PM, Wayne Walker <wwalker at bybent.com> wrote:
>>
>>> On Sat, Nov 08, 2008 at 04:21:16PM -0600, Fred James wrote:
>>>
>>>> All
>>>> I downloaded ubcd411.zip, unzip'd it to ubcd411.iso and ran md5sum
>>>> against it ...
>>>>     md5sum ubcd411.iso returned a number identical to the one posted on
>>>> the web site
>>>>     md4sum --check ubcd411.iso returned this message ...
>>>>
>>> md5sum --check MD5SUM
>>>
>>> --check takes an argument of a file fulle of md5sum output lines to match,
>>> not the name of a file to test.
>>>
>>>
>>>> "md5sum: ubcd411.iso: no properly formatted MD5 checksum lines found"
>>>>
>>>> What am I looking at?  Thank you in advance for any help you may be able
>>>> to offer
>>>> Regards
>>>> Fred James
>>>>
>>
>> there should be 2 files on the site you get your iso from
>> file.iso               the disk image to burn
>>
>> file.md5sum      a text file containing info for md5sum to use
>> or
>> file.DIGEST(S)
>>
>>
>> here is what to do with them
>>
>> put the iso and the md5sum/DIGEST file in the same directory
>> run this command to check
>> md5sum -c file.md5sum  (or file.DIGEST depending on what you have)
>>
>> then you will get a simple pass/fail output
>>
>>
>> and
>> read the manpage for md5sum
>>
>>
>>
>> hope that helps
>> ./aal
>>
> ./aal
> So the problem is that the download site provided an md5 number, not a
> file?  Actually, the md5sum files that I have seen contain (on one line)
> the md5 number and the iso filename - so I put the number provided into
> a file followed by the iso filename, but md5sum -c returns the same
> error as before.  Should I trust the file since the check sums are the
> same, or is md5sum -c telling me otherwise?  Thank you in advance for
> any help you may be able to offer
> Regards
> Fred James
>
>
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>

There is something wrong with your MD5SUM text file.
There should be an ISO file for each image at that URL. There will be
a text file containing the MD5SUM's for all the images.
Some times I just cut and paste the MD5SUM file contents to a local
text file. Other times I download the text file.
The format of MD5SUM files seems to vary. Sometimes I have to adjust
the contents of cut and paste or downloaded.
Not the MD5SUM number.
Sometimes the file name in the MD5SUM file extension is different than
the one downloaded.
Sometimes the position in the line is wrong.
Sometimes there is extra information in the file that my version of
MD5SUM will not process.
It does not seem to be a perfect world but it does work if you read
the "man" pages or Google md5sum usage.

The process is to trust the MD5SUM number generated by the download
site and normally in their MD5SUM text file.
Re-computing it locally and manually comparing the two is one way to
do it but more error prone than having the MD5SUM program do it.
I use K3b to burn with and it computes an MD5SUM and allows you to
enter a comparison number. Usually I check after download and again at
burn time. I also run "media check" at install time. These checks have
saved me a lot of time.

If the MD5SUM's do not match it saves your time making a disc coaster
and trying to install it.