file integrity fails LXFDVD155

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file integrity fails LXFDVD155

Postby steve_usa_2011 » Fri Feb 03, 2012 8:20 pm

Hi everyone,
I downloaded the 155 iso via the torrent and performed the "check local data" feature with success. Running an md5sum produces a different number than the hash that was on the torrent. Next, I burned to dvd and when completed, tried a check disc, which failed with the message: "The file integrity check could not be performed. No checksum file could be found on the disc." Please note that I did the same last month for 154 with the exact result. When the real LXFD154 arrived it passed the disc check.

My questions as a newbie are:

1 Am I not doing something I should?
2 Why is there a difference between the two DVDs?
3 Why is my md5sum different from the torrent hash?

Thanks a bunch, having fun, mostly!
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Postby heiowge » Sat Feb 04, 2012 8:24 am

I think you should have stopped when the md5 sum differed! Those things are there to tell you if you downloaded it completely and without errors. Since they were different, I'd have deleted it and started over. If you had the same error a second time, I'd have reported it to the site owners.
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Postby ajgreeny » Sat Feb 04, 2012 9:51 pm

Having used a torrent to do the download, everything should have been fine, as torrent clients check the packets as the arrive. It seems to me that the source file at the server end must be corrupt, or they have made changes to it but not also changed the md5sum.

However, you talk about the "different number than the hash that was on the torrent" and I wonder if you ran an md5sum on the torrent file itself, which will be different to that of the .iso file.
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file integrity error on dvd

Postby steve_usa_2011 » Sun Feb 05, 2012 12:24 am

Thank you for your willingness to help me. This is my first forum experience and it was a fearful thing for me.

When the iso downloads completed (both 154 last month and 155 recently) I used the check local data option when torrent finished and did not get any type of errors.

I did indeed run the md5sum on the 154 and 155 iso files, and compared those results to the hash shown on the torrent (I suspected I could be using the wrong items to compare but saw no other options).

After burning the DVDs using brassero, I selected the check disc option from the right-click drop down menu on the LXFDVD icon on the desktop.
This is where I got the file integrity errors.

When the Coverdisc in issue 154 arrived (2-3 weeks after on sale), I was able to run do the exact same check disc procedure but with success. LXFDVD155 has not yet arrived so I cannot confirm the same as 154 but I will test it when it lands in my mailbox.

I did in fact, do 154 over with the exact results noted.

How then to find the difference between DVD 155 when it arrives? Unfortunately, I got mad at 154 and deleted the iso and shredded the DVD before I worked up the courage to ask for help.

Again, much appreciation for your time and thoughts!
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Postby nelz » Sun Feb 05, 2012 11:21 am

If the ISO passes the checksum test but the burned disc does not, it could be the medium you burned it to at fault.

Another possibility, I'm not certain of the procedure involved in the check disc option on the desktop, is that this is a hybrid ISO image, one that boots from DVD or USB stick. This contains extra information at the end of the file that is discarded when written to a DVD (that's why the dvd2usb script is necessary to replace it if you want to copy the DVD to a USB stick). If the check process you use compares the disc to the original ISO, I would expect it to fail because of this and such a failure is not a problem in itself.

As long as neither the torrent download nor the burning process report errors, you should be OK.
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file integrity fails

Postby steve_usa_2011 » Tue Feb 07, 2012 8:03 pm

Great advice1 Sorry for the delay in responding, I was trying different media. Various dvd formats (+R, -R, RW) did not fix the problem (on either PC), but may have led me to a solution ( have not had time to try, but I shoud know by tomorrow). I even tried a different PC with Centos, rather than Ubuntu, (and K3b and Gnomebake burn programs) but I get the exact same results on both.

Since I did not have an md5sum (from LXF towers) for the iso, I could not be sure that the file on my PCs were in fact legit, so I downloaded a similar size iso from ubuntu via torrents to both PCs and check their md5sums against the ubuntu supplied md5sum file with a match in both cases. This made me think of the common traits of both machines -- at least those I suspect. They are:
Brasero - opens when I insert a blank DVD, then I opt for "write to disc"
TSST SH-S203B and SH-S203N (your media hint led me here)

In the past, when I ran the "check disc" utility on a bona-fide LXFDVDxx, it was successful. So maybe by DVD burner can correctly read, but not write, the DVD. I even borrowed on burner from my neighbor but with the same results. If you havent guessed by now, it was also a TSST brand but model SH-223. (I even tried to flash the firmware on my 203N with the SB01 (downgraded it from SB02) firmware).

Thats where I am just now. I acquired another Burner, a Lite-on model iHAS124-04 B which I will install and try with results to follow.

Still having fun, and am learning alot, thanks!
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Postby nelz » Tue Feb 07, 2012 9:11 pm

Torrents include checksums for the files that are checked at the end of downloading. If the download completes without an error, you can be confident the files have not been corrupted in transit.

The fact that the check worked in the past makes me more certain it is the hybrid ISO format at the root of this, this was introduced for DVD 154.
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file integrity fails

Postby steve_usa_2011 » Wed Feb 08, 2012 1:51 am

I have finished some experiments and have mixed results, Here goes!

I installed the Lite-on dvd burner in the ubuntu LTS box. I burned both -R and +R DVDs from the previously used ubuntu iso file (4.2 GB). Both completed without errors and both failed when I tried the "Check disc" utility. (When the DVD is ejected after burn and re-inserted an icon is placed on the Desktop -- a right click from the mouse opens a menu -- and Check disc is chosen). This program fails with the "File integrity could not be performed. No checksum file could be found on the disc."

Next, I pursued the OS/Desktop path and put a Live Puppy Linux 5.2.5 CD in and booted to it. Mounted the hard drive for access to the same iso and burned it to both a -R and +R DVD using Pburn 3.34. When completed, each asked to perform an md5sum, which I accepted and they both were identical to each other and to the iso. After that I opened Console and did an md5sum on /dev/dvd, which produced the DVD checksum, and again both DVDs matched each other. Then I tried one of the previously failed DVDs from the stack of supposed coasters and when it completed, the number was the same as the two I just burned (I was carefully marking the DVDs with the burner mfg, which PC, and the iso used, so I am sure). Now all that seemed to be left was to reboot to ubuntu and try the 3 DVDs I just tested in Puppy. All 3 failed the "Check Disc". Hmmm, Ahaaa, and Yikes!

My conclusions (sparse and probably not the whole answer) are that something in either Centos 6 or Ubuntu LTS, and their Desktops may be the problem since Puppy and Pburn performed admirably. Now I don't know what I want to do about it (aspirin did help some) since I cant find a Pburn in my package manager and am not even sure it would work. Maybe it is a good time to move from ubuntu. Puppy will forever be in my arsenal of go to troubleshooting media.

Any more thoughts about this are gratefully received, and thanks again for you indulgence.

Still havin' fun and learning alot!
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file integrity

Postby steve_usa_2011 » Wed Feb 08, 2012 3:21 am

Tried to test the hybrid ISO theory by running the "Check disc" utilty on one of the last "same in both checksums" ubuntu iso files and it failed as all the others. I checked the real LXFDVD154 and it passed, go figure.

Booted to the Live Puppy again and ran md5sum from console and then booted ubuntu and ran the same md5sum from terminal and both results matched. So it seems from my previous tests that I am burning the exact data in both Puppy and Ubuntu and probably Centos (didn't retest it), but only Ubuntu and Centos have the problem with the DVD file integrity check.

Possible bug in whatever process writes iso files in Ubuntu LTS and Centos 6? As pointed out by nelz, is it the way the hybrid iso format is handled by those systems or drivers for the burner?

Still having fun, and definitely learning a bit at a time!
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file integrity

Postby steve_usa_2011 » Wed Feb 08, 2012 10:31 am

Ooops, I meant reads the iso image on the disc.

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file integrity

Postby steve_usa_2011 » Wed Feb 08, 2012 5:49 pm

The real LXFDVD155 arrived today. I ran the "Check disc" as usual, and it passed. I ran the dvd made from the downloaded 155 iso and it failed as before. Next I ran md5sum /dev dvd on both and got identical results.

So it seems my system can write it correctly to the dvd but does not read the same as it reads the original DVD.

Now I am lost but good. More help please.


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Postby nelz » Wed Feb 08, 2012 7:22 pm

The real DVD and a DVD-R burned from the ISO give the same md5sum but the downloaded ISO is different? A hybrid ISO image has extra bytes on the end which are not written to the disc, which would explain the discrepancy.

It you do
Code: Select all
cp /dev/dvd fromdvd.iso
and then ls fromdvd.iso and the downloaded ISO, is the former a couple of hundred bytes smaller?
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file integrity

Postby steve_usa_2011 » Wed Feb 08, 2012 9:31 pm

I did as you instructed and the fromdvd.iso and the 155.iso are the same size -- 4379901952. I then did the same with the DVD which came with the magazine and it was also the same size as the previous two.

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file integrity

Postby steve_usa_2011 » Wed Feb 08, 2012 11:28 pm

I am still pursuing your hybrid iso diagnosis. When I open Brasero 2.30.2 and select tools, there is a Check integrity option in the menu which gives me the same window and same error result as I have been experiencing. I tried to update it via synaptic but it has no selection for any newer version. Upon visiting the Brasero web site, they have version 3.0.0 stable available, but only as a *tar.bz2. I have extracted it, but am still trying to install it.


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Postby Ben » Thu Feb 09, 2012 11:06 am

Hi Steve,

I've just had a go at re-creating your problem, and I'm a little unsure of the exact process you've followed.

As a few people have mentioned, the bit torrent contains it's own integrety checks to ensure that the file you download is the same as the file on the server. What you can use MD5 sums to check is that the downloaded file is burned onto the DVD correctly.

To do this, the first thing you need to do is create an MD5sum of the ISO file using the command:

md5sum 155.iso > 155md5.txt

This will create a file 155md5.txt containing the MD5sum of the ISO. You can then use this to check the disk. In Brasero you can go to Tools > Check Integrity. This will open a dialogue box. In the top half you can select the disc you wish to check, and in the lower half you can select the MD5sum file. Note that unless you select an MD5sum file, the process will error if the Use an MD5 file to check the disc box is checked.

Select the disc you want to check and the 155md5.txt file created above and run the checks.

If you get an error about permissions, you probably need to unmount the disc. You can find out the device by running

df -h

then unmount it using:

sudo umount /dev/sr0

where /dev/sr0 is the DVD device displayed by df-h. You should then be able to perform the check.

Hopefully that should run correctly, if not let me know which point it has failed at.

Cheers,

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