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Re: sha1sum problems :-(



Andre Robatino wrote:
Marko Vojinovic wrote:
Ok, I downloaded the brand-new Fedora 8 iso file:

[vmarko sith ~]$ sha1sum Fedora-8-i386-DVD.iso
782a0e80de1b8e9f24e10e40055cc1b545390cbd  Fedora-8-i386-DVD.iso

After burning it to two dvd's on two different machines (one Windows, the
other Linux) using different software (Nero and K3B), I get:

[vmarko sith ~]$ sha1sum /dev/dvd
04e39c4be1cf577b98a8b94ff61bdb60252ec6cb  /dev/dvd

"sha1sum /dev/dvd" is not a reliable way to read a disc, though it may work on some hardware. Try using the rawread script at

http://www.troubleshooters.com/linux/coasterless.htm

instead. This uses the isoinfo command to determine how big the ISO file is, then runs a dd command that attempts to read exactly that much off the drive. If this still fails, then please report back. I'm currently seeing a return of the old mediacheck problem (linux readahead bug).

I had the idea that this problem had been fixed[1], as I suspect you do also. I haven't seen it recently, but having gotten into the habit of using dd to check only what I expect to write, I wouldn't have seen it in every case. The old solution was to turn off readahead, I tried that recently, but there really *was* a problem in my case.

I no longer expect an error at end of data, and I don't use the noerror option to dd because of that.

[1] on a last read shorter than the readahead, I think you get all of the data actually read and no error. Certainly the data doesn't appear to be truncated on error any more AFAIK. However, depending on how the data was padded, you may get some data which really *is* on the DVD and is *not* part of the ISO image.

--
Bill Davidsen <davidsen tmr com>
  "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot


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