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Re: mediacheck failing ...



Gene Heskett wrote:
On Friday 23 November 2007, Andre Robatino wrote:
David Timms wrote:
Andre Robatino wrote:
Andre Robatino wrote:
 I'm pretty sure that it was fixed, or at least less likely to
manifest.  I was using the same computer, with the same DVD drive,
when F7 came out, and found by going through a pile of old Fedora
CDs that I burned without padding that all of them passed mediacheck
anyway, though many of them failed earlier.  Testing now with F8, I
find that 3 out of 3 of them fail (I was convinced at that point and
stopped checking).
 Just to clarify, the mediacheck I'm talking about is checkisomd5
from the anaconda-runtime package, which is the equivalent of the
regular mediacheck, but done while booted up in a currently installed
Fedora.  So my mediacheck was using the kernel in the distro being
used at the time (F7/F8), not the kernel on the old install discs
themselves, as would have been the case if I booted from them.
http://docs.fedoraproject.org/release-notes/f8/en_US/sn-Installer.html
find mediacheck

This suggests certain hdparm parameters get applied when you boot the
dvd and start linux mediacheck, this wouldn't happen if you are
running from a live f7/8.

Also there is suggestion to try:
ide=nodma mediacheck
in https://bugzilla.redhat.com/show_bug.cgi?id=177526

Does either make any difference ?
 I thought that using the word "mediacheck" only caused the installer
to go to the mediacheck immediately, instead of asking first, so we only
tried the "ide=nodma" option, which didn't help.  The latter, at least,
is definitely not a reliable workaround, but applying the proper
zero-padding seems to be.  Even if the ide=nodma works, one has to
remember to use it during the actual install, not just the mediacheck,
then to remove it from grub.conf later, since any options used during
install end up there.

As has been stated here before, the only reliable way to do the mediacheck once the disk is burnt, is to call up something like kcalc, enter the size of the iso image as it sits on your hard drive, and divide by 2048, the size of a 'sector' on a cd/dvd. Then use the answer as the count= in a command line to dd that looks something like this:

dd if=/dev/dvd0 bs=2048, count=answer-above|sha1sum

Then a readahead bug doesn't have a chance because you are only reading exactly the size of the .iso image.

 I always use the rawread script from

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

which does all this automatically. The readahead bug prevents the last tiny little bit of the ISO at the end from actually being read, so knowing how big the ISO is supposed to be doesn't help since the part that's readable is smaller than that.

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