On Monday 26 November 2007, Bill Davidsen wrote: >Gene Heskett wrote: >> On Friday 23 November 2007, Andre Robatino wrote: >>> 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. >> >> I was under the impression that is backwards, and that the readahead was >> finding the end of the iso ok, but was handing the trailing garbage from >> the previous read buffer to the summer, so it was getting an extra few >> hundred bytes instead of a valid EOF at where ever the good data ended in >> the buffer. This would be caused by an incorrect EOF checking sequence. >> >> Also, please note that when dd is given the exact number of blocks of size >> 2048 to read, dd reports no EOF error, and the checksum is correct, so it >> makes no sense to me that the actual is smaller than the iso. That is not >> to say that the iso doesn't have some trailing zero padding applied in >> order to make it an even *2048 in size, but that is not and never has been >> an error. The sha1sum (or md5sum) isn't effected by zero fill padding >> AFAIK. >> >> All that said, if that script works folks, use it. Or shut readahead off >> in your kernel builds. > >That's a bit drastic! You can set it to zero with "blockdev --setra 0" >instead, just when you want to verify something. I wasn't aware it might be that simple. Thanks. Does that indeed fix the problem, Bill? Just Curious(TM). :) >-- >Bill Davidsen <davidsen@xxxxxxx> > "We have more to fear from the bungling of the incompetent than from >the machinations of the wicked." - from Slashdot -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) He jests at scars who never felt a wound. -- Shakespeare, "Romeo and Juliet, II. 2"
