Messages in this thread | | | Date | Fri, 06 Dec 2002 12:45:20 +0100 | From | Edgar Toernig <> | Subject | Re: Unable to boot a raw kernel image :?? |
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DervishD wrote: > > Hi all :)) > > A time ago I was able to generate bootable Linux CD's just by > dd'ing a floppy containing a raw kernel image: > > dd if=/dev/fd0 of=eltorito > > After that, mkisofsing, toasting and booting. But now, depending > on the machine, I have 'invalid compressed format' errors, or even > ye olde register dump when the image was damaged :( > > Booting directly from the floppy works, but booting with that > same image from a CD does not :(( I now I can use LILO, or better > yet, Syslinux or isolinux, but I'm just curious why I cannot boot raw > image-based CD's anymore. > > Anyone knows what's happenning here?
I had this problem a while ago. It turned out to be a (widespread) BIOS bug triggered be the disk-size probe of the kernel's boot loader.
The crude fix which worked for me: disable the probing for 2.88MB disks by changing the first byte of the disksizes table at the end of bootsect.S from 36 to 18.
The long explanation: The BIOS allows bigger-than-track-size reads in El-Torito mode which confuses the probe routine which then assumes a 2.88MB disk when the BIOS is actually emulating a 1.44MB disk. In LBA mode that would be no problem but in CHS mode (which is used by the loader) it does not work.
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