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RE: RedHat 6.1 installation reboots before writing partitions



Hi folks,

Once again:

> > Ok, I've been spending a little time at the RedHat site.  
> > First, I don't know
> > where the "8GB limit" came from.  
> 
> neither do I, tho from experience I know it exists.

> > The only thing I've found is that LILO has a
> > limitation imposed by the BIOS that says 
> > everything in /boot must be below cylinder 1023 
> > It also mentions that some newer BIOSes don't 
> > have this 1023 limitation, so it's not LILO 
> > but the BIOS.

 Until very recently BIOSes used 24 bits to address the sectors on a hard 
disk, 10 for cylinders (0..1023), 8 for heads (0..255) and 6 for sectors (1..63) 
(CHS). I am not going into detail about the fact that this is a virtual 
addressing scheme, in the sense that these numbers have nothing to do 
with the actual number of heads, cylinders and sectors (well, they did in the 
stoneage of 40 MB drives).
 Since sectors on all harddisks contain 512 bytes, this gives you a BIOS 
addressable space of 1024 x 256 x 63 x 512 bytes, which is just a little 
less than 8 GB. Since lilo needs the BIOS to access the drive(s) - no 
operating system with its own calls to access drives is loaded yet at boot 
time - it is bound to this limit. Linux and (some) other operating systems 
use their own calls to access drives. On my system for example, I have a 
10 GB drive, of which Windows 95 sees only 8 GB, but linux ignores the 
BIOS, and can therefore use the whole drive.
 As long as you make sure that there is a /boot partition below the 1023rd 
cylinder you can use the rest of the drive for other partitions.
 About the rescue disk: Well, in the /images directory on the CD there used 
to be an image rescue.img next to the boot.img and bootnet.img, which is a 
small filesystem with some basic tools, like fdisk. It was there in RedHat 
3.03, 5.1(, 5.2?) and 6.0, but it disappeared in RedHat 6.1 (and 6.2). I didn't 
notice this until now, and I don't know why they threw it out. Seems like a 
dumb move to me. You will have to download both boot.img and rescue.img 
for 6.0. It is no problem to use these images if you just want to test the 
installation, but don't use this boot.img to install 6.1.
 You can create the floppies from the images in two ways: with linux use 
dd. This should look something like: dd if=/somewhere/boot.img of=/dev/fd0. 
Substitute the correct path for the image and the floppy drive. You can also 
create the floppies with the DOS utility rawrite. See the directory dosutils on 
the CD.
 If you type "rescue" on the boot prompt after booting with the boot floppy, 
you are prompted to insert the rescue disk after a while. You now have a 
small linux system running with which you can run simple commands like 
mount and fdisk.
 Finally some words on fdisk. Afaik the DOS fdisk just adds a new partition 
right behind the existing ones. I am not 100% sure what it does if there is a 
gap, but it probably tries to fill this first. The linux fdisk utility is more 
flexible: You can specifiy the start cylinder of the new partition. This way 
you can reserve space for other partitions (f.e. if you want to reserve some 
space below 8 GB).
 Well, enough for now,

					Ciao!

					Leonard.



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