Re: [Plug] That idiotic cylinder 1024 problem

[Michelle Weber <umweber@mcs.drexel.edu>]

Does this problem only exist in linux? Or does it affect other operating
systems as well?


--
Michelle Weber
umweber@mcs.drexel.edu


On Thu, 4 Nov 1999, Mark-Jason Dominus wrote:

>
> If you try to use LILO to install a boot block, it sometimes says
>
> 	geo_comp_addr: Cylinder number is too big (<number> > 1023)
>
> That means that part of your /vmlinux file is stored in a block that is
> on the wrong part of the disk, and the BIOS will not be able to load
> the /vmlinux at boot time.
>
> What can you do about this?  Basically, nothing.  The helpful
> documentation helpfully says
>
> 	Try moving the file to a different place, preferably a
> 	partition that is entirely within the first 1024 cylinders of
> 	the disk.
>
> Now how are you supposed to do that?  If you knew about this in
> advance, you already have a disk partition at the front of your disk
> which is no more than 1024 cylinders.  But in that case you don't get
> this error message in the first place.  But you did get it; what do
> you do now?
>
> Well, you can go onto IRC and ask for advice and listen to someone
> tell you that you should have studied the docmuentation more carefully
> before you began.  When I become Emperor, those people will live in
> the oubliette.
>
> Let's see, what else? I guess you can dump all your files to tape an
> repartition your entire hard disk and then try to figure out how to
> hook the two partitions together to get the same file structure you
> had before.  Maybe next time you won't be foolish enough to dare to
> try to boot from a disk with more than 1024 cylinders.
>
> I ran into this problem last week, but I was lucky.  I had just bought
> a new disk and I could partition it any way I wanted to.  So I got
> around it by making a little tiny partition on the new disk, with only
> 32 cylinders and nothing on it but the kernel files and the boot
> stuff.  I mount the little partition on /boot.  If I had not happened
> to have just gotten back from the store with a new disk, I would have
> been entirely hosed.  And what a stupid thing to have to do anyway.
> At the PLUG meeting yesterday I was amazed.  Someone told me that this
> stupidity is a *recommended configuration*.
>
> I had planned to ask about the 1024 cylinder thing yesterday when I
> got to the meeting.  I didn't have to.  A whole lot of people were
> talking about it when I got there.  Today Adam told me about someone
> who can only boot his Debian system from floppy because his vmlinux is
> in the wrong place.
>
> I think I've solved this problem.  I wrote a program that locates some
> `good' blocks (the ones on cylinders 0-1023) on your boot disk and
> copies your kernel file into them.
>
> I tried it out.  It worked just fine for me.  My four kernel images
> are all bootable now, and I don't need the mini-partition.
>
> I have not tested this program adequately.  It is very difficult to
> exercise all the code paths for this program.  I cannot guarantee that
> it won't do something terrible.  It might corrupt your vmlinux file.
> It might decide that there are some good blocks in /bin/bash and that
> it is going to reclaim them, and accidentally corrupt or erase your
> /bin/bash.  There are probably the worst case-scenarios.  I will keep
> working on this, but I would like some brave volunteers to help me
> with it.  I thought there might be some people on this list with
> unbootable systems who would want to give it a try in spite of the
> risk.
>
> The prototype of the program is in Perl.  I have a C version under
> construction but I may abandon it because the prototype is working
> well enough.  Access to a C compiler is desirable, however, because
> the program uses the C compiler to get some configuration information
> that it needs.
>
> If you are desperate enough to want to try out this useful but risky
> and untested program, send me mail.  It is named `soliloquy', and you
> should send me mail at mjd-plug-soliloquy@plover.com.
>
> Mark-Jason Dominus 	  			               mjd@plover.com
>
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