Re: Windows multiboot (aaargh!)
On Sunday 14 September 2003 12:39, Pigeon wrote:
> On Sat, Sep 13, 2003 at 04:33:22PM +1200, cr wrote:
> > On Thursday 11 September 2003 09:38, Pigeon wrote:
> >
> > (preliminaries snipped)
> > The Linux boot floppy is a bit more tricky. I thought I'd better first
> > delete the existing Linux partitons on the drive using cfdisk rather than
> > DOS fdisk. So I tried adding cfdisk to a spare Debian Woody boot
> > floppy, but it got 'kernel panic' when run. Tried same with a RH boot
> > floppy and it worked OK (I think the hard drive had RH7.3 on it, IIRC),
> > but got 'kernel panic' when I used it after wiping the hard drive.
> > Obviously Deb and RH boot floppies are just intended for booting the
> > system on the hard drive.
>
> Dunno about RH; the Debian one seems to want you to supply it with a
> root filesystem from somewhere, either your existing installation or a
> second floppy.
I'd say RH does exactly the same.
It'd be nice to have a self-contained floppy with just the basic componenets
needed to boot a Linux system, so there's room to add a few utilties of ones
choice. I've done that with my DOS floppy. But reading the HOWTOs, it
seems that creating a Linux boot disk is a rather more complex procedure.
I guess the workaround is to use one of the pre-made disks like tomsrtbt, and
just put my own utilities on a floppy that I can mount afterwards. At
least, unlike DOS-booted-from-a-floppy, I imagine the Linux rescue systems
don't constantly nag you to "Insert disk with COMMAND.COM in Drive A:" or
whatever the Linux equivalent would be ;)
> For blanking things, I use dd; to zap the whole MBR
>
> dd if=/dev/zero of=/dev/hdx bs=512 count=1
>
> and for just the partition table
>
> dd if=/dev/zero of=/dev/hdx bs=1 seek=446 count=64
> > I tried Googling for how to create a boot floppy, what I found was
> > several rescue disks - Tomsrtbt, RIP and Leka - all of which downloaded
> > quite nicely, installed themselves onto floppies exactly as per
> > instructions, and work very well. They all have fdisk (but not cfdisk).
> > I can recommend them to anyone reading this, as a useful tool to keep
> > handy. But as they're so compressed I can't put anything extra on
> > them. I suppose I could put cfdisk on another floppy and run it from
> > that after Toms/RIP/Leka are running in RAM.
>
> The man page for fdisk says it's basically "a buggy program that does
> fuzzy things but happens to produce reasonable results", and
> recommends using cfdisk instead.
>
> For a boot floppy with cfdisk on it I use the resc1440.bin boot floppy
> image off the Debian Slink installation CD. Unlike the Woody boot
> image, it doesn't require a root filesystem supplied from another disk.
I had a look on my various Linux CD's, and a look at Debian.org, but I
couldn't find it. OTOH I may have missed it. I'll try putting cfdisk on
a floppy and running it from that, after booting with a rescue disk.
Umm, just tried, with Leka's system running and a DOS floppy in the drive.
mount -t msdos /dev/fd0 /floppy
mounting /dev/fd0 on /floppy failed: no such device
But it's got a /dev/fd0 there, I checked. I'm probably forgetting
something important. Ah well, fdisk it is ;)
> > > - Boot DOS, and partition /dev/hdc with one 500MB primary DOS
> > > partition (for your DOS boot partition), no other partitions.
> > > - Boot Linux, and use cfdisk to change the partition type of that
> > > partition to something DOS doesn't recognise.
> >
> > As a matter of interest, fdisk doesn't have 'DOS' or 'ext2' in its list
> > of filetypes - I assume 'FAT16' and 'Linux' are the equivalents.
>
> This would seem to be the case. The numeric IDs are 06 and 83.
>
> <snip peculiar symptoms>
>
> > Some thought is indicated. I may save this drive for Linux use (with
> > which it works fine) and pick up another drive for my experiments.
>
> This is most unexpected... I grabbed a spare PC and HD from my latest
> dumpster-diving expedition and experimented. The HD was only 2 gig, so
> I reduced all the partition sizes by a third. Got the same result...
> FDISK showing partitions swapped, and the second partition starts
> "trying to recover allocation unit xxx" part way through where x >=
> 25000 or so.
Umm, but does this weird behaviour start at the same distance into the
physical drive, or the same distance into the second partition, or the same
percentage in?
> Tried changing the procedure slightly - formatted the DOS partitions
> immediately after creating them and before hiding them. This time they
> all went OK, but at the end of the procedure FDISK was showing
> partitions swapped, one of the volume labels had disappeared in FDISK,
> and one of the previously-correctly-formatted partitions gave me
> "invalid media type" at the prompt.
>
> At this point I changed the method of hiding partitions; instead of
> booting the slink floppy and using cfdisk I used Norton Utilities
> under DOS, because it's a whole lot quicker than waiting for the Linux
> boot floppy to load.
>
> I zeroed the partition table and started again, rebooting not only
> after each FDISK but after each FORMAT and each Norton edit. When it
> came to creating the DOS and ext2 extended partitions, I created two
> DOS partitions instead. Rebooted and checked what I'd got - at this
> stage all was fine.
>
> Started NU, and changed the type of the second extended partition to
> Xenix (just as good as ext2 for the purpose, and easier). Rebooted...
> and FDISK showed partitions swapped, previously good partitions gave
> "invalid media type", etc. Changed it back, and all was well again.
> Trying it with the first extended partition gave a similar result.
>
> Conclusion: DOS can't cope with the presence of non-DOS extended
> partitions. How dead and chewed.
>
> So it seems that the options are something like:
>
> - don't have a Linux partition on that drive at all
> - don't have your second DOS partition, so there can be room for the
> ext2 partition to be a primary partition
> - have two extended partitions, both DOS, and use umsdos in one of them
Let me see - umsdos (and support for it is in my kernel, I just checked)
will allow long filenames to be used *and* DOS can still read it, is that
right?
I was intending to use the Linux partition as temporary space for mkisofs to
put CD images for cdrecord to write to CD. It's handy to reserve a spare
space of the right size that won't get imperceptibly filled up. I suppose
the question now is whether mkisofs and cdrecord can work with umsdos.
If not, no disaster, I'll just have to find 800MB somewhere else on the
system.
I thought DOS could only handle partitions of up to ~500MB (512? 528?). I
must be wrong, it happily formatted 600MB, at least for partition 3.
But anyway, this is the revised scheme:
1 Pri DOS 500MB Bootable DOS6.22
2 Pri DOS 600MB W95
3 Pri DOS 600MB W98
4 Extended 5 DOS 500MB
6 DOS 800MB
I'll see how it goes.
3 may get converted to FAT32 later.
> It also seems I'd misremembered how the drive letters get allocated;
> as you found out, the bootable primary partition is C:, the extended
> DOS partition(s) come next and after them the other primary DOS
> partitions.
Does that sound like it spells 'kludge' ? ;)
There's actually a file in the Microsoft Knowledge Base that explains how
letters are assigned... if you have multi drives and multi partitions it
gets fiendishly complicated.
> > > To switch between booting different OSes, two methods are possible:
> > >
> > > - (Easy, but unsmooth) Use Norton Utilities (for DOS) to edit the
> > > partition table and set the "bootable" flag on the partition for the
> > > OS you want to boot. From within Win95/98, set the shortcut to
> > > Norton to "run in MS-DOS mode".
> > > - (Not so easy, but smoother) write a program to set the appropriate
> > > "bootable" flag as you instruct and then reboot. For example, you
> > > could have it accept as a command-line parameter the OS you want to
> > > switch to, and then "reboot 95" or "reboot 98" from within DOS, or
> > > in 95/98 set a couple of shortcuts with the appropriate command-line
> > > parameter and "run in MS-DOS mode".
> >
> > Or, could I just use Linux fdisk?
>
> Yes, although you'd have to reboot twice...
>
> In fact, you can use DOS FDISK as well... why is it that I've been
> tweaking bootable flags for years and never tried using DOS FDISK
> until tonight? Seems to work OK. Brain the size of a peanut strikes
> again.
And I've been using FDISK too, yet I spent some time googling around in the
recesses of Simtel trying to find a utility to do just that.
"Why didn't we think of that?"
"Guess our brains must be too highly trained"
(apologies to DNA)
> > (much snippage)
> >
> > > It is also possible to boot Linux from within DOS/Windoze using
> > > LOADLIN.EXE (again "run in MS-DOS mode") without actually rebooting.
> >
> > I was thinking of trying that later, though I was unsure about how stable
> > it might be. But quite by chance, I found that the install for the DOS
> > zip version of Tom's Root Boot does exactly that - when unzipped (in
> > DOS), running 'install.bat' immediately uses loadlin to start its own
> > little Linux system to create the floppy. And it *all*, Linux system
> > plus floppy contents plus HTML faq, comes in a 2.2MB zip file. Tom
> > must be a fanatic at squeezing the maximum stuff into the tiniest
> > package.
>
> Linux happily wipes out all trace of the previous operating system,
> and carries on as if booted straight from the MBR. When I first
> installed Debian, I balked at the possibility of LILO screwing up my
> time-consuming MBR hacks, and set it up to boot using LOADLIN. Then,
> when I first recompiled a kernel, I cocked it up, and experienced no
> trouble at all in reverting to my previous kernel just by editing the
> LOADLIN batch file. What I'd read so far seemed to indicate that LILO
> was a bitch to use and fraught with danger, whereas my experience of
> LOADLIN was that it was a doddle to set up and to recover from
> disaster. So I've never bothered to change - I just set up a 50MB DOS
> partition at the start of the HD with the DOS editor, LOADLIN and a
> history of kernels and kernel boot config files. Works fine.
Well, I've found that GRUB is extremely benign (once sorted). It took me a
while to sort booting on this thing, I suspect mainly because GRUB reads the
BIOS drive type and I had that set wrong (and IIRC Linux doesn't, so once
booted from floppy(!) it was fine). But GRUB has since happily handled two
changes of kernel without a hitch. It pops up a menu to allow me to choose
which kernel to boot.
>
> If you have a PS/2 mouse and it doesn't work after booting out of
> Windoze with LOADLIN, try "echo -ne '\377' > /dev/psaux" before
> starting X. This works around a bug in X which was fixed some time
> between 4.2.0 and 4.2.1.7.
No, my meeces are all plain vanilla 9-pin serial
cr
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