Re: Windows multiboot (aaargh!)

From: Pigeon (jah.pigeon_at_ukonline.co.uk)
Date: 09/14/03

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    Date: Sun, 14 Sep 2003 22:20:02 +0100
To: debian-user@lists.debian.org

    On Sun, Sep 14, 2003 at 09:23:47PM +1200, cr wrote:
    > On Sunday 14 September 2003 12:39, Pigeon wrote:
    > > On Sat, Sep 13, 2003 at 04:33:22PM +1200, cr wrote:
    > 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.

    And the kernel takes up half the disk, so there's less space for the
    utils.

    CD-ROMs are easier, it seems (if the box can boot them) - I've even
    made a bootable Linux CD in Windoze - a mate was playing with his new
    Nero and wanted to try out the facility for making bootable CDs, so we
    fed it a Linux boot floppy to get its boot image from and it worked
    fine!

    > 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 ;)
    >
    > 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 ;)

    My shot in the dark would be to wonder if, to save space, this floppy
    uses an old/small version of mount that reports "no such device" where
    one would expect "mount point xxx does not exist", and there's no
    /floppy?

    > > 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.

    I'd have thought it'd be in the archives somewhere, but maybe you have
    to download the .iso and pull it out of that... I could always email
    you a copy. Would you object to receiving a 1.4 meg email?

    > > 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?

    The same (more or less) number of allocation units into the second
    partition. Not that it really matters, I think; it's a symptom of DOS
    misbehaving, not the drive, and the important consideration seems to
    be whether it happens rather than the precise details of how it
    happens, unless we intend to hack DOS to cure it :-)

    > > 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?

    That is my understanding, although I've never used it myself.
    Presumably under DOS you see something like pairs of files, possibly
    with odd names, with the data in one and the Linux attributes and long
    name etc. in the other.

    > 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.

    If that's all you're going to use it for, you might as well leave it
    as FAT. I don't see any reason why that would interfere with cdrecord,
    and if you're only ever going to have one large temporary file on
    there the limitations of FAT don't really matter. Plus you could use
    it for the same purpose in Windoze should the need arise.

    > 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.

    That's a BIOS limit to do with old BIOSes that don't do CHS
    translation [properly]. DOS's limits are at 2 gigs for a partition and
    8 gigs for a drive.

    > 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.

    Should go OK, I'd think... that worked OK for me.
     
    > > 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.

    Yeah. I remember bits of it that I've learnt by experience... I've had
    a Windoze system with a spare drive in it just to create/delete dummy
    partitions on so I can keep the important drive letters where I want
    them. 

    -- 
Pigeon
Be kind to pigeons
Get my GPG key here: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x21C61F7F



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