[olug] multiple OS's On 2 disks

Nathan Brown tbrownarcher at home.com
Wed Nov 29 17:03:27 UTC 2000


Will I be confined to using boot sectors below 1024?

Nate



 Brutsche wrote:

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> A long time ago, in a galaxy far, far way, someone said...
>
> > it just occurred to me that if you're booted into suse, you probably
> > won't have the redhat root mounted anywhere if your fs, and vice versa.
> > this would prevent lilo from being able to install both kernels and make
> > them available for booting.
> >
> > you may need to temporarily mount the the other distro's root directory,
> > then edit lilo.conf appropriately before running lilo
>
> Another way to do this would be to take advantage of the fact that PCs
> have 2 stages (or three, depending on OS and who you ask :)
>
> Stage 1: sector 0 of the hard disk; the MBR.  Usually, this stage will
>    load and run the first sector of the partition that's marked as
>    "bootable" - stage 2.
> Stage 2: This boot loader knows where the kernel for whatever OS you run
>    is located on disk.
> Stage 3: sometimes the kernel itself; sometimes a command-line utility to
>    be able to choose which kernel to load (note grub or the FreeBSD boot
>    loader, for example)
>
> The boot load I would use is grub.  It's a really neat little ditty of a
> boot loader - the stage1 goes in the MBR, and can read the stage2 from
> almost any device on the system.  grub's stage2 can read the following
> filesystems *directly*:
>  * ext2
>  * fat16/fat32
>  * reiserfs
>  * minix
>
> It also implements a menu system, and command line, and a method of
> netbooting PCs with rarp, dhcp, or bootp, and tftp to load the kernel
> image.
>
> I'm assuming the following:
>  * Windows /dev/hda
>  * RedHat on /dev/hdb1
>  * SuSE on /dev/hdb2
>
> This is what I would do:
>
> 1) install a grub RPM on suse or redhat, it doesn't matter which
> 2) make a grub menu; put it in Windows as c:\grubmenu.  My menu:
>
> timeout 5
> default 0
>
> title   Windows 98
> root    (hd0,0)
> makeactive
> chainloader +1
>
> title   RedHat
> kernel  (hd1,0)/vmlinuz root=/dev/hdb1
>
> title   SuSE
> kernel  (hd1,1)/vmlinuz root=/dev/hdb2
>
> 3) copy the stage1 and stage2 files from the grub distribution and put
>    them under c:\
> 4) run "grub" and enter these commands; I assume that Windows is on
>    /dev/hda1:
>
>    root (hd0,0)
>    install /stage1 (hd0) /stage2 /grubmenu
>
> Need to upgrade your kernel?  Make it /vmlinuz on the right file system
> and reboot.  Need to tweak the menu?  Edit grubmenu and reboot.
>
> PS: *keep* *an* *emergency* *boot* *floppy* (or cd) *available* for each
> OS.  It's easy to screw this stuff up!
>
> - --
> - ----------------------------------------------------------------------
> Phil Brutsche                                   pbrutsch at creighton.edu
>
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