remote control of dual boot

Paul Howarth paul at city-fan.org
Thu Nov 18 13:31:28 UTC 2004


Jacques Dimanche wrote:
> Stewart Nelson wrote:
> 
>> I have a conventional dual-boot system:
>> Win XP on IDE primary master, grub in MBR,
>> FC2 on primary slave.
>>
>> If either Windows or FC2 is running, I can
>> access it with VNC.  Of course, a reboot will
>> switch to the default OS, if the other is running.
>> However, I don't know how to switch back.
>>
>> Is there a good way to boot FC2 from Windows?
>> Or to boot Windows from FC2?
> 
> Here is how I would do it.  I would make my linux be the default OS to 
> boot into.  You mentioned that you can control both OS'es remotely so 
> this shouldn't be a problem.  If you are in windows, then you can just 
> reboot to boot into linux.  While in linux, you can reboot into windows 
> by executing the following commands:
> 
> enter grub with:
>    grub --no-floppy (don't probe floppy drives makes it go faster if you 
> do not have a drive like all my machines)
> in the grub command line:
>    savedefault --default=2 --once    (replace 2 with the appropriate 
> selection that is your windows option in grub.conf)
>    quit
> Then you can reboot and it will boot into Windows.  When you reboot 
> again, it will go back into Linux.

The way I do it is to have the XP bootloader in the MBR, and have it 
chain-load grub to boot Linux. The first partition on the first disk is a 
small FAT partition that contains XP's boot.ini file. By manipulating this 
file (which, since it's on a filesystem that can be both read and written from 
both XP and Linux, can be done from either OS), I can choose which OS to boot 
by default and hence, what will get booted if I just reboot.

The key to this is having a bootloader configuration file on a filesystem that 
can be written by all OSes in use. In my case I'm OK because I have a FAT 
partition at the start of the disk, because I partitioned the disk with this 
in mind. An alternative approach might be to use ext2fsd 
(http://ext2fsd.sourceforge.net/), an ext2 filesystem driver for Windows, 
which could allow you to modify grub.conf from Windows.

Paul.




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