remote control of dual boot

Paul Howarth paul at
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 
(, an ext2 filesystem driver for Windows, 
which could allow you to modify grub.conf from Windows.


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