configuring grub boot option from a second pc

[Fabian Sturm]

Dear Grub developers and users!

I am trying to create an unconventional grub setup and stumbled into
some problems.

First I should describe what I want to achieve since there might be a
completely different solution possible :-)

I have two PCs available a client and a master. On the client PC I want
to run automated tests under windows.
And in between each automated test I want to reset the client PC to a
fresh windows image.

Therefore I have created two Partitions on the client. One partition
boots windows and executes the tests and the other partition is
configured in a way that on boot it formats the first partition and
copies a new windows image onto it. Which partition I boot is controlled
by grub. So under manual control I can decide in the boot manager if I
want to do tests or rather reset the windows partition. To fully
automate this process I now configured grub to boot on the serial
console so that the master PC can send the appropriate commands of this
serial connection to decide which partition to boot.

The only thing I forgot is, my client PC does not have a serial port!!
So I am now stuck, as far as I could find out, grub can't boot on a
serial to USB converter. Or are there ways to make this happen?

Or do you have any other ideas how I could decide from the master PC
which partition to boot on the client PC?

Any help is greatly appreciated!

Sincerely Fabian