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Hi,

I am using Lubuntu 11.04 with qemu. My Os loads applications from a fat32 file system. I pass the physical drive as the disk to qemu i.e -hda /dev/sda and my os does the directory parsing, reading etc.. But every change I make to the file system from the host is not shown in my Os until next reboot. I think it maybe that qemu internally caches disk accesses. So do anyone know of a solution or argument that I can pass to qemu to disable the cache. "cache=none" does not seem to work. Qemu documentation says that qemu may still internally cache even if that argument is passed. Rebooting every time I edit the applications for my Os defeats one of the main advantage of a virtual machine.

It is possible that your changes to /dev/sda is not commited by the Linux itself.
Try sync

Sorry for not mentioning it. I do unmounting and then mounting again the partition after an edit in the host. I did check it with a bunch of other utilities just to ensure whether it is the Linux itself that is caching or the qemu. And I did try sync before posting the question. It seems qemu is the culprit.

Found it. You have to pass the below arguement to qemu to disable guest disk caching and actually make qemu
wait on the disk IO.
qemu -drive file=/dev/sda,index=0,cache=none
instead of -hda /dev/sda