I'm missing something, how do I use the DirAsDsk option to write files to a directory.
The manual is not clear in this part.

$ openmsx -machine Philips_NMS_8250 -diska .

and then?

Btw. I'm using openMSX 0.5.1 Linux version.

Did you read this already?

http://openmsx.sourceforge.net/manual/user.html#dirasdisk

I hope turbor will give a more complete reply here

The current DirAsDisk doesn't write files to the host-OS directory, neither does it know how to handle subdirectories on the emulated MSX floppy.

Using "openmsx -machine Philips_NMS_8250 -diska ." all the files in the . directory will be placed in a virtual floppy. If you alter those files on the host-OS the changes are immediately visible in the MSX session. Files created when openMSx is running will not become visible.

But when creating new files in the emulated MSX, the DirAsDisk routines will place that data in a file named '.sector.cache', and will not create them as host-OS files!
If however you alter the originally imported files the files in your host-OS are altered also. You can not make them bigger however, otherwise only a part will show up in your original file and the new part will also end up in the '.sector.cache'

So to get those new/bigger files to your host-OS you still need to copy the files (in your MSX) to a regular dsk files and use some extra tools to get them out of the dsk image.

The good news here is, that the soon-to-be-released openMSX 0.5.2 (or get the CVS version now :-) will have a new command called 'diskmanipulator' that is intended to handle directory imports/export between your host-OS and all kind of MSX devices (including partitions on the emulated sunrise IDE-HD )
Diskmanipulator also can deal with subdirectories on an fat12 MSX-dos2 disk, and can be used to create new HD and floppy images.
See using-diskmanipulator.txt for more info.

I'm going to try the cvs version this week-end.
openMSX works like a charm on my older pc with Vector Linux 5.01 SOHO (700 mhz Athlon, 512 MB, 128 MB graphics),
keep up to good work!