On the N9, is there a way to get the system (usb-moded ?) to export the partition read-only. I don't want to get my N9 filled with viruses and other crap (or risk accidental file-deletion or the like) when plugging it into foreign Windoze machines ...

In the old days, USB-sticks had a physical read-only switch to accomplish exactly this ...

I suspect usb-moded doesn't support this, but would there be other ways ? Any ideas ?

I do not think this is possible , as it is the other host that is mounting the disk.
And vfat does not support any security options. Maybe if you go reformat to ext, you may get it safe (only give access to specific user). But then Windoze will not mount at all.

So even I would like to have smth like this I wont see it. But would like
to stay corrected!

Actually, since posting (isn't that always how it goes), I've been thinking something like this might be involved:

Setting up a loop-device, as read-only, referring to the original partition, and then exporting the loop device.

It is true that the external machine (Windoze, typically) would not understand that the partition is read-only, but I'm more concerned with protecting my data (on the N9), than not confusing the external machine.

But where to put the script that calls losetup ? Somewhere in /etc/init ? I haven't yet had time to experiment with this. Is it even allowed (my N9 is not jailbroken/incepted in any way, and I'm conservative that way) to put ones own scripts in /etc/init ?

I understand your need/wish. And idea about loop device is a nice idea.
In my N900 I fiddled with that and some scripts (cannot remember atm, but a search will show you). And ke-recv process is involved. pali made some improvements to this to automatically detect other file systems than vfat.
--edit
remembered:
/usr/sbin/osso-usb-mass-storage-mode-enable.sh
see attached file for any hints ...
--

But for N9 I am clueless. You may have a hex look into /usr/sbin/usbmoded ...

--
oh and btw
Without open mode / inception you most probably will MALF your device tinkering with soem system files. Beware.

usb_moded does support that It uses /etc/modprobe.d/meego.conf for module loading parameters (standard linux module loading behaviour).

So find in there the options line for g_file_storage and add ro=1

After saving it, the next time you use mass-storage it should be read-only.

However I do not know how badly the security system will react to that so you better have open mode or use inception before doing it.

Hey Philippe,

big Thank You.
That works!

This is really "standard linux behaviour"? (seems I need to lear a lot more coming/staying from/on maemo)

So I tested to add ro=1 just behind g_file_storage,
and I needed to
killall usb_moded
and then after selecting mass storage mode my device was connected in read-only mode. Nice!

So only thing to do (as root):
to get write protection and
to get back write possibilty (at home or save PC).

Disclaimer:
I have tested with open mode (so no problem), but this meego.conf file is not in refhashlist and I have booted with stock kernel and it did not malf. So it will work. But I cannot take responsiblity.

Thank you all for helping ! Much appreciated.

my choose is creating another 8gb partition and use it as mass storage for usb-moded.

And my choice, of course is never exporting MyDocs at all

I do all my transfers in/out of device via sftp or rsync, usually over wlan but for smaller files (or not time critical) over 3g.

Great!

Well usb_moded uses modprobe internally and the newer versions maintained for mer/nemo switched to kmod (which did not exist at the time when usb_moded was implemented for the N9). But in either case that means that modules are loaded in the standard linux way, which means that module parameters, blacklists etc which are stored in /etc/modprobe.d are used. This way there is no need to recompile or change usb_moded to have it behave differently on the module level.

The source code is here btw : https://gitorious.org/meego-middleware/usb_moded (as Nokia was so kind to release it under LGPL for MeeGo)