Hi thanks a lot for your answer (sorry to answer so late I thought I’de receive a mail as notification of answer…guess I forgot to tick the notification box…)
I’m must admit I’m quite a noob with programmation.
I found somewhere that I’d have to allow writing on the Usb drive using :
sudo chown -R pi:pi /media/usb/
Then I’d be able to do the chmod trick :
sudo chmod 777 /media/usb0
Does this seems correct to you?