I formatted my external USB-drive with GParted to ext2 file system. After that the usb-drive is automounted with root-permission and now I only can write with sudo to the drive. Of course I can change the permissions manually (chmod), but the behavior I want is that by inserting the drive it gets automounted with permission 7 independent of which user is logged in, like an usual usb-drive does. I hope my question is clear enough, if not I'll can clarify, just ask. Thx in advance!!