This question already has an answer here:
Since upgrading from 12.04 to 14.04, whenever I connect my Android Galaxy SII to my laptop via USB to charge, I get a dialog box that says
Unable to mount SAMSUNG Android Unable to open MTP device '[usb:002,021]'
If I want to mount it, I select the mounting option on the phone as usual, and it mounts fine as a USB mass storage device. I don't know why Ubuntu is trying to mount the device before it switches to USB mass storage mode.
Is there a way to disable this automounting, or at least to disable the dialog boxes when it fails? (I still want other USB devices to be mounted when inserted, as usual.) In other words, I want the sane 12.04 behaviour back.