There can be several connection modes for a device running Android™:

• Mass Storage (MSC) : your device is detected as an external hard drive et requires a manual confirmation. 
• Android Debug Bridge (ADB) : specific mode for application developers. 

It is recommended to use the ADB mode for a computer running Linux. To activate this mode on your device, go in  (or) Settings >  Options for developers and tick the box USB Debugging.