When i try to upload the sketch (blink) to arduino it says:
avrdude: Version 6.3, compiled on Dec 16 2016 at 13:32:25
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "/Applications/Arduino.app/Contents/Java/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/Users/andreamedola/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/cu.usbmodemFA131
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
I just try it on Linux (ubuntu 14 i think..) and it says the same
avrdude: Version 6.3, compiled on Dec 16 2016 at 07:33:21
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
Copyright (c) 2007-2014 Joerg Wunsch
System wide configuration file is "/home/andrea/Documenti/Arduino/arduino-1.8.1/hardware/tools/avr/etc/avrdude.conf"
User configuration file is "/root/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/ttyACM0
Using Programmer : arduino
Overriding Baud Rate : 115200
avrdude: stk500_recv(): programmer is not responding
avrdude: stk500_getsync() attempt 1 of 10: not in sync: resp=0x00
etc....
For some reason he's looking in root's home directory for a config file. If you're using the IDE as a normal user, he's not going to let you look in root's home.
I'm guessing you may have run the IDE as root, possibly the first time you ran it.