Android adb devices ???????????? no permissions issue on Ubuntu

Note: Device is Yureka (cyanogenmod).Trying to

In attempt of listing attached device

# adb devices
List of devices attached
???????????? no permissions
emulator-5554 device

So, I found this solution (Video Location https://www.youtube.com/watch?v=w3hr6lxNJrQ)

Solution is
#sudo apt-get install android-tools-adb

#sudo apt-get install android-tools-fastboot

(Install these two packages in ubuntu)
#sudo adb kill-server

#sudo adb start-server

#sudo adb devices
List of devices attached
emulator-5554 device
aaaaaaaa offline

Offline.You will find in your mobile you needed to allow this connection. After doing so

#sudo adb devices

List of devices attached 

emulator-5554 device

aaaaaaaa device