adb devices ???????????? no permission
Solution:
在/etc/udev/rules.d/目录下创建51-android.rules文件，
sudo vi /etc/udev/rules.d/51-android.rules
只要在51-android.rules中保留一行
SUBSYSTEM=="usb", ENV{DEVTYPE}=="usb_device", MODE="0666"
就好了~
修改以后重新插入你的Android设备，运行adb devices命令看看：
yajun@yajun-ThinkPad-X220:~/Downloads$ adb devices
List of devices attached
???????????? no permissions
yajun@yajun-ThinkPad-X220:~/Downloads$ adb devices
List of devices attached
MT-HYOFKZ6SYHUCK77P device
