fastboot 卡在 waiting for device

$ fastboot flash boot boot.img
   < waiting for device >

看看devices

$ fastboot devices
   no permissions  fastboot

唔……

$ sudo chown root:root /bin/fastboot
$ sudo chmod +s /bin/fastboot
$ fastboot devices
   7D89BCD6        fastboot
$ fastboot flash boot boot.img
   target reported max download size of 465031168 bytes
   sending 'boot' (9409 KB)...
   OKAY [  0.665s]
   writing 'boot'...
   OKAY [  0.961s]
   finished. total time: 1.666s

好了