用 ubuntu16
http://www.finnie.org/software/raspberrypi/ubuntu-rpi3/ubuntu-16.04-preinstalled-server-armhf+raspi3.img.xz
默认账号：
name “ubuntu”, password “ubuntu”
bcm2835-cpufreq: Freq 900000->700000 (min=700000 max=900000 target=700000 request=700000)
原文：https://www.cnblogs.com/bootoo/p/11617916.html