树莓派3 B+ / ubuntu-18.04.2 设置 wifi

首先按照网上的教程，给microSD卡format， 然后把ubuntu镜像拷上去。

开机，初始化系统

然后连一根网线

然后：

For the image with apt installed

Step1:

sudo apt-get install wireless-tools

Step2:

sudo apt-get install wpasupplicant

Step3: add to /etc/network/interfaces :

auto wlan0 
iface wlan0 inet dhcp
wpa-ssid WIRELESSSSID 
wpa-psk WIRELESSPASSWORD

Step4: comment from /etc/network/interfaces the line:

#source /etc/network/interfaces.d/*.cfg

the commented interfaces.d/*.cfg file contains settings for the eth0.

I do not understand why but leaving this line active and adding the wlan0 config would crash the system at boot.

Step5: reboot

For the core image without apt installed:

Step1:

ifconfig wlan0 down
ifconfig wlan0 up

Step2: create wireless config file:

sudo vi /etc/network/interfaces.d/wlan0

Note: I tried without sudo but it would not let me save the changes

Step3: add the following content

auto wlan0 
iface wlan0 inet dhcp
wpa-ssid WIRELESSSSID 
wpa-psk WIRELESSPASSWORD

Step4: reboot

其实都不需要reboot， 只要重启网卡即可：

sudo systemctl restart networking
sudo ifdown wlan0
sudo ifup wlan0
wpa_cli status