RaspberryPi/Wifi

See the following repo, which has details of how to configure /etc/network/interfaces:

https://git.charlesreid1.com/rpi/pi-join-wifi

The basics:

Joining Unencrypted Wifi

This supposes you want to join a wifi network called MyWifiNetwork that is unencrypted. Add the following wireless network information to /etc/network/interfaces.d/widy.cfg, which is a config file specific to this wifi router that you can use to swap wifi network configurations in and out:

auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wireless-essid OpenWrt

Next, include this config file in your /etc/network/interfaces file by adding the last line shown to it:

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet dhcp

source /etc/network/interfaces.d/mywifi.cfg