While the Raspberry Pi 3 has got an internal Wi-Fi adapter, Raspberry Pi 1, 2 and Zero have not. How can I deal with this?
While the Raspberry Pi 3 has got an internal Wi-Fi adapter, Raspberry Pi 1, 2 and Zero have not, so you need to plug a 802.11 adapter in.
Supported adapters’ firmware can be added with the following command via SSH as the root user:
apt update; apt install -y linux-wlan-ng firmware-linux-free
dahdi-firmware-nonfree firmware-atheros firmware-bnx2 firmware-bnx2x
firmware-brcm80211 firmware-intelwimax firmware-ipw2x00 zd1211-firmware
firmware-ivtv firmware-iwlwifi firmware-libertas firmware-linux-nonfree
firmware-myricom firmware-netxen firmware-qlogic firmware-ralink
Do not install linux-wlan-ng on the Raspberry Pi 3, its firmwares conflict with the built-in 80211 module.