Raspberry Pi to configure automatically as an Access Point OR WiFi client

Question

There are many guides for setting up a Raspberry Pi as an Access Point, and even some which allow switching between Access Point and WiFi client.

I wanted a setting which would work as a normal WiFi Client (using dhcpcd) when one of my networks is available and as an Access Point otherwise.

Answer 1

In case you want to save some hassle as mentioned by Milliways. I suggested a short way. Command for installing RaspAP:

wget -q https://git.io/voEUQ -O /tmp/raspap && bash /tmp/raspap

Default SSID - raspi-webgui
Default Wifi Password - ChangeMe

Default Login:
user - admin
passwd - secret

Reference: https://www.youtube.com/watch?v=RvOyafQeOoY&t=33s

Let us know if it works. :)

Answer 2

Update While the below did work with the onboard WiFi interfaces it is a kludge, so I can not recommend it as a reliable solution.

This answer is based on the Foundation tutorial Setting up a Routed Wireless Access Point

If no networks can be found (by dhcpcd) the "Fallback Profile" is used to set a Static IP Address (and disable WiFi gateway).

This enables the Pi to be accessed headlessly by WiFi - which is handy when travelling without keyboard, monitor etc, but allows full network functionality when a known network is available.

The steps below are a modified (and simplified) version of the tutorial. You are urged to read the full tutorial before proceeding.

Install Software ¹

sudo apt update
sudo apt install dnsmasq hostapd
sudo systemctl stop dnsmasq
sudo systemctl stop hostapd
sudo reboot

^{1. The hostapd .service file is now automatically masked every time the package is upgraded with no valid configuration. After configuring you should unmask with sudo systemctl unmask hostapd.service}

Configuring a static IP Fallback Profile

Add the following to the end of /etc/dhcpcd.conf (This step differs from the Foundation tutorial)

# It is possible to fall back to a static IP if DHCP fails:
# define static profile
profile static_wlan0
  static ip_address=10.1.4.1/24
  nogateway
fallback to static profile on wlan0
interface wlan0
  fallback static_wlan0

You can test this by restarting dhcpcd - to see the static fallback you need to rename the network in /etc/wpa_supplicant/wpa_supplicant.conf so it will not be found by dhcpcd

sudo systemctl restart dhcpcd

Configuring the DHCP server (dnsmasq)

Type or copy the following information into the /etc/dnsmasq.conf configuration file and save it: NOTE the dhcp-range should match the static IP set in /etc/dhcpcd.conf

interface=wlan0
dhcp-range=10.1.4.2,10.1.4.20,255.255.255.0,24h

Configuring the Access Point host software (hostapd)

Save the following in /etc/hostapd/hostapd.conf

interface=wlan0
driver=nl80211
ssid=NameOfNetwork
hw_mode=g
channel=7
wmm_enabled=0
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=AardvarkBadgerHedgehog
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP

Edit /etc/default/hostapd and replace the line with #DAEMON_CONF with this:

DAEMON_CONF="/etc/hostapd/hostapd.conf"

Start it up

sudo systemctl start hostapd
sudo systemctl start dnsmasq

The latest update to Raspbian (2019-03-09) has changed hostapd "wpa (2:2.6-10)". You should run sudo systemctl unmask hostapd and sudo systemctl enable hostapd to ensure it runs on boot.

#Add routing and masquerade The Foundation tutorial includes instructions to add routing and masquerade. This is not necessary for my use case (and if I wanted to do this would probably write a systemd service, rather than the clumsy rc.local approach)

Strictly, when running as a WiFi client hostapd and dnsmasq are not needed, but seem to do no harm.

NOTE there are other tutorials which do a similar job. http://www.raspberryconnect.com/network has a number of different options and can automatically switch between Access Point and WiFi client, but is more complex and uses wpa_cli to switch between networks. This contains lots of helpful information.