Raspberry Pi #

Add WiFi AP #

Based on a forum post by pugbot.

1. Update the system … duh'. #

apt update && apt upgrade -y

2. Install necessary software #

We need an access-point daemon and a DHCP service for connecting clients:

apt install -y hostapd dnsmasq

3. Create configuration files #

Do not attempt to edit and interface files as some older guides say. They are not used anymore since buster.

Configure a new static address in /etc/dhcpcd.conf and prevent wpa_supplicant from messing with the interface:

interface uap0
  static ip_address=10.56.0.1/24
  nohook wpa_supplicant

Maybe backup the installed /etc/dnsmasq.conf config for reference and then configure it as follows:

interface=lo,uap0
bind-interfaces
server=192.168.1.1   # upstream dns
#domain-needed       # reject short names?
#bogus-priv          # reject private address spaces?
dhcp-range=10.56.0.2,10.56.0.99,1h

Now configure the access-point network in /etc/hostapd/hostapd.conf. The channel should match the station network but I found that it is changed automatically anyway to follow the current station.

channel=6
ssid=<some-name>
wpa_passphrase=<8-to-64-chars>
interface=uap0
hw_mode=g
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP
driver=nl80211
#wmm_enabled=1
#ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]

Add the config in the service defaults in /etc/default/hostapd:

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

4. Startup script #

Until now the above configuration is not applied on boot. So you can write yourself a startup script to enable the access point (and add it to /etc/rc.local if you want).

#!/bin/bash
set -x

# redundant stops to make sure services are not running
systemctl stop hostapd.service
systemctl stop dnsmasq.service
systemctl stop dhcpcd.service

# recreate uap0 interface
iw dev uap0 del
iw dev wlan0 interface add uap0 type __ap

# modify iptables for routing of clients
sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -s 10.56.0.0/24 ! -d 10.56.0.0/24 -j MASQUERADE

# bring up uap0 interface .. uncomment line if using dhcpcd.conf doesn't work
#ifconfig uap0 10.56.0.1 netmask 255.255.255.0 broadcast 10.56.0.255
ifconfig uap0 up

# start hostapd
systemctl start hostapd.service
sleep 10

# start the rest
systemctl start dhcpcd.service
sleep 5
systemctl start dnsmasq.service