RPi as access point

How to setup a Raspberry Pi as an access point?

sudo apt install dnsmasq hostapd

Edit /etc/dhcpcd.conf

sudo nano /etc/dhcpcd.conf

Add to the end of the file

interface wlan0
    static ip_address=192.168.4.1/24
    nohook wpa_supplicant

restart dhcpcd

sudo systemctl restart dhcpcd

Configuring the DHCP server

sudo mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig
sudo nano /etc/dnsmasq.conf

Add the following

interface=wlan0      # Use the require wireless interface - usually wlan0
dhcp-range=192.168.4.2,192.168.4.200,255.255.255.0,24h

Reload dnsmasq

sudo systemctl reload dnsmasq

Configuring the access point host software (hostapd)

sudo nano /etc/hostapd/hostapd.conf

Add the following

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

Make sure config gets loaded

sudo nano /etc/default/hostapd

Uncommend and update DAEMON_CONF

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

Now enable and start hostapd

sudo systemctl unmask hostapd
sudo systemctl enable hostapd
sudo systemctl start hostapd

Edit /etc/sysctl.conf

sudo nano /etc/sysctl.conf

and uncomment this line:

net.ipv4.ip_forward=1

Reboot once

sudo reboot

Add a masquerade for outbound traffic on eth0:

sudo iptables -t nat -A  POSTROUTING -o eth0 -j MASQUERADE

Save the iptables rule.

sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"

Edit /etc/rc.local

sudo nano /etc/rc.local

and add this just above "exit 0" to install these rules on boot.

iptables-restore < /etc/iptables.ipv4.nat

Source: https://www.raspberrypi.org/documentation/configuration/wireless/access-point.md