Have you ever went to a place without wifi, and your friends wouldn't give out hotspot? I have, and in this instructables, I'll show you step by step on how to turn your Raspberry Pi into a wifi hotspot. Even better, this project will cost you less than a 100 USD!

Supplies

BOM:

Raspberry Pi 3 (technically any model will work but I find this model more consistent): https://www.amazon.com/Raspberry-Pi-MS-004-00000024-Model-Board/dp/B01LPLPBS8

Wifi Stick (this is optional as the raspberry pi already has builtin wifi, but the signal will be better with a wifi stick): https://www.amazon.com/Adapter-1200Mbps-TECHKEY-Wireless-Network-300Mbps/dp/B07J65G9DD/ref=sr_1_3?keywords=wifi+stick&qid=1583146106&sr=8-3

You'll also need keyboard mouse, a screen/monitor, and a power source which I got from a powerbank, (assuming you already have those.)

Step 1: Install and Update Raspbian

Update Raspbian by typing these commands:

sudo apt-get update
sudo apt-get upgrade

If you get an upgrade, It’s a good idea to reboot with sudo reboot.

Step 2: Install Hostapd and Dnsmasq

These are the two programs we’re going to use to make your Raspberry Pi into a wireless access point. To get them, just type these lines into the terminal:

sudo apt-get install hostapd

sudo apt-get install dnsmasq

Both times, you’ll have to hit y to continue. hostapd is the package that lets us create a wireless hotspot using a Raspberry Pi, and dnsmasq is an easy-to-use DHCP and DNS server. We’re going to edit the programs’ configuration files in a moment, so let’s turn the programs off before we start tinkering:

sudo systemctl stop hostapd

sudo systemctl stop dnsmasq

Step 3: Configure a Static IP for the Wlan0 Interface

For our purposes here, I’m assuming that we’re using the standard home network IP addresses, like 192.168.###.###. Given that assumption, let’s assign the IP address 192.168.0.10 to the wlan0

interface by editing the dhcpcd configuration file. Start editing with this command:

sudo nano /etc/dhcpcd.conf

Now that you’re in the file, add the following lines at the end:

interface wlan0

static ip_address=192.168.0.10/24

denyinterfaces eth0

denyinterfaces wlan0

(The last two lines are needed in order to make our bridge work –- but more on that in Step 8.) After that, press Ctrl+X, then Y, then Enter to save the file and exit the editor.

Step 4: Configure the DHCP Server (dnsmasq)

We’re going to use dnsmasq as our DHCP server. The idea of a DHCP server is to

dynamically distribute network configuration parameters, such as IP addresses, for interfaces and services. dnsmasq’s default configuration file contains a lot of unnecessary information, so it’s easier for us to start from scratch. Let’s rename the default configuration file and write a new one:

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

sudo nano /etc/dnsmasq.conf

You’ll be editing a new file now, and with the old one renamed, this is the config file that dnsmasq will use. Type these lines into your new configuration file:

interface=wlan0

dhcp-range=192.168.0.11,192.168.0.30,255.255.255.0,24h

The lines we added mean that we’re going to provide IP addresses between 192.168.0.11 and 192.168.0.30 for the wlan0 interface.

Step 5:

Another config file! This time, we’re messing with the hostapd config file. Open ‘er up:

sudo nano /etc/hostapd/hostapd.conf

This should create a brand new file. Type in this:

interface=wlan0

bridge=br0

hw_mode=g

channel=7

wmm_enabled=0

macaddr_acl=0

auth_algs=1

ignore_broadcast_ssid=0

wpa=2

wpa_key_mgmt=WPA-PSK

wpa_pairwise=TKIP

rsn_pairwise=CCMP

ssid=NETWORK

wpa_passphrase=PASSWORD

Note that where I have “NETWORK” and “PASSWORD,” you should come up with your own names. This is how you’ll join the Pi’s network from other devices. We still have to show the system the location of the configuration file:

sudo nano /etc/default/hostapd

In this file, track down the line that says #DAEMON_CONF=”” – delete that # and put the path to our config file in the quotes, so that it looks like this: DAEMON_CONF="/etc/hostapd/hostapd.conf"The # keeps the line from being read as code, so you’re basically bringing this line to life here while giving it the right path to our config file.

Step 6: Set Up Traffic Forwarding

The idea here is that when you connect to your Pi, it will forward the traffic over your Ethernet cable. So we’re going to have wlan0 forward via Ethernet cable to your modem. This involves editing yet another config file:

sudo nano /etc/sysctl.conf

Now find this line: #net.ipv4.ip_forward=1…and delete the “#” – leaving the rest, so it just reads:

net.ipv4.ip_forward=1

Step 7: Adding a New Iptables Rule

Next, we’re going to add IP masquerading for outbound traffic on eth0 using iptables:

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

…and save the new iptables rule:

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

To load the rule on boot, we need to edit the file /etc/rc.local and add the following line just above the line exit 0:

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

Step 8: Enabling Internet Connection

Now the Raspberry Pi is acting as an access point to which other devices can connect. However, those devices can’t use the Pi to access the internet just yet. To make the possible, we need to build a bridge that will pass all traffic between the wlan0 and eth0 interfaces.

To build the bridge, let’s install one more package:

sudo apt-get install bridge-utils

We’re ready to add a new bridge (called br0):

sudo brctl addbr br0

Next, we’ll connect the eth0 interface to our bridge:

sudo brctl addif br0 eth0

Finally, let’s edit the interfaces file:

sudo nano /etc/network/interfaces

…and add the following lines at the end of the file:

auto br0

iface br0 inet manual

bridge_ports eth0 wlan0

Step 9: Reboot

Now that we’re ready, let’s reboot withsudo reboot.

Now your Pi should be working as a wireless access point. Try it out by hopping on another device and looking for the network name you used back in step 5.