Make Your Raspberry Pi a Wireless Access Point

I moved into dorm this semester again. There is only one Ethernet hole for me. But I have plenty devices that need to access the Internet! So I combine Raspberry Pi and a Wi-Fi USB adapter to build a Wireless access point.


This tutorial is based on two hardware which are listed below:

  • Raspberry Pi model B
  • Edimax EW-7811Un Wi-Fi nano USB adapter

First you need to make sure the Raspberry Pi is running Raspbian. If not, download the zip file from the official website and unzip it:

unzip 2015-05-05-raspbian-wheezy.zip

Insert the SD card which will be inserted into the Raspberry Pi into your computer. Here, I use Macbook Air as example. Locate the SD card:

diskutil list

In my case, /dev/disk2 is the SD card. Then try to unmount the SD card (whole disk, not specific partition) and write the image which we just downloaded and unzipped into it:

$ diskutil unmountDisk /dev/disk2
# dd if=2015-05-05-raspbian-wheezy.img of=/dev/rdisk2 bs=1m

Now the SD card is ready. Insert the card into the Raspberry Pi. Make sure the Ethernet cable and Wi-Fi USB adapter is connected, too. It’s time to turn on the power of the Pi!

Configuring Network

There are two network interfaces need to be configured:

  • eth0
  • wlan0

The wired one, i.e. eth0, is already configured, so we only need to setup wlan0. This interface is acted as a default gateway of our wireless devices that will connect with later. The configuration file is /etc/network/interfaces:

iface wlan0 inet static

To prevent the network interface settings being overwritten by DHCP server, we need to wake up the interface manually by inserting one line in /etc/rc.local:

ifup wlan0
exit 0

Also, the Raspberry Pi is a router in our scenario. It must have the ability to forward packets, i.e. receive the packets which are not destined to itself and lookup the routing table then forward them. Add this line in /etc/sysctl.conf to enable this when every time the Pi boots up:


Now we make the Pi receive the packets, the next important thing is NAT. The NAT function is done by iptables:

# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
# iptables -A FORWARD -i eth0 -o wlan0 -m state --state RELATED,ESTABLISHED -j ACCEPT
# iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT

To enable NAT function when the Pi boots up every time, the rules of iptables need to be dumped to an file for later use:

# iptables-save > /etc/iptables.rules

Let iptables read the rules from the file we created above before the network interface starts up. Write a simple shell scirpt in /etc/network/if-pre-up.d/iptables:

/sbin/iptables-restore < /etc/iptables.rules && exit 0

And finally set the execution bit up for the script:

# chmod a+x /etc/network/if-pre-up.d/iptables


HostAPD is a user space daemon for access point and authentication servers. Install it from apt-get:

# apt-get install hostapd

But the apt hosted HostAPD is a little buggy. It is not compatible with the RTL8188CUS chipset. Luckily, thanks to the Edimax team, they provide a patched version of it on the Internet. Download the patched HostAPD here.

$ unzip 0001-RTL8188C_8192C_USB_linux_v4.0.2_9000.20130911.zip
$ cd RTL8188C_8192C_USB_linux_v4.0.2_9000.20130911/wpa_supplicant_hostapd/
$ tar -zxvf wpa_supplicant_hostapd-0.8_rtw_r7475.20130812.tar.gz
$ cd wpa_supplicant_hostapd-0.8_rtw_r7475.20130812/hostapd/
$ make
# make install

Replace the hostapd binary with the newly compiled one:

# mv /usr/sbin/hostapd /usr/sbin/hostapd.bak
# cp /usr/local/bin/hostapd /usr/sbin/hostapd.edimax
# ln -s /usr/sbin/hostapd.edimax /usr/sbin/hostapd

Configure the HostAPD by editing /etc/hostapd/hostapd.conf. Remember to replace the “ssid” and “wpa_passphrase” for your own needs:


To make the HostAPD start at system boot, edit /etc/default/hostapd:



Last part of the tutorial. The wireless devices will need IP addresses to be able to access the network. Then DHCP server comes!

# apt-get install dnsmasq

The DHCP server will start up when it is installed. You need to stop it to edit the configuration file:

# service dnsmasq stop
# mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig
# touch /etc/dnsmasq.conf

Basic configuration:


Annnnnnnnnnnnnnnnd we are all set! Try to start the DHCP server or reboot the Raspberry Pi.