Setting up a Wifi Hotspot on Ubuntu

The first thing I wanted to do after installing Ubuntu 12.04 is setup a wifi hotspot. I have a Samsung Netbook N130. I use a usb-modem to connect to the internet. I have a single data contract with Vodacom and I want all my devices to use this data at the same time.

Gathering information:

Opening a terminal and typing the following command :
#lspci
Showed me that I have a :
 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express)
#lsmod
Shows that it uses the ath9k drivers (this information may help you to google for setup information specific to your machine.)
Also
#iwconfig
will give you the name of your wireless adapter name for example:
“wlan0 “or “wlan1” (note that the “0″ and “1″ are numbers not letters)

Installing Programs

I then installed 2 programs via apt. In a terminal enter the following command:
#sudo apt-get install dhcp3-server
#sudo apt-get install hostapd

Editing Configuration Files

In a terminal:
#sudo gedit
This will bring up the editor with root privileges so that you can edit system files. (WARNING – editing system files can damage your system. Please do not edit system files unless you have made a backup of them first)
Open / Create the following files editing:
1. /etc/hostapd/hostapd.conf
interface=wlan0
driver=nl80211
ssid=my_hotspot
channel=1
hw_mode=g
auth_algs=1
wpa=3
wpa_passphrase=1234567890
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP CCMP
rsn_pairwise=CCMP
Please note: the “ssid” in this case “my_hotspot” is the name of the network that will show up on the device or laptop that will connect to the hotspot. The passphrase is a password – you can change this to any other 10 digit number. The device / laptop that wants to connect will have to enter this password.
Save the file.
2. /etc/default/isc-dhcp-server
Edit the line that says
INTERFACES=”"
To
INTERFACES=”wlan0″
Or change the “wlan0″ to “wlan1″ or whatever the wireless adapter name you have (see above section on gathering information.)
3. /etc/dhcp/dhcpd.conf
Make sure the follow lines are Commented out ( put a hash “#”  sign at the beginning of the line ) the following lines:
# option definitions common to all supported networks…
#option domain-name “example.org”;
#option domain-name-servers ns1.example.org, ns2.example.org;
#default-lease-time 600;
#max-lease-time 7200;
Add the following lines to the file (copy and paste)
subnet 10.10.0.0 netmask 255.255.255.0 {
        range 10.10.0.2 10.10.0.16;
        option domain-name-servers 8.8.4.4, 208.67.222.222;
        option routers 10.10.0.1;
}
(Note: the only other line in this whole config file that is uncommented is :
ddns-update-style none;)
4. /etc/default/hostapd
Add the following lines to the bottom of the file. Make sure similar lines are commented.
RUN_DAEMON=”yes”
DAEMON_CONF=”/etc/hostapd/hostapd.conf”
DAEMON_OPTS=”-dd”
(Note: This file makes sure hostapd program starts on bootup with your edited configuration files loaded)
5. /etc/network/interfaces
This is how my interfaces file looks:
auto lo
iface lo inet loopback
auto wlan0
iface wlan0 inet static
 address 10.10.0.1
 netmask 255.255.255.0
(Note: Again you must change every “wlan0″ to the name of your adapter. This file may have more entries for other network adapters. Just make sure you edit the section of the wireless adapter you want to use. This file will automatically configure the wireless network adapter’s network address at bootup time.)
At this stage you can reboot. And hopefully any device / laptop should connect to your wifi hotspots network via the network manager applet. On these devices search for the network “my_hotspot” and type in the password.
At this stage however you cannot access the Internet. Which brings us to another important step:

Internet connection Sharing.

You will need to ask yourself the following information. How do I connect to the internet on my ubuntu computer / laptop? In my case I use a usb 3G modem. You need to know the name of the network adapter that you connect to the internet on. > This must be different from the network adapter you configured above. (ie wlan0)
Connect to the internet, and in a terminal type:
#ifconfig
On my netbook, one of the entries is for adapter “ppp0″ this is the network adapter for my usb modem and the connection to the internet. The following steps use “ppp0″ however you can swap it for your adapter name:
To share the internet connection we have to do a thing called “ip masquerading”.
First we have to allow ip forwarding:
#sudo gedit
edit /etc/sysctl.conf
Make sure the following line is uncommented and reads
net.ipv4.ip_forward=1
Save and close gedit. (reboot)
After reboot: Connect to the Internet and In a terminal type:
# sudo iptables -t nat -A POSTROUTING -s 10.10.0.0/16 -o ppp0 -j MASQUERADE
(Note the “ppp0″ adapter name in the above line. The 10.10.0.0 is the ip address of your network that you configured in steps 3 and 5 above. Your wifi hotspot will thus share the internet with up to 15 machines that are given the ip addresses 10.10.0.2 to 10.10.0.16)
All devices and laptops should now be able to browse the internet and download email. If this works we have to make this permanent:
#sudo gedit
edit /etc/rc.local
add this line just before “exit 0″
iptables -t nat -A POSTROUTING -s 10.10.0.0/16 -o ppp0 -j MASQUERADE
Reboot / Connect to the internet and Enjoy your wifi hotspot.

Acknowledgements

When configuring and setting up mine I used and adapted the following  Howto’s and forums:
http://exain.wordpress.com/2011/03/31/making-a-wifi-hotspot-access-point-using-linux-wifi-lan-cardusb-adapter/
http://ubuntuforums.org/showthread.php?p=11890695#post11890695
http://ubuntuforums.org/showthread.php?p=11890408#post11890408


Source: https://thenewbieblog.wordpress.com/2012/05/01/wifi-hotspot-setup-on-ubuntu