Connect to a WIFI network from Ubuntu Terminal

Requirements

- An Ubuntu PC and Internet connection (Ethernet).
+ Tested version: Ubuntu 14.04

- A WIFI network card.

- A WIFI Router that offers DHCP IP address.

Choose your network and carry on.

1. Open WIFI Network (No password):

Code:

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$ ifconfig wlan0 down
$ dhclient wlan0 -r
$ ifconfig wlan0 up
$ iwconfig wlan0 essid "your_essid"
$ iwconfig wlan0 mode Managed
$ dhclient wlan0

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2. WEP WIFI Network:

Code:

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$ ifconfig wlan0 down
$ dhclient wlan0 -r
$ ifconfig wlan0 up
$ iwconfig wlan0 essid "essid"
$ iwconfig wlan0 mode Managed
$ iwconfig wlan0 key hexadecimal_key
OR
$ iwconfig wlan0 key s:ascii_key
$ dhclient wlan0

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3. WPA/WPA2 WIFI Network:

This is a little bit different method. First, you have to install wpasupplicant package:

Code:

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$ sudo apt-get install wpasupplicant

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Next, create a file that we'll call "wireless-wpa.conf":

Code:

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$ sudo nano wireless-wpa.conf

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Now, write the following code inside:

Code:

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ctrl_interface=/var/run/wpa_supplicant
 
network={
          ssid="the_router_ssid"
          scan_ssid=1
          key_mgmt=WPA-PSK
          psk="the_wpa_key"
        }

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Save the file. Now execute the following:

Code:

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$ ifconfig wlan0 down
$ dhclient wlan0 -r
$ ifconfig wlan0 up
$ iwconfig wlan0 mode Managed
$ killall wpa_supplicant
$ wpa_supplicant -B -Dwext -i wlan0 -c ./wireless-wpa.conf -dd

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$ wpa_supplicant -B -Dwext -i wlan0 -c ./wireless-wpa.conf

-B means run wpa_supplicant in the background.
-D specifies the wireless driver. wext is the generic driver.
-c specifies the path for the configuration file.

Obtain IP address by DHCP

Code:

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$ sudo dhclient wlan0

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Use the ip command to verify the IP address assigned by DHCP.

Code:

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$ ip addr show wlan0

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that's all!!