Tuesday, February 19, 2013

Connecting wireless through command line

The first command you need to use is ifconfig. With this command you are going to enable your wireless device. Most likely your device will be called wlan0. So in order to enable this you would enter the command (as root):

ifconfig wlan0 up

You won’t see any feedback unless there is a problem.

The next step is to scan for your wireless network to make sure it is available. Do this with the following command:

iwlist wlan0 scan

With this command you will see output like the following:

Cell 01 - Address: 00:21:43:4E:9B:F0
Frequency:2.432 GHz (Channel 5)
Quality=100/100? Signal level:-45 dBm? Noise level=-95 dBm
Encryption key:on
IE: WPA Version 1
Group Cipher : TKIP
Pairwise Ciphers (1) : TKIP
Authentication Suites (1) : PSK
IE: IEEE 802.11i/WPA2 Version 1
Group Cipher : TKIP
Pairwise Ciphers (1) : CCMP
Authentication Suites (1) : PSK
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 22 Mb/s
6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s
36 Mb/s; 48 Mb/s; 54 Mb/s

So you know this network is available. From the above output you can also see this network is employing WPA2, so you will need a passkey. If you don’t know that passkey, you are out of luck (which would be the case no matter if you were using a front end in Linux, Windows, or Mac.)

Now it’s time to configure your connection. To do this issue the command:

iwconfig wlan0 essid NETWORK_ID key WIRELESS_KEY

Where NETWORK_ID is the ESSID of the network with which you want to connect and WIRELESS_KEY is the security key needed to connect to the wireless access point.

Note: iwconfig defaults to using a HEX key. If you want to use an ascii key you will have to add the “s:” prefix to your key like so:

iwconfig wlan0 essid NETWORK_ID key s:WIRELESS_KEY

Now that you have your configuration set, it’s time to get an IP address with the help of dhclient. Issue the command:

dhclient wlan0

If no output is reported there are no errors. You should now be up and running.

Make it a script

Of course who wants to type out all of those commands. Instead of doing this you could create a script for this like so:

#! /bin/bash
ifconfig wlan0
iwconfig wlan0 essid NETWORK_ID key WIRELESS_KEY
dhclient wlan0

Where NETWORK_ID is the actually essid of the network and WIRELESS_KEY is the security key for that network. Save this script with the filename and then make this script executable with the command:

chmod u+x

You can make this a global command by placing this script in /usr/local/bin. You can now issue the command from anywhere in your directory structure and it will run, connecting you to the configured wireless access point.

sudo iwconfig wlan0 freq 2.422G

Or by running:
sudo iwconfig wlan0 channel 3

ifconfig wlan0 down
iwconfig wlan0 mode managed
ifconfig wlan0 up
iwconfig wlan0 channel 3
iwconfig wlan0 key xxxxxxxxxx
iwconfig wlan0 key restricted
iwconfig wlan0 essid "Blah Blah Foo Bar"
iwconfig wlan0 ap xx:yy:zz:aa:bb:cc
sleep 5
dhcpcd -d wlan0

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