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So basically, I'd like to use iwconfig to connect to my wifi network when I'm not inside X. But I just don't see a way to do it in the man page. Any idea?

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5 Answers 5

up vote 25 down vote accepted

iw(list/config) can only handle WEP.

You need wpa-supplicant for this.

sudo apt-get install wpasupplicant

In /etc/wpa_supplicant.conf you put your ssid and password.

gksu gedit /etc/wpa_supplicant.conf 

Example:

network={
            ssid="ssid_name"
             psk="password"
}

Assuming your interface is wlan0 you can connect to it with...

wpa_supplicant -B -iwlan0 -c/etc/wpa_supplicant.conf -Dwext && dhclient wlan0
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well thats nice that iwlist/iwconfig can handle only WEP but in my case wpa_supplicant -B -iwlan0 -c/etc/wpa_supplicant.conf -Dwext && dhclient wlan0 did not connected to the wireless network, though by default NetworkManager connects me to the network I want to try the command line way is there some mistake I am doing? –  Registered User Oct 10 '13 at 22:58

This link shows it all and worked fine for me: http://linux.icydog.net/wpa.php

I'm copying the contents here, so we have it, in case that site goes offline.

Command line WPA

Sometimes you'll be at a command line with no access to GUI networking tools -- but your access point is secured with WPA. What do you do?

Assuming your wireless card actually works (i.e. iwconfig can see it and interact with it), using wpa_supplicant is actually pretty simple. Installing wpa_supplicant

Most distros nowadays have wpa_supplicant installed by default. If you have the commands wpa_passphrase and wpa_supplicant available, then you're good to go. Otherwise, you will need to install the package by doing something like (for Ubuntu):

$ sudo apt-get install wpasupplicant

Or (for Fedora):

# yum install wpa_supplicant

Or whatever the command is for your distro.

Generating the config file

Now that wpa_supplicant is installed, we will create its configuration file. Once you know the SSID and WPA passphrase, all you have to do is run:

$ wpa_passphrase myrouter mypassphrase > wpa.conf

Of course, replace "myrouter" with the SSID of your router, "mypassphrase" with your WPA passphrase, and "wpa.conf" with whatever file you want to store the configuration in. This filename does not have to follow a particular format or have a particular extension.

Alternatively, to avoid typing the passphrase on the command line (so it doesn't get saved in the shell's history), you can specify just the SSID on the command line. wpa_passphrase will wait for you to type in the passphrase followed by enter:

$ wpa_passphrase myrouter > wpa.conf
mypassphrase

You should end up with a file looking like this:

network={
    ssid="myrouter"
    #psk="mypassphrase"
    psk=8ada1f8dbea59704ac379538b4d9191f6a72390581b4cd7a72864cea685b1a7f
}

Getting connected

Now we will actually run wpa_supplicant to connect to the wireless network. First, if your router broadcasts its SSID (they all do by default), you probably want to make sure your wireless card can actually see it:

$ iwlist scan

You might have to run that as root to force a refresh.

Next, you will need to know three pieces of information:

  1. Which wpa_supplicant wireless drivers to use for your card. Running wpa_supplicant --help lists the different drivers it has (under "drivers:"). As of 0.5.8, the useful choices are: wext, hostap, madwifi, atmel, ndiswrapper, and ipw (ipw is for old kernels only; >=2.6.13 should use wext). If you don't see a specific match for your card, try wext, as that's kind of the catch-all.
  2. The network device of your card. This is usually eth1 or wlan0, but if you're unsure you can just run iwconfig. It will report "no wireless extensions" for non-wireless devices and will display some data for any wireless devices.
  3. The path to the configuration file that you created in the previous step.

Now that you have this data, run (as root):

# wpa_supplicant -D[driver] -i[device] -c[/path/to/config]

There are no spaces between the options and parameters. Don't include the brackets as I just added those for clarity. For example, for my laptop it looks like this:

# wpa_supplicant -Dwext -ieth1 -c/root/wpa.conf

You can also run it in the background by using the -B option so that it doesn't take up your console.

Now you're associated with the network.

Getting online

To actually get online, you'll have to get an IP somehow. Most people will just want to get a dynamic IP from a DHCP server, probably the one built into the router. (I'm not going to cover setting a static IP and routing table because that's a beast in itself.)

To get a DHCP lease, first release whatever leases you're still holding onto (as root):

# dhclient -r

Then ask for a new lease (of course replacing eth1 with the name of your network device, the same one as you used in the previous section):

# dhclient eth1

You now have an IP, in theory at least. Happy surfing!

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FYI for unexperienced people, most wireless card interface names will be wlan<number>, so for example the first wireless card in your configuration will be wlan0 instead of eth1 –  xorinzor Dec 24 '13 at 16:31
    
Thanks, the wpa_passphrase command helped. I tried the accepted answer but the file was wrong, wpa_passphrase helped with that and then I just passed the second command from the accepted answer(I already knew for sure that it is called wlan0)... –  Lilian A. Moraru May 15 at 20:52

First brig your card up if it's not runnig:

ifconfig wlan0 up

Set the parameters acording to your network

iwlist wlan0 scan
iwconfig wlan0 essid NETWORK_ID key WIRELESS_KEY
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3  
I believe that this is for WEP only. No WPA ;) –  Rinzwind May 17 '12 at 15:57
    
Rinzwind is right. This is for WEP. Sorry for te mistake. –  LnxSlck May 17 '12 at 15:59
1  
no problem. Leave it here and someone will someday benefit from your answer ;) –  Rinzwind May 17 '12 at 16:00
    
will this work even without a key like an open network? –  EvoandroidEvo Oct 26 '12 at 18:44
    
Of course, simply don't set a key –  LnxSlck Oct 27 '12 at 16:13

There's actually a way to do it using NetworkManager, if you have the checkbox package installed.

sudo /usr/share/checkbox/create_connection SSID --security=wpa -key=WPA-KEY

(Credit: bug 923836, which came up in my searches on the topic.)

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I had trouble using wpa_supplicant directly to get on a wireless network. My network ID and password generated errors when I used the wpa_supplicant.conf file on the wpa_supplicant command line, e.g., sudo wpa_supplicant -iwlan0 -c/etc/wpa_supplicant.conf -B. I was able to work around it with wpa_cli. The command sequence I had to use, since I am using a Windows driver with Linux ndiswrapper, is:

sudo modprobe ndiswrapper sudo iwconfig wlan0 essid "" mode managed sudo wpa_cli identity "" password ""

I had the network set up by adding it in the wireless section of networking in the GUI, so that I could click on the wired or wireless network icon and select the wireless provider (which was sometimes necessary to complete the login).

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