Richard Julian

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Quick and Dirty Guide to Command Line Wifi

09 Jun 2014

THE QUICK AND DIRTY

So, you’re working headless on the Raspberry Pi, Beaglebone Black, or just a machine which relies on wireless connection. Theoretically, you’re without an internet connection and therefore you don’t have access to easy tools like NetworkManager or wicd. As root/sudo, this is what you do:

**THE SETUP
**

In order to connect, one needs the very common wpasupplicant package installed. In many distros, this is installed by default.

Next up, it’s important to know your interfaces. Use ifconfig -a to list all interfaces (and identify your wireless interface name). Often, it is wlan0 or wlo0. Make sure the interface is up by running **ifconfig wlan0 up **(replace wlan0 with your wireless interface name).

Now, let’s create a config file to be used by wpa_supplicant. There’s a nifty command for generating this in the form of **wpa_passphrase [SSID] [password] > /etc/wpa.conf **where ssid is the name of the network, note: don’t enclose them in quotation marks.

**CONNECTING **

Now the fun part. Using the recently created config file, we’re going to connect to the network and then request an IP address from DHCP.

The command to connect is: wpa_supplicant -iwlan0 -Dwext -c/etc/wpa.conf . Once it authenticates successfully, in a different terminal, we request a new IP address by first releasing previous leases and then asking for a new lease: dhclient -r && dhclient wlan0

Granted you tailor this to your own interfaces and your device has correct drivers, you should be connected to the network. You can check by running ifconfig and seeing if the wireless interface has an IP address.

EXTRA HELP

So, that’s a very simple example. What if you don’t know the network ssid? Use wpa_cli to scan for network info (read the manpage). Instead of using the wext driver (which is a generic driver provided by wpa_supplicant), you could select a driver more suited to your wireless card. Troubleshoot effectively by checking the logs. In Debian-based distros, the log for wifi is often /var/log/daemon.log. Don’t want to waste an entire terminal on running wpa_supplicant? In addition to the many options, also give it -B so that it runs in the background.

And remember, search engines are your friends for troubleshooting wireless problems.