Using WPA_Supplicant to Connect to WPA2 Wi-fi from Terminal on Ubuntu 16.04 Server

In this tutorial, we are going to learn how to connect to Wi-fi network from the command line on Ubuntu 16.04 server and desktop using wpa_supplicant.

In a modern home wireless network, communications are protected with WPA-PSK (pre-shared key) as opposed to WPA-Enterprise, which is designed for enterprise networks. WPA-PSK is also known as WPA-Personal. wpa_supplicant is an implementation of the WPA supplicant component. A supplicant in wireless LAN is a client software installed on end-user’s computer that needs to be authenticated in order to join a network.

Now let’s see how to connect to WPA2 wireless network using wpa_supplicant.

Step 1: Enable wireless interface

First, make sure your wireless card is enabled. You can use rfkill.

sudo apt install rfkill

To check the status of wireless card, run

rfkill list

Sample output:

As you can see, my wireless card is blocked by software. To unblock it, use the following command:

rfkill unblock wifi

If you are using the desktop version of Ubuntu, then you also need to stop Network Manager with the following command, otherwise it will cause connection problem when using wpa_supplicant.

sudo systemctl stop NetworkManager

To disable NeworkManager start at boot time, run

sudo systemctl disable NetworkManager

Step 2: Find your wireless interface name and wireless network name

Run iwconfig to find the name of your wireless interface.

iwconfig

wlan0 is a common name, but my wireless interface is called wlp3s0. You can also see that it’s not associated with any access point right now.

Then find your wireless network name by scanning nearby networks with the command below. Replace wlp3s0 with your own interface name. ESSID means network name.

sudo iwlist wlp3s0 scan | grep ESSID

Step 3: Connect to Wi-fi network using wpa_supplicant

Now install wpa_supplicant on Ubuntu 16.04.

sudo apt install wpasupplicant

We need to create a file named wpa_supplicant.conf using the wpa_passphrase utility. wpa_supplicant.conf is the configuration file describing all networks that the user wants the computer to connect to. Run the following command to create this file. Replace ESSID and Wi-fi passphrase with your own.

wpa_passphrase Your-ESSID passphrase | sudo tee /etc/wpa_supplicant.conf

The output will be piped to tee which then write to /etc/wpa_supplicant.conf file.

Now use the following command to connect your wireless card to wireless access point.

sudo wpa_supplicant -c /etc/wpa_supplicant.conf -i wlp3s0

By default, wpa_supplicant runs in the foreground. If the connection is completed, then open up another terminal window and run

iwconfig

You can see that the wireless interface is now associated with an access point.

You can press CTRL+C to stop the current wpa_supplicant process and run it in the background by adding -B option.

sudo wpa_supplicant -B -c /etc/wpa_supplicant.conf -i wlp3s0

Although we’re authenticated and connected to wireless network, but we don’t have an IP address yet. To obtain a private IP address from DHCP server, use the following command:

sudo dhclient wlp3s0

Now your wireless interface has a private IP address, which can be shown with:

ifconfig wlp3s0

Now you can access the Internet. To release the private IP address, run

sudo dhclient wlp3s0 -r

Connecting to Hidden Wireless Network

If your wireless doesn’t broadcast SSID, then you need to add the following line in /etc/wpa_supplicant.conf file.

scan_ssid=1

Like below:

network=
 ssid="LinuxBabe.Com office network"
 #psk="12345qwert"
 psk=68add4c5fee7dc3d0dac810f89b805d6d147c01e281f07f475a3e0195
 scan_ssid=1

Auto Connect on Startup

To automatically connect to wireless network at boot time, edit the wpa_supplicant.service file.

sudo nano /lib/systemd/system/wpa_supplicant.service

Find the following line.

ExecStart=/sbin/wpa_supplicant -u -s -O /run/wpa_supplicant

Change it to the following. Obviously you need to change wlp3s0 if that isn’t your interface name.

ExecStart=/sbin/wpa_supplicant -u -s -c /etc/wpa_supplicant.conf -i wlp3s0

Save and close the file. Then enable wpa_supplicant service to start at boot time.

sudo systemclt enable wpa_supplicant.service

Also we need to add the following line in /etc/rc.local file to obtain a private IP address at boot time.

dhclient wlp3s0

This line should be put above exit 0 like below.

#!/bin/sh -e

.......

# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

dhclient wlp3s0
exit 0

That’s it!

I hope this tutorial helped you set up Ubuntu server 16.04 wifi from the command line. As always, if you found this post useful, then subscribe to our free newsletter. You can also follow us on Google+,  Twitter or like our Facebook page.

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Using WPA_Supplicant to Connect to WPA2 Wi-fi from Terminal on Ubuntu 16.04 Server 2017-03-23T01:53:00-07:00 Rating: 4.5 Posted By: HOW TO