WPA supplicant

wpa_supplicant is a cross-platform WPA Supplicant with support for WEP, WPA and WPA2 (IEEE 802.11i / RSN (Robust Secure Network)). It is suitable for both desktop and laptop computers and even embedded systems.

wpa_supplicant is the IEEE 802.1X/WPA component that is used in the client stations. It implements key negotiation with a WPA Authenticator and it controls the roaming and IEEE 802.11 authentication/association of the wireless driver.

Installation

Install wpa_supplicant from the official repositories.

Optionally wpa_supplicant_gui can be installed which provides wpa_gui, a graphical frontend for wpa_supplicant using the qt4 toolkit.

Configuration

wpa_supplicant provides a reference configuration file located at /etc/wpa_supplicant/wpa_supplicant.conf which contains detailed documentation for all the available options and their utilisation.

In its simplest form, a configuration file requires only a network block. For example:

/etc/wpa_supplicant/foobar.conf

network={
    ssid="..."
}

This can easily be generated using the wpa_passphrase tool. For example:

$ wpa_passphrase essid passphrase

network={
    ssid="essid"
    #psk="passphrase"
    psk=f5d1c49e15e679bebe385c37648d4141bc5c9297796a8a185d7bc5ac62f954e3
}

Once you have a configuration file, you can run wpa_supplicant daemon and connect to the wireless network:

# wpa_supplicant -B -i interface -c configuration_file

Tip: Both wpa_supplicant and wpa_passphrase can be combined to associate with almost all WPA2 (Personal) networks:

# wpa_supplicant -B -i interface -c <(wpa_passphrase essid passphrase)

All that remains is to simply connect using a static IP or DHCP. For example:

# dhcpcd interface

Connecting with wpa_cli

To associate with a wireless access point using wpa_supplicant, use the included command line tool wpa_cli. In order to use wpa_cli a "control interface" must be specified for wpa_supplicant. Do this by creating a config file (e.g. /etc/wpa_supplicant/wpa_supplicant-interface.conf) containing ctrl_interface=/var/run/wpa_supplicant.

Replace all instances of interface with the wireless network interface you want to run wpa_supplicant on, which you can find using ip link.

To enable saving changes made using wpa_cli, append the line update_config=1 to the configuration file, then start wpa_supplicant with

# wpa_supplicant -B -i interface -c /etc/wpa_supplicant/wpa_supplicant-interface.conf

Invoke wpa_cli with no arguments to get an interactive prompt (>). The prompt has tab completion and descriptions of completed commands. The command scan initiates a scan; a notification is issued when the scan is complete. Then:

> scan_results
bssid / frequency / signal level / flags / ssid
00:00:00:00:00:00 2462 -49 [WPA2-PSK-CCMP][ESS] MYSSID
11:11:11:11:11:11 2437 -64 [WPA2-PSK-CCMP][ESS] ANOTHERSSID

To associate with MYSSID, tell wpa_supplicant about it. Each network is indexed numerically, so the first network will have index zero. The PSK can be provided without quotes as an alternative to providing the passphrase in this example:

> add_network
0
> set_network 0 ssid "MYSSID"
> set_network 0 psk "passphrase"
> enable_network 0
<2>CTRL-EVENT-CONNECTED - Connection to 00:00:00:00:00:00 completed (reauth) [id=0 id_str=]

To save this network in the configuration file:

> save_config
OK

Maintaining a custom configuration

As discussed above we can make use of wpa_passphrase to generate a basic configuration which we can augment with additional networks and options of our choosing. This may be necessary for more advanced networks employing extensive use of EAP.

Firstly we will use wpa_passphrase to create our basic configuration file.

# wpa_passphrase essid passphrase > /etc/wpa_supplicant/wpa_supplicant-interface.conf

Tip: Some unusually complex passphrases may require input from a file:

# wpa_passphrase essid < passphrase.txt > /etc/wpa_supplicant/wpa_supplicant-interface.conf

Next add a ctrl_interface so that we may control the wpa_supplicant daemon. We can allow wpa_cli to edit this configuration by setting update_config=1.

/etc/wpa_supplicant/wpa_supplicant-interface.conf

ctrl_interface=DIR=/run/wpa_supplicant GROUP=wheel # allow control for members in the 'wheel' group
update_config=1

network={
    ssid="foobarssid"
    psk=f5d1c49e15e679bebe385c37648d4141bc5c9297796a8a185d7bc5ac62f954e3
}

Multiple network blocks may be appended to this configuration.

To start your network simply run the following:

# ip link set interface up
# wpa_supplicant -B -D nl80211 -i interface -c /etc/wpa_supplicant/wpa_supplicant-interface.conf
# dhcpcd -A interface

Note: nl80211 is preferred over the deprecated wext driver. For a list of supported drivers see the output of wpa_supplicant -h.

For networks of varying complexity please study the examples provided in the default /etc/wpa_supplicant/wpa_supplicant.conf file.

Starting with systemd

In order to enable wireless at boot, enable wpa_supplicant on your particular wireless interface. To get connectivity with DHCP, enable dhcpcd.service as well. Finally, to handle possible ethernet connections, install ifplugd and enable it on your ethernet interface. For instance, the invocations might look like

# systemctl enable wpa_supplicant@wlp3s1
# systemctl enable dhcpcd
# systemctl enable ifplugd@enp5s2

WPA Supplicant handles roaming for all the SSIDs in its configuration file, and ifplugd will configure ethernet and bring down wireless when an ethernet cable is plugged into the machine. dhcpcd takes care of leasing an IP on all interfaces.

The [Install] section of systemd services in the current version of wpa_supplicant is incorrect (bug report). If your interface name is not wlan0, it will be necessary to copy the service file to /etc/systemd/system/ and replace the [Install] section with:

[Install]
WantedBy=multi-user.target

See systemd#Editing_provided_unit_files for help with the editing.

Note: If you choose to use the interface specific version of dhcpcd you might want to replace the -w flag with -b so that it doesn't wait until it's assigned an address before forking to the background.

See also

• Kernel.org wpa_supplicant documentation