# WPA supplicant

Related articles

- Network configuration
- Wireless network configuration
- WPA2 Enterprise

wpa_supplicant is a cross-platform supplicant with support for WEP, WPA and WPA2 (IEEE 802.11i / RSN (Robust Secure Network)). It is suitable for desktops, laptops and 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 the wpa_supplicant package.

Optionally also install wpa_supplicant_gui, which provides wpa_gui, a graphical front-end for wpa_supplicant.

## Overview

The first step to connect to an encrypted wireless network is having wpa_supplicant obtain authentication from a WPA authenticator. In order to do this, wpa_supplicant must be configured so that it will be able to submit the correct credentials to the authenticator.

Once the authentication is successful, it will be possible to connect to the network by normally obtaining an IP address by setting it manually with the iproute2 suite or using some networking program, like systemd-networkd or dhcpcd, to configure an interface to obtain an IP address automatically via DHCP. See also the wireless and wired network configuration articles for methods and examples.

## Connecting with wpa_cli

This connection method allows scanning for the available networks, making use of wpa_cli, a command line tool which can be used to interactively configure wpa_supplicant at runtime. See wpa_cli(8) for details.

In order to use wpa_cli, a control interface must be specified for wpa_supplicant, and it must be given the rights to update the configuration. Do this by creating a minimal configuration file:

    /etc/wpa_supplicant/example.conf

    ctrl_interface=/run/wpa_supplicant
    update_config=1

Now start wpa_supplicant with:

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

Tip: To discover your wireless network interface name, issue the `ip link` command.

At this point run:

    # wpa_cli

This will present an interactive prompt (`>`), which has tab completion and descriptions of completed commands.

Tip: The default location of the control socket is `/var/run/wpa_supplicant/`, custom path can be set manually with the `-p` option to match the wpa_supplicant configuration. It is also possible to specify the interface to be configured with the `-i` option, otherwise the first found wireless interface managed by wpa_supplicant will be used.

Use the `scan` and `scan_results` commands to see the available networks:

    > scan
    OK
    <3>CTRL-EVENT-SCAN-RESULTS
    > 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`, add the network, set the credentials and enable it:

    > 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=]

If the SSID does not have password authentication, you must explicitly configure the network as keyless by replacing the command `set_network 0 psk "passphrase"` with `set_network 0 key_mgmt NONE`.

Note:

- Each network is indexed numerically, so the first network will have index 0.
- The PSK is computed from the quoted "passphrase" string, as also shown by the wpa_passphrase command. Nonetheless, you can enter the PSK directly by passing it to `psk` without quotes.

Finally save this network in the configuration file:

    > save_config
    OK

Once association is complete, all that is left to do is obtain an IP address as indicated in the #Overview, for example:

    # dhcpcd interface

## Connecting with wpa_passphrase

This connection method allows quickly connecting to a network whose SSID is already known, making use of wpa_passphrase, a command line tool which generates the minimal configuration needed by wpa_supplicant. For example:

    $ wpa_passphrase MYSSID passphrase

    network={
        ssid="MYSSID"
        #psk="passphrase"
        psk=59e0d07fa4c7741797a4e394f38a5c321e3bed51d54ad5fcbd3f84bc7415d73d
    }

This means that wpa_supplicant can be associated with wpa_passphrase and simply started with:

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

Note: Because of the process substitution, you cannot run this command with sudo - you will need a root shell. Just pre-pending sudo will lead to the following error:

    Successfully initialized wpa_supplicant
    Failed to open config file '/dev/fd/63', error: No such file or directory
    Failed to read or parse configuration '/dev/fd/63'

See also Help:Reading#Regular user or root.
Tip:

- Use quotes, if the input contains spaces. For example: `"secret passphrase"`
- To discover your wireless network interface name, issue the `ip link` command.
- Some unusually complex passphrases may require input from a file, e.g. `wpa_passphrase MYSSID < passphrase.txt`, or here strings, e.g. `wpa_passphrase MYSSID <<< "passphrase"`.

Finally, you should obtain an IP address as indicated in the #Overview, for example:

    # dhcpcd interface

## Advanced usage

For networks of varying complexity, possibly employing extensive use of EAP, it will be useful to maintain a customised configuration file. For an overview of the configuration with examples, refer to wpa_supplicant.conf(5); for details on all the supported configuration parameters, refer to the example file `/etc/wpa_supplicant/wpa_supplicant.conf`.

### Configuration

As is clear after reading #Connecting with wpa_passphrase, a basic configuration file can be generated with:

    # wpa_passphrase MYSSID passphrase > /etc/wpa_supplicant/example.conf

This will only create a `network` section. A configuration file with some more common options may look like:

    /etc/wpa_supplicant/example.conf

    ctrl_interface=/var/run/wpa_supplicant
    ctrl_interface_group=wheel
    update_config=1
    fast_reauth=1
    ap_scan=1

    network={
        ssid="MYSSID"
        psk=59e0d07fa4c7741797a4e394f38a5c321e3bed51d54ad5fcbd3f84bc7415d73d
    }

The passphrase can alternatively be defined in clear text by enclosing it in quotes, if the resulting security problems are not of concern:

    network={
        ssid="MYSSID"
        psk="passphrase"
    }

If the network does not have a passphrase, e.g. a public Wi-Fi:

    network={
        ssid="MYSSID"
        key_mgmt=NONE
    }

Further `network` blocks may be added manually, or using wpa_cli as illustrated in #Connecting with wpa_cli. In order to use wpa_cli, a control interface must be set with the `ctrl_interface` option. Setting `ctrl_interface_group=wheel` allows users belonging to such group to execute wpa_cli. This setting can be used to enable users without root access (or equivalent via sudo etc) to connect to wireless networks. Also add `update_config=1` so that changes made with wpa_cli to `example.conf` can be saved. Note that any user that is a member of the `ctrl_interface_group` group will be able to make changes to the file if this is turned on.

`fast_reauth=1` and `ap_scan=1` are the wpa_supplicant options active globally at the time of writing. Whether you need them, or other global options too for that matter, depends on the type of network to connect to. If you need other global options, simply copy them over to the file from `/etc/wpa_supplicant/wpa_supplicant.conf`.

Alternatively, `wpa_cli set` can be used to see options' status or set new ones. Multiple network blocks may be appended to this configuration: the supplicant will handle association to and roaming between all of them. The strongest signal defined with a network block usually is connected to by default, one may define `priority=` to influence behaviour.

An advantage to be mentioned in using a customized configuration file at `/etc/wpa_supplicant/wpa_supplicant.conf` is that it is used by default by dhcpcd. If you do so, you might want to make a backup of the original and delete the extensive network block examples in it. Otherwise, do not be surprised if your device suddenly connects to networks defined in them. In any case, changes to new versions of the configuration file should of course be merged.

Tip: To configure a network block to a hidden wireless SSID, which by definition will not turn up in a regular scan, the option `scan_ssid=1` has to be defined in the network block.

### Connection

#### Manual

First start wpa_supplicant command, whose most commonly used arguments are:

- `-B` - Fork into background.
- `-c filename` - Path to configuration file.
- `-i interface` - Interface to listen on.
- `-D driver` - Optionally specify the driver to be used. For a list of supported drivers see the output of `wpa_supplicant -h`.
  - `nl80211` is the current standard, but not all wireless chip's modules support it.
  - `wext` is currently deprecated, but still widely supported.

See wpa_supplicant(8) for the full argument list. For example:

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

followed by a method to obtain an ip address manually as indicated in the #Overview, for example:

    # dhcpcd interface

Tip: dhcpcd has a hook that can lauch wpa_supplicant implicitly, see dhcpcd#10-wpa_supplicant.

#### At boot (systemd)

The wpa_supplicant package provides multiple systemd service files:

- `wpa_supplicant.service` - uses D-Bus, recommended for NetworkManager users.
- `wpa_supplicant@.service` - accepts the interface name as an argument and starts the wpa_supplicant daemon for this interface. It reads the configuration file in `/etc/wpa_supplicant/wpa_supplicant-interface.conf`.
- `wpa_supplicant-nl80211@.service` - also interface specific, but explicitly forces the `nl80211` driver (see below). The configuration file path is `/etc/wpa_supplicant/wpa_supplicant-nl80211-interface.conf`.
- `wpa_supplicant-wired@.service` - also interface specific, uses the `wired` driver. The configuration file path is `/etc/wpa_supplicant/wpa_supplicant-wired-interface.conf`.

To enable wireless at boot, enable an instance of one of the above services on a particular wireless interface. For example, enable the `wpa_supplicant@interface` systemd unit.

Now choose and enable an instance of a service to obtain an ip address for the particular interface as indicated in the #Overview. For example, enable the `dhcpcd@interface` systemd unit.

Tip: dhcpcd has a hook that can lauch wpa_supplicant implicitly, see dhcpcd#10-wpa_supplicant.

### wpa_cli action script

wpa_cli can run in daemon mode and execute a specified script based on events from wpa_supplicant. Two events are supported: `CONNECTED` and `DISCONNECTED`. Some environment variables are available to the script, see wpa_cli(8) for details.

The following example will use desktop notifications to notify the user about the events:

    #!/bin/bash

    case "$2" in
        CONNECTED)
            notify-send "WPA supplicant: connection established";
            ;;
        DISCONNECTED)
            notify-send "WPA supplicant: connection lost";
            ;;
    esac

Remember to make the script executable, then use the `-a` flag to pass the script path to wpa_cli:

    $ wpa_cli -a /path/to/script

## Troubleshooting

Warning: Make sure that you are not using the default configuration file at `/etc/wpa_supplicant/wpa_supplicant.conf`, which is filled with uncommented examples that will lead to lots of random errors in practice. This is a known packaging bug of the wpa_supplicant package: FS#40661.

### nl80211 driver not supported on some hardware

On some (especially old) hardware, wpa_supplicant may fail with the following error:

    Successfully initialized wpa_supplicant
    nl80211: Driver does not support authentication/association or connect commands
    wlan0: Failed to initialize driver interface

This indicates that the standard `nl80211` driver does not support the given hardware. The deprecated `wext` driver might still support the device:

    # wpa_supplicant -B -i wlan0 -D wext -c /etc/wpa_supplicant/example.conf

If the command works to connect, and the user wishes to use systemd to manage the wireless connection, it is necessary to edit the `wpa_supplicant@.service` unit provided by the package and modify the `ExecStart` line accordingly:

    /etc/systemd/system/wpa_supplicant@.service.d/wext.conf

    [Service]
    ExecStart=
    ExecStart=/usr/bin/wpa_supplicant -c/etc/wpa_supplicant/wpa_supplicant-%I.conf -i%I -Dnl80211,wext

Note: Multiple comma separated driver wrappers in option `-Dnl80211,wext` makes wpa_supplicant use the first driver wrapper that is able to initialize the interface (see wpa_supplicant(8)). This is useful when using mutiple or removable (e.g. USB) wireless devices which use different drivers.

### Problem with mounted network shares (cifs) and shutdown

When you use wireless to connect to network shares you might have the problem that the shutdown takes a very long time. That is because systemd runs against a 3 minute timeout. The reason is that WPA supplicant is shut down too early, i.e. before systemd tries to unmount the share(s). A bug report suggests a work-around by editing the `wpa_supplicant@.service` as follows:

    /etc/systemd/system/wpa_supplicant.service.d/override.conf

    [Unit]
    After=dbus.service

### Password-related problems

wpa_supplicant may not work properly if directly passed via stdin particularly long or complex passphrases which include special characters. This may lead to errors such as `failed 4-way WPA handshake, PSK may be wrong` when launching wpa_supplicant.

In order to solve this try using here strings `wpa_passphrase <MYSSID> <<< "<passphrase>"` or passing a file to the `-c` flag instead:

    $ wpa_supplicant -i <interface> -c /etc/wpa_supplicant/wpa_supplicant.conf

In some instances it was found that storing the passphrase cleartext in the `psk` key of the `wpa_supplicant.conf` `network` block gave positive results (see [1]). However, this approach is rather insecure. Using `wpa_cli` to create this file instead of manually writing it gives the best results most of the time and therefore is the recommended way to proceed.

## See also

- WPA Supplicant home
- wpa_cli usage examples
- wpa_supplicant(8)
- wpa_supplicant.conf(5)
- wpa_cli(8)
- Kernel.org wpa_supplicant documentation

Categories:

- Wireless networking
- Network configuration