How to make wpa_cli work in NixOS

Preface

More than once I’ve found myself stuck at a place without a network connection in need of scanning for nearby access points. However, wpa_cli does not work out of the box when you’ve only set up your known SSID’s and pre-shared keys using

networking.wireless = {
  enabled = true;
  networks."my-ssid".psk = "helloworld42";
};

Enabling the control interface

The following line tends to be put at the top of the wpa_supplicant configuration file:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=wheel

This makes the control interface accessible by the wheel group. The manpage for wpa_supplicant.conf(5) states

[ctrl_interface] allow frontend (e.g., wpa_cli) to be used by all users in ‘wheel’ group

I’ve always added this line when I configured my /etc/wpa_supplicant.conf by hand in other operating systems, but I guess I forgot why I did it.

In NixOS this line should be added using extraConfig:

networking.wireless.extraConfig = ''
  ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=wheel
'';

The resulting wpa_supplicant.conf will then look something (if not exactly) like this:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=wheel

network={
  ssid="my-ssid"


  psk=fec51ab9d2363e43a2f5e454aa3eab77da1aa3ae21ba71ee806e1e1f5d3cf7bd

}

References

• man 5 wpa_supplicant.conf
• clever at #nixos @ freenode.net