Configuring Wi-Fi

The Raspberry Pi Wi-Fi adapter has two main operating modes:

  1. Client mode – RPi connects to an existing Wi-Fi network.
  2. Access point mode – RPi creates a Wi-Fi network that you can connect to.

On our RPi image the Wi-Fi adapter is configured to use the access point mode by default.

Changing the password or SSID (of the network name)

  1. Edit the /etc/wpa_supplicant/wpa_supplicant.conf file (using SSH connection):

     sudo nano /etc/wpa_supplicant/wpa_supplicant.conf
    

    In order to change the name of the Wi-Fi network, change the value of the ssid parameter; to change the password, change the psk parameter. For example:

     network={
         ssid="my-super-ssid"
         psk="cleverwifi123"
         mode=2
         proto=RSN
         key_mgmt=WPA-PSK
         pairwise=CCMP
         group=CCMP
         auth_alg=OPEN
     }
    
  2. Restart Raspberry Pi.

The Wi-Fi network password should be at least 8 characters.

If your wpa_supplicant.conf is not valid, Raspberry Pi will not allow Wi-Fi connections!

Switching adapter to the client mode

  1. Disable the dnsmasq service.

     sudo systemctl stop dnsmasq
     sudo systemctl disable dnsmasq
    
  2. Enable DHCP client on the wireless interface to obtain IP address. In order to do this, remove the following lines from the etc/dhcpcd.conf file:

     interface wlan0
     static ip_address=192.168.11.1/24
    
  3. Configure wpa_supplicant to connect to an existing access point. Change your /etc/wpa_supplicant/wpa_supplicant.conf to contain the following:

     ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
     update_config=1
     country=GB
    
     network={
         ssid="SSID"
         psk="password"
     }
    

    where SSID is the name of the network, and password is its password.

  4. Restart the dhcpcd service.

     sudo systemctl restart dhcpcd
    

Switching the adapter to the access point mode

  1. Enable the static IP address in the wireless interface. Add the following lines to your /etc/dhcpcd.conf file:

     interface wlan0
     static ip_address=192.168.11.1/24
    
  2. Configure wpa_supplicant to work in the access point mode. Change your /etc/wpa_supplicant/wpa_supplicant.conf file to contain the following:

     ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
     update_config=1
     country=GB
    
     network={
         ssid="CLEVER-1234"
         psk="cleverwifi"
         mode=2
         proto=RSN
         key_mgmt=WPA-PSK
         pairwise=CCMP
         group=CCMP
         auth_alg=OPEN
     }
    

    where CLEVER-1234 is the network name and cleverwifi is the password.

  3. Enable the dnsmasq service.

     sudo systemctl enable dnsmasq
     sudo systemctl start dnsmasq
    
  4. Restart the dhcpcd service.

     sudo systemctl restart dhcpcd
    

Below you can read more about how RPi networking is organized.

RPi network organization

Network operation in the image is supported by two pre-installed services:

  • networking — the service enables all network interfaces at startup [5].
  • dhcpcd — the service ensures that configuration of addressing and routing on the interfaces is obtained dynamically or specified statically in the config file.

To work in the router (access point) mode, RPi requires a DHCP server. It is used to automatically send the settings of the current network to connected clients. isc-dhcp-server or dnsmasq may be used for this.

dhcpcd

Starting with Raspbian Jessie, network settings are no longer defined in the /etc/network/interfaces file. Now dhcpcd is used for sending addressing and routing settings[4].

By default, a dhcp client is enabled in all interfaces. Settings for network interfaces are changed in the /etc/dhcpcd.conf file. An access point should have a static IP address. To specify one, add the following lines to the end of the file:

interface wlan0
static ip_address=192.168.11.1/24

If the interface is wireless (wlan), the dhcpcd service triggers wpa_supplicant [13], which in turn works directly with the Wi-Fi adapter, and sets it to the specified state.

wpa_supplicant

wpa_supplicant — the service configures the Wi-Fi adapter. The wpa_supplicant service does not run as a standalone service (although it exists as such), but is instead launched as a dhcpcd child process.

By default the config file is /etc/wpa_supplicant/wpa_supplicant.conf. An example of the configuration file:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1
country=GB

network={
        ssid=\"CLEVER-SMIRNOV\"
        psk=\"cleverwifi\"
        mode=2
        proto=RSN
        key_mgmt=WPA-PSK
        pairwise=CCMP
        group=CCMP
        auth_alg=OPEN
}

Inside the config file, general wpa_supplicant settings, and the settings for the adapter configuration are specified. The configuration file also contains network section with the basic settings of the Wi-Fi network, such as network SSID, password, adapter operating mode. There may be several network sections, but only the first valid one is used. For example, if the first section contains a connection to an unavailable network, the adapter will be configured according to a next valid section, if there is one. Read more about the syntax of wpa_supplicant.conf [TODO WIKI].

wpa_passphrase

wpa_passphrase — a utility for creating the network section.

wpa_passphrase SSID PASSWORD

After running the command, copy the resulting section to your config file. You may remove the commented field psk, and leave only the field with the password hash, or vice versa.

network={
    ssid="SSID"
    #psk="PASSWORD"
    psk=c2161655c6ba444d8df94cbbf4e9c5c4c61fc37702b9c66ed37aee1545a5a333
}

Multiple Wi-Fi adapters

The system may use multiple Wi-Fi adapters. If drivers are properly connected to them, they may be viewed by calling ifconfig (e.g. wlan0 and wlan1).

If you have multiple adapters, the same working network section will be used for all of them. This is due to the fact that for each interface, dhcpcd separately creates a child wpa_supplicant process, which runs the same code ( since the config is the same).

To make multiple adapters work with individual settings, the mechanism for running different configuration scripts is implemented in the called standard dhcpcd script. To use it, rename the standard config file as follows: wpa_supplicant-<interface name>.conf, for example wpa_supplicant-wlan0.conf.

To apply the settings, restart the parent process — the dhcpcd service. This can be done by running the following command:

sudo systemctl restart dhcpcd

DHCP server

dnsmasq-base

dnsmasq-base — a command-line utility, which is not a service. To use dnsmasq as a service, install the dnsmasq package.

sudo apt install dnsmasq-base
# Calling dnsmasq-base
sudo dnsmasq --interface=wlan0 --address=/clever/coex/192.168.11.1 --no-daemon --dhcp-range=192.168.11.100,192.168.11.200,12h --no-hosts --filterwin2k --bogus-priv --domain-needed --quiet-dhcp6 --log-queries

# More about dnsmasq-base
dnsmasq --help

# or
man dnsmasq

dnsmasq

sudo apt install dnsmasq
cat << EOF | sudo tee -a /etc/dnsmasq.conf
interface=wlan0
address=/clever/coex/192.168.11.1
dhcp-range=192.168.11.100,192.168.11.200,12h
no-hosts
filterwin2k
bogus-priv
domain-needed
quiet-dhcp6

EOF

isc-dhcp-server

sudo apt install isc-dhcp-server
# https://www.shellhacks.com/ru/sed-find-replace-string-in-file/
sed -i 's/INTERFACESv4=\"\"/INTERFACESv4=\"wlan0\"/' /etc/default/isc-dhcp-server
cat << EOF | sudo tee /etc/dhcp/dhcpd.conf
subnet 192.168.11.0 netmask 255.255.255.0 {
  range 192.168.11.11 192.168.11.254;
  #option domain-name-servers 8.8.8.8;
  #option domain-name "rpi.local";
  option routers 192.168.11.1;
  option broadcast-address 192.168.11.255;
  default-lease-time 600;
  max-lease-time 7200;
}

EOF
cat << EOF | sudo tee /etc/network/if-up.d/isc-dhcp-server && sudo chmod +x /etc/network/if-up.d/isc-dhcp-server
#!/bin/sh
if [ "\$IFACE" = "--all" ];
then sleep 10 && systemctl start isc-dhcp-server.service &
fi

EOF
  1. habr.com Linux WiFi from the command line with wpa_supplicant
  2. wiki.archlinux.org WPA supplicant (Russian)
  3. blog.hoxnox.com: WiFi access point with wpa_supplicant
  4. dmitrysnotes.ru: Raspberry Pi 3. Assigning a static IP addresses
  5. thegeekdiary.com: Linux OS Service ‘network’
  6. frillip.com: Using your new Raspberry Pi 3 as a Wi-Fi access point with hostapt (it also contains instructions for setting up forwarding for using RPi as an Internet gateway)
  7. habr.com: Configuring a ddns server on a GNU/Linux Debian 6 (Good article on configuring a ddns server based on bind and isc-dhcp-server)
  8. pro-gram.ru to: Setting up and configuring a DHCP server in Ubuntu 16.04. (setup isc-dhcp-server)
  9. expert-orda.ru: Configuring a DHCP server in Ubuntu (setup isc-dhcp-server)
  10. academicfox.com: A Raspberry Pi wireless access point (WiFi access point) (setting the routes, hostapd, isc-dhcp-server)
  11. weworkweplay.com: Automatically connect a Raspberry Pi to a Wifi network (Contains settings for creating an open access point)
  12. wiki.archlinux.org: WPA supplicant
  13. wiki.archlinux.org: dhcpcd (dhcpcd hook wpa_supplicant)

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