ifconfig -a
or:
ip a
To identify the status execute:
sudo wpa_cli -i wlan0 status
This provides details including, frequency of WiFi, BSSID, SSID, encryption (for WPA2-PSK, should see pairwise_cipher and group_cipher are CCMP) MAC address and IP address.
There are several options for turning off WiFi, what works will be dependent on how the system is configured. Assuming the WiFi interface is wlan0, options are:
sudo ifdown wlan0
sudo ifconfig wlan0 down
sudo ip link set wlan0 down
or, using rfkill:
-
First list all devices using:
sudo rfkill listThis will yield output similar to:
0: phy0: Wireless LAN Soft blocked: no Hard blocked: no 1: hci0: Bluetooth Soft blocked: no Hard blocked: noIn order to block WiFi excecute the following:
sudo rfkill block 0
Again, there are multiple options:
sudo ifup wlan0
sudo ifconfig wlan0 up
sudo ip link set wlan0 up
Alternatively, assuming the number of the device has been ascertained using rfkill list (0 in the example below) execute:
sudo rfkill unblock 0
Assuming WiFi interface is wlan0:
iwconfig wlan0
iwconfig wlan0 | grep -i --color "Quality\|Signal"
The numbers reported for quality will be WiFi driver dependent.
The file /proc/net/wireless contains information about the WiFi signal. This can be viewed continually using a combination of the cat and watch commands.
watch -n 1 cat /proc/net/wireless
Alternatively, the ncurses-based monitoring application wavemon can be used. This will likely need installing, which in Debian based distributions can be achieved using:
sudo apt install wavemon
To use the application simply run:
wavemon
Some of the above information sourced from 8 Linux Commands: To Find Out Wireless Network Speed, Signal Strength And Other Information
It is possible to set a preferred WiFi band, ie 2.5 or 5 GHz. This may be desirable to avoid interference from other devices or to improve range/speed. Remember, 2.5 GHz has the better range and 5 GHz the better speed.
First check the network interface is capable of using both bands. There are at least two methods to determine this.
Method 1
Run:
sudo iwlist wlan0 scan | grep -i "Frequency\|Address\|ESSID"
THe output will be similar to:
Cell 01 - Address: ab:12:cd:34:ef:56
Frequency:2.412 GHz
ESSID:"DESIRED SSID"
Cell 02 - Address: gh:78:ij:90:kl:12
Frequency:5.70 GHz
ESSID:"DESIRED SSID"
.....
Method 2
Run:
iw list | grep -i "Frequencies\|MHz\|GHz"
In the output look for the section(s) entitles Frequencies, which will be similar to:
Frequencies:
* 5180 MHz [36] (22.0 dBm) (no IR)
* 5200 MHz [40] (22.0 dBm) (no IR)
* 5220 MHz [44] (22.0 dBm) (no IR)
* 5240 MHz [48] (22.0 dBm) (no IR)
.....
The frequencies are the centre of the band.
Both the SSID and BSSID are required, the BSSID is the MAC address for a particular band of the access point. To obtain this information, enter the wpa command line interface by running the following, where wlan0 is the name of the wireless network interface:
sudo wpa_cli -i wlan0
Once in the iteractive mode, indicated by:
Interactive mode
>
run the following two commands, letting the first command complete execution (indicated by a return of the > prompt) before running the second.
scan
scan_results
The output will be similar to:
bssid / frequency / signal level / flags / ssid
ab:12:cd:34:ef:56 2412 -79 [WPA2-PSK-CCMP][WPA2-PSK-CCMP][ESS] DESIRED SSID
gh:78:ij:90:kl:12 5700 -84 [WPA2-PSK-CCMP][WPA2-PSK-CCMP][ESS] DESIRED SSID
.....
This shows the desired SSID and the frequencies, 2.5 and 5 GHz, along with their respective BSSIDs.
Quit the interactive mode by entering q.
To modify the settings
Kill network-manager and wpa_supplicant:
sudo service network-manager stop && sudo killall wpa_supplicant
On the Raspberry Pi (August 2020) networking this can be achieved using:
sudo service networking stop && sudo killall wpa_supplicant
If /etc/wpa_supplicant.conf does not exist, create the file using:
sudo wpa_passphrase <SSID> > /etc/wpa_supplicant
<SSID> must be replaced with the SSID of the WiFi network. A blank prompt will be received awaiting the user to enter the password for the WiFi. Once this has been done edit the file using:
sudo nano /etc/wpa_supplicant.conf
Add the following to the file.
ctrl_interface=/var/run/wpa_supplicant
#settings for an AP using preshared keys, PSK
network={
ssid=ssid
scan_ssid=1
key_mgmt=WPA-PSK
#psk==Password
psk="Passkey generated by wpa_passphrase"
bssid=gh:78:ij:90:kl:12 #the important part
}
#settings for an open AP. if you use this then don't use the above settings
network={
ssid="DESIRED SSID"
key_mgmt=NONE
bssid=gh:78:ij:90:kl:12
}
ssid and psk will be those entered when using the wpa_passphrase command.
Delete the commented line containing the password, and ensure the bssid matches that of the access point and the desired band you wish to connect to, ie 2.5 or 5 GHz.
Now start the daemon in the background by running:
sudo wpa_supplicant -B -c /etc/wpa_supplicant/wpa_supplicant.conf -i wlan0
If this fails, debug problems by running:
sudo wpa_supplicant -c /etc/wpa_supplicant/wpa_supplicant.conf -i wlan0 -d
Unsure about the dhclient section (next two commands)
After authentication, tell dhclient to release the current lease ie IP address, it has from the server:
sudo dhclient -r
Request a dynamic IPv4 address (DHCP):
sudo dhclient wlan0
Finally, reconfigure the interface with:
wpa_cli -i wlan0 reconfigure
Verify whether WiFi has successfully connected and the correct band is being used by executing:
sudo wpa_cli -i wlan0 status
If the ip_address is not populated, the device has not connected to the network, check that thr password and ESSID are correct.
Sources of information: