Connecting to WiFi on Ubuntu 20.04 Headless Server

If you are running headless ubuntu server you will not be connected to the wireless automatically. The instructions below have been tested on Ubuntu 20.04 (Falcon) Server but should work with Ubuntu 18.04 (Bionic) and 16.04 (Xenial).

We will be following these steps:

Installing tools and utilities
Finding the wireless interface name
Scanning for the wireless connections
Setting up WPA config file
Connecting to the wireless network
Obtain IP address
Setup auto connect on boot

Requirements

You will need following utilities to connect to WiFi:

wireless-tools: Set of utilities for interacting with wireless devices
wpa_supplicant: Required to connect using WPA/WPA2 authentication

Install the requirement using following commands:

sudo apt install wireless-tools wpa_supplicant

Setup

Run iwconfig to get the interface name for your wirless device.

iwconfig

This will give you output similar to following:

enp4s0    no wireless extensions.

wlp5s0    IEEE 802.11  ESSID:off/any  
          Mode:Managed  Access Point: Not-Associated   Tx-Power=0 dBm
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on

lo        no wireless extensions.

enp0s31f6  no wireless extensions.

Output shows us that the interface wlp5s0 supports wireless connectivity. Next step is to scan the network.

sudo iw <interface> scan

The output will be similar to following:

---- truncated ----
BSS ab:cd:ef:01:23:45(on wlp5s0) -- associated
        last seen: 12274.418s [boottime]
        TSF: 573122111163 usec (6d, 15:12:02)
        freq: 5200
        beacon interval: 100 TUs
        capability: ESS Privacy RadioMeasure (0x1011)
        signal: -36.00 dBm
        last seen: 1036 ms ago
        Information elements from Probe Response frame:
        SSID: Uchiha_5G
        Supported rates: 6.0* 9.0 12.0* 18.0 24.0* 36.0 48.0 54.0 
        RSN:     * Version: 1
                 * Group cipher: CCMP
                 * Pairwise ciphers: CCMP
                 * Authentication suites: PSK
                 * Capabilities: 16-PTKSA-RC 1-GTKSA-RC (0x000c)
        BSS Load:
                 * station count: 7
                 * channel utilisation: 52/255
                 * available admission capacity: 0 [*32us]
---- truncated ----

The wireless network name will be mentioned under SSID. The RSN section signifies that the authentication is using WPA/WPA2 and Authentication suites is PSK which means Pre-Shared Key (a password). Now we create a configuration file for password using following command. The command will wait for your password on the shell (Replace WIFI_PASSWORD with your own password):

wpa_passphrase Uchiha_5G | sudo tee /etc/wpa_supplicant.conf
WIFI_PASSWORD

Run following command to connect to the Wireless network.

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

This will attempt to connect to the network and report if it faces any problems. This might take around a minute. If you see CTRL-EVENT-CONNECTED - Connection to ab:cd:ef:01:23:45 completed then all is well. You can do CTRL-C to exit to terminal. To run the command in background supply -B flag:

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

Lets verify if we are actually connected:

iw <interface> link

It should show an output similar to following:

Connected to ab:cd:ef:01:23:45 (on wlp5s0)
  SSID: Uchiha_5G
  freq: 5200
  RX: 1427916 bytes (13735 packets)
  TX: 235064 bytes (1390 packets)
  signal: -41 dBm
  rx bitrate: 6.0 MBit/s
  tx bitrate: 866.7 MBit/s VHT-MCS 9 80MHz short GI VHT-NSS 2

  bss flags:    short-slot-time
  dtim period:  3
  beacon int:   100

If your output shows Not connected then you should check if wpa_supplicant command is running in background using ps aux | grep wpa. You can run the wpa_supplicant command without the -B flag to check what is going wrong.

We are now connected to WiFi but we also need to get an IP Address from router. To do this we use the dhclient utility.

sudo /sbin/dhclient <interface>

Once this is done we can check the status using ifconfig to see if we are connected and have an ip address assigned. You can also run a ping-test to check if you have internet.

Auto-connect on boot

To setup auto-connect on boot we use systemd to run the same commands in correct order. Create a file /etc/systemd/system/connect-wireless.service with following content in it:

[Unit]
Description=WPA supplicant for connecting to My WiFi
After=wpa_supplicant.service
Wants=network.target
IgnoreOnIsolate=true

[Service]
ExecStart=/sbin/wpa_supplicant -c /etc/wpa_supplicant.conf -i <interface>

[Install]
WantedBy=multi-user.target

Create a service file /etc/systemd/system/dhclient.service for getting IP address after wpa_supplicant. Notice the After directive in the [Unit] section. If you are using different service name you should update this directive with the correct name to your wpa_supplicant service.

[Unit]
Description= DHCP Client
Before=network.target
After=connect-wireless.service

[Service]
Type=forking
ExecStart=/sbin/dhclient wlp5s0 -v
ExecStop=/sbin/dhclient wlp5s0 -r

[Install]
WantedBy=multi-user.target

Now we enable the services:

sudo systemctl enable connect-wireless.service
sudo systemctl enable dhclient.service

You can reboot and test if your services are working and connecting to wireless correctly.

Connecting to WiFi on Ubuntu 20.04 Headless Server

Jul 28, 2020

Requirements

Setup

Auto-connect on boot