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For esoteric reasons I have a server which only has WiFi access to the network.

By copying the necessary dpkg files on a removable drive I've managed to install wpa_supplicant.

The thing that's bugging me is that on other distributions configuring it can be done by editing /etc/wpa_supplicant/wpa_supplicant.conf. But this doesn't work on Ubuntu because the systemd service file starts up wpa_supplicant without specifying a configuration file. There is no -c specified in its arguments.

Even the Ubuntu man page says the most common way to start it is by specifying a config file...

In most common cases, wpa_supplicant is started with:

         wpa_supplicant -B -c/etc/wpa_supplicant.conf -iwlan0

Because this is a server there is no GUI installed and I'm not using network manager (AFAIK)

I have of course confirmed that shutting down the systemd service and manually starting the Daemon from the command line will work. And I can of course modify the .service file. But this feels like the wrong solution.

Can anyone tell me how I am supposed to configure wpa_supplicant on Ubuntu server?

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Philip Couling
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  • Looks a bit difficult. Why do you not want to use NetworkManager with nmtui? – N0rbert May 21 '20 at 19:55
  • Honestly I've never knowingly used network manager on a server before and have always considered it a desktop thing. I've always just configured interfaces manually. Are you suggesting that wpa_supplicant has been setup to only communicate with network manager by default? – Philip Couling May 21 '20 at 20:32
  • If I understand this correctly - the wpa_supplicant is used on embedded devices with limited resources (like cheap routers with OpenWRT-based firmware), so installation of NetworkManager is not possible here. But in your case - the resources are not limited and you can simply install NetworkManager here, I think. – N0rbert May 21 '20 at 20:41

2 Answers2

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It is not necessary to manually configure wpa_supplicant.

Networking in recent Ubuntu server versions is managed by netplan. Check to see the name of your netplan file:

ls /etc/netplan

I will assume that the name of the file you found is 01-netcfg.yaml. Substitute your details here if not 01-netcfg.yaml.

We will amend the file to specify your details:

sudo nano /etc/netplan/01-netcfg.yaml

Change the file to read:

network:
  version: 2
  renderer: networkd
  wifis:
    wlx-----:
      dhcp4: yes
      dhcp6: yes
      access-points:
        "network_ssid_name":
          password: "**********"

Please substitute your wireless interface name here instead of wlx----. Please note that the access point name and password are enclosed in quotation marks ". Spacing, indentation, etc. are crucial, please proofread carefully twice.

Save (Ctrl+o followed by Enter) and exit (Ctrl+x) the text editor nano. Follow with:

sudo netplan generate
sudo netplan apply

If you instead prefer a static IP address for the server, you can find the template here:

cat /usr/share/doc/netplan/examples/wireless.yaml
chili555
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  • Ah. I knew I was missing something. Out of interest, do you know which version of Ubuntu server started using netplan by default? – Philip Couling May 21 '20 at 21:03
  • Just to be clear does netplan use wpa_supplicant or can I remove that now? – Philip Couling May 21 '20 at 21:06
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    Ubuntu 17.10 started using netplan and you should retain wpa_supplicant. – chili555 May 21 '20 at 21:37
  • @chili555 great! Where the official documentation for your method may be found? I can't find anything related on https://help.ubuntu.com/ . But the https://wiki.ubuntu.com/Netplan/Design seems to be correct place, but provides small amount of details. – N0rbert May 21 '20 at 21:50
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    Please check here: https://netplan.io/ You can find many templates in /usr/share/doc/netplan/examples/ – chili555 May 21 '20 at 22:12
  • even works on default ubuntu! – imbr Oct 01 '21 at 22:14
  • Extra note: wpa_supplicant is implicitly required, as confirmed in the comments. Without it installed, this solution and others "work", but no connection still. I was setting up a vanilla minimal 18.04 LTS on a machine without WPA device, and wpa_supplicant was not installed. For the solution here to actually work, installing it was necessary (e.g. sudo apt-get install wpa_supplicant). At this point Netplan and the backends do not seem to report the missing assumption. – Eric Platon Dec 10 '21 at 02:00
  • @EricPlaton Correct. By default, Ubuntu server edition does not include the required packages wpa_supplicant and wireless-tools. However, since the original question was concerned with configuring wpa_supplicant. I felt safe to assume that it was previously installed. – chili555 Dec 10 '21 at 02:31
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In Ubuntu 20.04, wpa_supplicant uses DBus & unix domain sockets (like a pipe) to configure the daemon. Notice the "-u" & "-O" options on the command line for wpa_supplicant. It is done this way by secure design & system efficiency as it does not allow the passwords for the network connections to be exposed to the users of the system. This also makes for a more efficient programmatic interface for Gnome to configure the network settings as the socket file maps the configuration indirectly to shared memory instead of writing to a text file for all of the other applications to parse (i.e. less delay while changing settings & better coordination among processes).

To solve the problem described, you have several approaches that can be taken. It is just a matter of how much administration you want to do for the settings. You could: create another configuration file for wpa_supplicant (i.e. direct approach); modify the Netplan/yaml file for the individual network settings (i.e. indirect approach); or you could write a script which leverages the DBus programming interface (i.e. maintainable approach, as it doesn't depend on the development of the other tools). The first two are trivial solutions, but you'll gain more mastery & possibly earn more money if you learn to implement the last suggestion. Good luck!

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