Click for USB WiFi Adapter Information for Linux

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8821cu ( 8821cu.ko ) 🚀

Linux Driver for USB WiFi Adapters that are based on the RTL8811CU, RTL8821CU and RTL8731AU Chipsets

• v5.8.1.7 (Realtek) (2020-09-29)
• Plus updates from the Linux community

Features

• IEEE 802.11 b/g/n/ac WiFi compliant
• 802.1x, WEP, WPA TKIP and WPA2 AES/Mixed mode for PSK and TLS (Radius)
• IEEE 802.11b/g/n/ac Client mode
  • Support wireless security for WEP, WPA TKIP and WPA2 AES PSK
  • Support site survey scan and manual connect
  • Support power saving mode
• Supported interface modes:
  • IBSS
  • Managed
  • AP
  • Monitor
  • P2P-client
  • P2P-GO
• Log level control
• LED control
• Power saving control
• VHT control (allows 80 MHz channel width in AP mode)

A FAQ is available at the end of this document.

Compatible CPUs

• x86, amd64
• ARM, ARM64

Compatible Kernels

• Kernels: 2.6.24 - 5.8 (Realtek)
• Kernels: 5.9 - 5.15

Tested Linux Distributions

• Arch Linux (kernel 5.4)

• Arch Linux (kernel 5.9)

• Fedora (kernel 5.11)

• Linux Mint 20.2 (Linux Mint based on Ubuntu) (kernel 5.11)

• Linux Mint 20 (Linux Mint based on Ubuntu) (kernel 5.4)

• LMDE 4 (Linux Mint based on Debian) (kernel 4.19)

• Manjaro 20.1 (kernel 5.9)

• Raspberry Pi OS (2021-01-11) (ARM 32 bit) (kernel 5.10)

• Raspberry Pi Desktop (x86 32 bit) (kernel 4.19)

• Ubuntu 21.04 (kernel 5.11)

• Ubuntu 20.04 (kernel 5.4)

Download Locations for Tested Linux Distributions

• Arch Linux
• Fedora
• Linux Mint
• Manjaro
• Raspberry Pi OS
• Ubuntu

Tested Hardware

• EDUP EP-AC1651 USB WiFi Adapter AC650 Dual Band USB 2.0 Nano

• EDUP EP-AC1635 USB WiFi Adapter AC600 Dual Band USB 2.0

Compatible Devices

• Cudy WU700
• BrosTrend AC5L
• EDUP EP-AC1651
• EDUP EP-AC1635
• TOTOLINK A650UA v3
• Mercusys MU6H (multi-state)
• Numerous additional products that are based on the supported chipsets

Warning: Beware of "multi-state" USB WiFi adapters. Some USB WiFi adapters have proprietary Windows drivers onboard. When plugged in, they act like a flash drive or CDROM and on Windows will attempt to start installing the Windows driver. That won't work on Linux or MAC or any other non-Windows OS so the adapter sits there in flash drive or CDROM mode. The problem is that the state of the adapter has to be changed for the adapter to show up as the device that you expect, in this case, a WiFi adapter. Most modern Linux distributions ship with a utility called "usb-modeswitch" that will handle this issue for you if it has the correct information for your adapter. It is a good utility but if you buy adapters that are "multi-state," that is one more potential headache you may have to deal with when something goes wrong. Often you can indentify adapters that are "multi-state" as they are advertised as "free driver" or "free installation driver." If you are looking to buy a USB WiFi adapter for use on Linux, MAC OS, *NIX or anything besides Windows, it is a good idea to seek out single-state adapters.

Note: Some adapter makers change the chipsets in their products while keeping the same model number so please check to confirm that the product you plan to buy has the chipset you are expecting.

Installation Information

The installation instructions are for the novice user. Experienced users are welcome to alter the installation to meet their needs.

Temporary internet access is required for installation. There are numerous ways to enable temporary internet access depending on your hardware and situation. One method is to use tethering from a phone.. Another method to enable temporary internet access is to keep a wifi adapter that uses an in-kernel driver in your toolkit.

You will need to use the terminal interface. The quick way to open a terminal: Ctrl+Alt+T (hold down on the Ctrl and Alt keys then press the T key)

DKMS is used for the installation. DKMS is a system utility which will automatically recompile and install this driver when a new kernel is installed. DKMS is provided by and maintained by Dell.

It is recommended that you do not delete the driver directory after installation as the directory contains information and scripts that you may need in the future.

There is no need to disable Secure Mode to install this driver. If Secure Mode is properly setup on your system, this installation will support it.

Installation Steps

Step 1: Open a terminal (Ctrl+Alt+T)

Step 2: Update the system (select the option for the OS you are using)

    Option for Debian based distributions such as Ubuntu, Linux Mint, Kali and the Raspberry Pi OS

    $ sudo apt update

    Option for Arch based distributions such as Manjaro

    $ sudo pacman -Syu

    Option for Fedora based distributions

    # sudo dnf -y update

Step 3: Install the required packages (select the option for the OS you are using)

    Option for Raspberry Pi OS

    $ sudo apt install -y raspberrypi-kernel-headers bc build-essential dkms git

    Option for Debian, Kali or Linux Mint Debian Edition (LMDE)

    $ sudo apt install -y linux-headers-$(uname -r) build-essential dkms git libelf-dev

    Option for Ubuntu (all flavors) or Linux Mint

    $ sudo apt install -y dkms git

    Options for Arch or Manjaro

    1) if using pacman

    $ sudo pacman -S --noconfirm linux-headers dkms git

Note: If you are asked to choose a provider, make sure to choose the one that corresponds to your version of the linux kernel (for example, linux510-headers for Linux kernel version 5.10) if you install the incorrect version, you'll have to uninstall it and reinstall the correct version.

    2) if using an AUR helper like paru or yay

    $ paru -S rtl8814au-dkms-git

Note: Make sure to uninstall any existing driver installations from other installation method. If the installation fails and its cause is related to AUR's BUILDPKG script, please address the issue first to the package maintainer at https://aur.archlinux.org/packages/rtl8814au-dkms-git/.

    Option for Fedora

    # sudo dnf -y install git dkms kernel-devel kernel-debug-devel

Step 4: Create a directory to hold the downloaded driver

$ mkdir ~/src

Step 5: Move to the newly created directory

$ cd ~/src

Step 6: Download the driver

$ git clone https://github.com/morrownr/8821cu.git

Step 7: Move to the newly created driver directory

$ cd ~/src/8821cu

Step 8: Warning: this step only applies if you are installing to Raspberry Pi hardware.

Run a preparation script

    Option for 32 bit operating systems to be installed to Raspberry Pi hardware

    $ ./raspi32.sh

    Option for 64 bit operating systems to be installed to Raspberry Pi hardware

    $ ./raspi64.sh

Step 9: Run the installation script (For automated builds, use NoPrompt as an option)

$ sudo ./install-driver.sh [NoPrompt]

Step 10: Reboot

$ sudo reboot

Driver Options

A file called 8821cu.conf will be installed in /etc/modeprobe.d by default.

Location: /etc/modprobe.d/8821cu.conf

This file will be read and applied to the driver on each system boot.

To edit the driver options file, run the edit-options.sh script.

$ sudo ./edit-options.sh

Documentation for Driver Options is included in the file 8821cu.conf.

Removal of the Driver

Note: This script should be used in the following situations:

• the driver is no longer needed
• a fresh start with default settings is needed
• a new version of the driver needs to be installed
• a major operating system upgrade is going to be applied

Note: This script removes everything that has been installed, with the exception of the packages installed in Step 3 and the driver directory. The driver directory can and probably should be deleted in most cases after running the script.

Step 1: Open a terminal (Ctrl+Alt+T)

Step 2: Move to the driver directory

$ cd ~/src/8821cu

Step 3: Run the removal script

$ sudo ./remove-driver.sh

Step 4: Reboot

$ sudo reboot

Recommended WiFi Router/ Access Point Settings

Note: These are general recommendations, some of which may not apply to your specific situation.

Security: Set WPA2-AES. Do not set WPA2 mixed mode or WPA or TKIP.

Channel width for 2.4G: Set 20 MHz fixed width. Do not use 40 MHz or 20/40 automatic.

Channels for 2.4G: Set channel 1 or 6 or 11 depending on the congestion at your location. Do not set automatic channel selection.

Mode for 2.4G: For best performance, set "N only" if you no longer use B or G capable devices.

Network names: Do not set the 2.4G Network and the 5G Network to the same name. Note: Unfortunately many routers come with both networks set to the same name.

Channels for 5G: Not all devices are capable of using DFS channels. It may be necessary to set a fixed channel in the range of 36 to 48 or 149 to 161 in order for all of your devices to work on 5g. (for US, other countries may vary)

Best location for the wifi router/ access point: Near center of apartment or house, at least a couple of feet away from walls, in an elevated location.

Check congestion: There are apps available for smart phones that allow you to check the congestion levels on wifi channels. The apps generally go by the name of WiFi Analyzer or something similar.

After making and saving changes, reboot the router.

Set regulatory domain to correct setting in OS

Check the current setting

$ sudo iw reg get

If you get 00, that is the default and may not provide optimal performance.

Find the correct setting here: http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2

Set it temporarily

$ sudo iw reg set US

Note: Substitute your country code if you are not in the United States.

Set it permanently

$ sudo nano /etc/default/crda

Change the last line to read:

REGDOMAIN=US

Recommendations regarding USB

• Moving your USB WiFi adapter to a different USB port has been known to fix a variety of problems. Problems include WiFi going on and off as well as connections coming and going.

• If connecting your USB WiFi adapter to a desktop computer, use the USB ports on the rear of the computer. Why? The ports on the rear are directly connected to the motherboard which will reduce problems with interference and disconnection that can happen with front ports that use cables.

• If your USB WiFi adapter is USB 3 capable then plug it into a USB 3 port.

• Avoid USB 3.1 Gen 2 ports if possible as almost all currently available adapters have been tested with USB 3.1 Gen 1 (aka USB 3) and not with USB 3.1 Gen 2.

• If you use an extension cable and your adapter is USB 3 capable, the cable needs to be USB 3 capable.

• Some USB WiFi adapters require considerable electrical current and push the capabilities of the power available via USB port. One example is devices that use the Realtek 8814au chipset. Using a powered multiport USB extension can be a good idea in cases like this.

How to disable onboard WiFi on Raspberry Pi 3B, 3B+, 3A+, 4B and Zero W.

Add the following line to /boot/config.txt

dtoverlay=disable-wifi

How to forget a saved WiFi network on a Raspberry Pi

1. Edit wpa_supplicant.conf

$ sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

2. Delete the relevant WiFi network block (including the 'network=' and opening/closing braces.

3. Press ctrl-x followed by 'y' and enter to save the file.

4. Reboot