8821cu ( 8821cu.ko ) 🚀

Linux Driver for USB WiFi Adapters that are based on the RTL8811CU, RTL8821CU, RTL8821CUH and RTL8731AU Chipsets

• v5.12.0.4 (Realtek) (20210916) plus updates from the Linux community

Note: Please read "supported-device-IDs" for information about how to confirm that this is the correct driver for your adapter.

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)
• WPA3-SAE (Personal) (see FAQ)
• WPA3-Enterprise (Suite-B 192-bit)
• WAPI 1.0 station mode
• WPS - PIN and PBC Methods
• IEEE 802.11b/g/n/ac Client mode
  • Supports wireless security for WEP, WPA TKIP and WPA2 AES PSK
  • Supports site survey scan and manual connect
  • Supports WPA/WPA2 TLS client
• Power saving modes
• Miracast
• WiFi-Direct
• MU-MIMO
• Mesh
• Wake on WLAN
• Wireshark compatible
• Aircrack-ng compatible
• Packet injection
• hostapd compatible
• AP mode DFS channel support
• Supported interface modes
  • Managed
  • Monitor (see FAQ)
  • AP
  • P2P-client
  • P2P-GO
• Log level control
• LED control
• Power saving control
• VHT control (allows 80 MHz channel width in AP mode)
• AP mode DFS channel control

A FAQ is available at the end of this document.

Additional documentation is in the file 8821cu.conf.

Compatible CPU Architectures

• x86, i686
• x86-64, amd64
• armv6l, armv7l (arm)
• aarch64 (arm64)

Compatible Kernels

• Kernels: 4.19 - 5.11 (Realtek)
• Kernels: 5.12 - 6.2 (community support)

Tested Compilers

• gcc 10, 11 and 12

Tested Linux Distributions

Note: The information in this section depends largely on user reports which can be provided via PR or message in Issues.

• Arch Linux (kernels 5.4 and 5.11)

• Armbian_22.11.1 (kernel 5.15) (Rock 4 SE (Rock 4b image with xfce))

• Debian 11 (kernels 5.10 and 5.15)

• Fedora (kernel 5.11) and Fedora 37 (kernel 6.0)

• Kali Linux (kernel 5.10)

• Manjaro 21.1 (kernel 5.13)

• openSUSE Tumbleweed (rolling) (kernel 5.15)

• Raspberry Pi OS (2022-09-22) (ARM 32 bit and 64 bit) (kernel 5.15)

• Raspberry Pi Desktop (2022-07-01) (x86 32 bit) (kernel 5.10)

• SkiffOS for Odroid XU4 (ARM 32 bit) (kernel 6.0.7)

• Ubuntu 22.04 (kernel 5.15) and 22.10 (kernel 5.19) (kernel 6.2)

• Void Linux (kernel 5.18)

Note: Red Hat Enterprise Linux (RHEL) and distros based on RHEL are not supported due to the way kernel patches are handled. I will support knowledgable RHEL developers if they want to merge the required support and keep it current.

Note: Android is supported in the driver according to Realtek. I will support knowledgable Android developers if they want to merge and keep current the required support (most likely just instructions about how to compile and maybe a modification or two to the Makefile).

Download Locations for Tested Linux Distributions

• Arch Linux
• Armbian
• Debian
• Fedora
• Kali Linux
• Manjaro
• openSUSE
• Raspberry Pi OS
• SkiffOS
• Ubuntu
• Void Linux

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

• EDUP EP-AC1651 (nano) (single-state, single-function)
• EDUP EP-AC1635 (single-state, single-function)
• Numerous adapters that are based on the supported chipset.

Note: If you are looking for information about what adapter to buy, click here and look for Main Menu item 2 which will show information about and links to recommended adapters.

Note: If you decide to buy an adapter that is supported by this driver, I recommend you search for an adapter that is single-state and single-function. Multi-function adapters, wifi and bluetooth, can be problematic. The rtl8821cu chipset is multi-fuction. The rtl8811cu chipset is single-function. For advice about single-state and multi-state adapters. click here and look for Main Menu item 1.

Installation Information

Note: As of Linux kernel 6.2, an in-kernel driver for the chipsets supported by this driver has been included in the Linux kernel. The installation and removal scripts for the driver in this repo automatically deactivate the in-kernel driver on installation and reactivate the in-kernel driver on removal. No special action needs to be taken by users.

Warning: Installing multiple out-of-kernel drivers for the same hardware usually does not end well. If a previous attempt to install this driver failed or if you have previously installed another driver for chipsets supported by this driver, you MUST remove anything that the previous attempt installed BEFORE attempting to install this driver. This driver can be removed with the script called ./remove-driver.sh. Information is available in the section called Removal of the Driver. You can get a good idea as to whether you need to remove a previously installed driver by running the following command:

sudo dkms status

Warning: If you decide to upgrade to a new version of kernel such as 5.15 to 5.19, you need to upgrade the driver you have installed with the newest available before installing the new kernel. Use the following commands in the driver directory:

sudo ./remove-driver.sh

git pull

sudo ./install-driver.sh

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 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).

An alternative terminal is to use SSH (Secure Shell) from the same or from another computer, in which case you will be in a suitable terminal after logging in, but this step requires that an SSH daemon/server has already been configured. (There are lots of SSH guides available, e.g., for the Raspberry Pi and for Ubuntu. Do not forget to secure the SSH server.)

You will need to have sufficient access rights to use sudo so that commands can be executed as the root user. (If the command sudo echo Yes returns "Yes", with or without having to enter your password, you do have sufficient access rights.)

DKMS is used for the installation, if available. DKMS is a system utility which will automatically recompile and reinstall 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.

Secure Boot: The installation script, install-driver.sh, will automatically support secure boot... if your distro supports the method dkms uses. I regularly test the installation script on systems with secure boot on. It works seemlessly on modern Ubuntu based distros as long as secure boot was set up properly during the installation of the operating system. Some distros, such as the Raspberry Pi OS, do not support secure boot because the hardware they support does not support secure boot making it unnecessary to attempt to support it. There are distros that may require additional steps to sign the driver for secure boot operation. Fedora is an example. In installation Step 3, note that openssl must be installed as Fedora does not install it by default. There will also be another step for Fedora after install-driver.sh script is completed. This will be explained in the instructions at the appropriate time. Overall, secure boot requires that openssl and mokutil be installed and that additional steps be performed if necessary. To test if secure boot is the problem: If you install this driver and, after a reboot, the driver is not working, you can go into the BIOS and temporarily turn secure boot off to see if secure boot is the problem.

Installation Steps

Note: The installation instructions are for the novice user. Experienced users are welcome to alter the installation to meet their needs. Support will be provided, on a best effort basis, based on the steps below.

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

Step 2: Update and upgrade system packages (select the option for the distro you are using)

Note: If your Linux distro does not fall into one of options listed below, you will need to research how to update and upgrade your system packages.

• Option for Debian based distributions such as Ubuntu, Kali, Armbian and Raspberry Pi OS

sudo apt update && sudo apt upgrade

• Option for Arch based distributions such as Manjaro

sudo pacman -Syu

• Option for Fedora based distributions

sudo dnf upgrade

• Option for openSUSE based distributions

sudo zypper update

• Option for Void Linux

sudo xbps-install -Syu

Note: It is recommended that you reboot your system at this point. The rest of the installation will appreciate having a fully up to date system to work with. The installation can then be continued with Step 3.

sudo reboot

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

Note: If your Linux distro does not fall into one of options listed below, you will need to research how to properly setup up the development environment for your system.

• Option for Armbian (arm64)

sudo apt install -y build-essential

• Option for Raspberry Pi OS (arm/arm64)

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

• Option for Debian, Kali, and Raspberry Pi Desktop (x86)

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

• Option for Ubuntu (all official flavors) and the numerous Ubuntu based distros

sudo apt install -y build-essential dkms git iw

• Option for Fedora

Note: Installing openssl is only necessary for secure boot support.

sudo dnf -y install git dkms kernel-devel openssl

• Option for openSUSE

sudo zypper install -t pattern devel_kernel dkms

• Option for Alpine

sudo apk add linux-lts-dev make gcc

• Option for Void Linux

sudo xbps-install linux-headers dkms git make

• Options for Arch and Manjaro (if using Manjaro for RasPi4B, see note)

If using pacman

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

Note: The following is needed if using Manjaro for RasPi4B.

sudo pacman -S --noconfirm linux-rpi4-headers dkms git bc

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 install the correct version.

If using other methods, please follow the instructions provided by those methods.

Step 4: Create a directory to hold the downloaded driver

mkdir -p ~/src

Step 5: Move to the newly created directory

cd ~/src

Step 6: Download the driver

git clone https://github.com/morrownr/8821cu-20210916.git

Step 7: Move to the newly created driver directory

cd ~/src/8821cu-20210916

Step 8: Run the installation script (install-driver.sh)

Note: It is recommended that you terminate running apps so as to provide the maximum amount of RAM to the compilation process.

Note: For automated builds (non-interactive), use NoPrompt as an option.

sudo ./install-driver.sh

Note: If you elect to skip the reboot at the end of the installation script, the driver may not load immediately and the driver options will not be applied. Rebooting is strongly recommended.

Note: Fedora users that have secure boot turned on should run the following to enroll the key:

sudo mokutil --import /var/lib/dkms/mok.pub

Manual build instructions: The above script automates the installation process, however, if you want to or need to do a command line installation, use the following:

make clean
make
sudo make install
sudo reboot

Note: If you use the manual build instructions, you will need to repeat the process each time a new kernel is installed in your distro.

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Driver Options (edit-options.sh)

A file called 8821cu.conf will be installed in /etc/modprobe.d by default if you use the ./install-driver.sh script.

Note: The installation script will prompt you to edit the options.

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

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

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Upgrading the Driver

Note: Linux development is continuous therefore work on this driver is continuous.

Note: Upgrading the driver is advised in the following situations:

• if a new or updated version of the driver needs to be installed
• if a distro version upgrade is going to be installed (i.e. going from kernel 5.10 to kernel 5.15)

Step 1: Move to the driver directory

cd ~/src/8821cu-20210916

Step 2: Remove the currently installed driver

sudo ./remove-driver.sh

Step 3: Pull updated code from this repo

git pull

Step 4: Install the driver

sudo ./install-driver.sh

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Removal of the Driver (remove-driver.sh)

Note: Removing the driver is advised in the following situations:

• if driver installation fails
• if the driver is no longer needed

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

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

Step 2: Move to the driver directory

cd ~/src/8821cu-20210916

Step 3: Run the removal script

Note: For automated builds (non-interactive), use NoPrompt as an option.

sudo ./remove-driver.sh

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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 or WPA2/WPA3 mixed or WPA3. Do not set WPA2 mixed mode or WPA or TKIP.

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

• Channels for 2.4 GHz: Set channel 1 or 6 or 11 depending on the congestion at your location. Do not set automatic channel selection. As time passes, if you notice poor performance, recheck congestion and set channel appropriately. The environment around you can and does change over time.

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

• Network names: Do not set the 2.4 GHz Network and the 5 GHz Network to the same name. Note: Unfortunately many routers come with both networks set to the same name. You need to be able to control which network that is in use so changing the name of one of the networks is recommended. Since many IoT devices use the 2.4 GHz network, it may be better to change the name of the 5 GHz network.

• Channels for 5 GHz: Not all devices are capable of using DFS channels (I'm looking at you Roku.) It may be necessary to set a fixed channel in the range of 36 to 48 or 149 to 165 in order for all of your devices to work on 5 GHz. (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. You may have to test to see what the best location is in your environment.

• Check congestion: There are apps available for smart phones that allow you to get an idea of 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.

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Recommendations regarding USB

• Moving your USB WiFi adapter to a different USB port has been known to fix a variety of problems.

• 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.

• If your USB WiFi adapter is USB 3 capable and you want it to operate in USB3 mode, 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 (if not, you will be limited to USB 2 speeds).

• Extention cables can be problematic. A way to check if the extension cable is the problem is to plug the adapter temporarily into a USB port on the computer.

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

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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

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How to forget a saved WiFi network on a Raspberry Pi

Step 1: Edit wpa_supplicant.conf

sudo ${EDITOR} /etc/wpa_supplicant/wpa_supplicant.conf

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

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

Step 4: Reboot

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FAQ

Question: Is WPA3 supported?

Answer: WPA3-SAE is supported. It works well on most modern Linux distros but not all. Generally the reason for WPA3 not working on Linux distros is that the distro has an old version of wpa_supplicant or Network Manager. Your options are to upgrade to a more modern distro (distros released after mid 2022) or compile and install new versions of wpa_supplicant and/or Network Manager.

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Question: I bought two usb wifi adapters based on this chipset and am planning to use both in the same computer. How do I set that up?

Answer: Realtek drivers do not support more than one adapter with the same chipset in the same computer. You can have multiple Realtek based adapters in the same computer as long as the adapters are based on different chipsets.

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Question: Why do you recommend Mediatek based adapters when you maintain this repo for a Realtek driver?

Answer: Many new and existing Linux users already have adapters based on Realtek chipsets. This repo is for Linux users to support their existing adapters but my STRONG recommendation is for Linux users to seek out USB WiFi solutions based on Mediatek chipsets:

https://github.com/morrownr/USB-WiFi

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Question: Will you put volunteers to work?

Answer: Yes. Post a message in Issues or Discussions if interested.

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Question: I am having problems with my adapter and I use Virtualbox?

Answer: This article may help.

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Question: The driver installation script completed successfully and the driver is installed but does not seem to be working. What is wrong?

Answer: Turn secure boot off to see if that allows the driver to work. This driver is primarily tested on Debian based distros such as Ubuntu, Raspberry Pi OS and Kali. In an attempt to make this driver work well on many Linux distros, other distros, including the Arch based Manjaro is used for testing. Currently I do not have installations of Fedora or OpenSUSE available for testing and reply on user reports of success or failure. I have two test systems with secure boot on so as to test secure boot. I have not seen any secure boot problems with Debian based systems and I don't remember problems with Manjaro.

dkms is used in the installation script. It helps with a lot of issues that will come up if a simple manual installation is used. dkms has the capability to handle the needs of secure boot. dkms was written by and is maintained by Dell. Dell has been offering some Ubuntu pre-loaded systems for years so their devs likely test on Ubuntu. I suspect Fedora and OpenSUSE may be handing their secure boot support differently than Debian based systems and this is leading to problems. This and the other repos I have are VERY heavily used and I am sure there are plenty of non-Debian users that use this driver. Are they all turning off secure boot and not reporting the problem? I don't know. What I do know is that reports like this are rare.

For the driver to compile and install correctly but not be available tells me there is likely a key issue. Here is an interesting link regarding Debian systems and secure boot:

https://wiki.debian.org/SecureBoot

That document contains a lot of information that can help an investigation into what the real problem is and I invite you and other Fedora, OpemSUSE and users of other distros that show this problem to investigate and present what you know to the devs of your distro via their problem reporting system. Turning off secure boot is NOT a fix. A real fix needs to happen.

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Question: Can you provide additional information about monitor mode?

Answer: I have a repo that is setup to help with monitor mode:

https://github.com/morrownr/Monitor_Mode

Work to improve monitor mode is ongoing with this driver. Your reports of success or failure are needed. If you have yet to buy an adapter to use with monitor mode, there are adapters available that are known to work very well with monitor mode. My recommendation for those looking to buy an adapter for monitor mode is to buy adapters based on the following chipsets: mt7921au, mt7612u, mt7610u, rtl8812au and rtl8811au. My specific recommendations for adapters in order of preference are:

ALFA AWUS036ACHM - long range - in-kernel driver

ALFA AWUS036ACM - in-kernel driver

ALFA AWUS036ACH - long range - driver

ALFA AWUS036ACS - driver

To ask questions, go to USB-WiFi and post in Discussions or Issues.

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Question: I have an adapter with the 8821cu chipset and it supports bluetooth. The bluetooth works but the wifi does not. What is wrong?

Answer: There appears to be an issue where adapters can be set up differently by makers. The fix is to set the driver option ( rtw_RFE_type ) in 8821cu.conf. The easiest way to edit 8821cu.conf is to run the following from the driver directory:

sudo ./edit-options.sh

Once in the document, you can scroll down to the documentation about rtw_RFE_type. You will likely have to experiment to find out what setting works best for your adapter but a good place to start is probably...

rtw_RFE_type=7

Simply add that option to the end of the options line, save and reboot.

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Contributors:

@Jibun-no-Kage

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