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.

Supported 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) (see Monitor_Mode)
  • AP (see Bridged Wireless Access Point)
  • 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

Not supported

• hcxdumptool

A FAQ is available in this repo with the name FAQ.md

• Please read the FAQ and this document before posting issues.

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 - 6.4 (community support)

Tested Compilers

• gcc 9, 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 (kernel 5.15) (Rock 4 SE (Rock 4b image with xfce))

• Debian (kernels 5.10, 5.15 and 6.1)

• Fedora Fedora 38 (6.2.13-300)

• Kali Linux (kernel 5.10)

• Manjaro (kernel 5.13)

• openSUSE Tumbleweed (rolling) (kernel 5.15)

• Raspberry Pi OS (2023-02-21) (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. I reserve the right to delete this support if it causes any problems.

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).

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 chipsets

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. The install-driver.sh script has the capability to detect and remove many conflicting drivers but not all. If this driver does not work well after installation and you have previously installed a driver that you did not remove, it is suggested that you run the following command in an effort to determine if you need to take action to manually remove conflicting drivers:

sudo dkms status

Warning: If you decide to do a distro upgrade, which will likely install a new version of kernel such as 5.15 to 6.1, you need to upgrade this driver with the newest available code before performing the disto upgrade. Use the following commands in the driver directory:

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: see FAQ.

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. General guidance follows.

Development Environment Requirements: (package names may vary by distro)

• Mandatory packages: gcc make bc kernel-headers build-essential git
• Highly recommended packages: dkms rfkill iw ip
• Mandatory packages if Secure Boot is active: openssl sign-file mokutil

Note: The below options should take care of the mandatory and highly recommended requirements. If Secure Boot is active on your system, please also install the mandatory packages for Secure Boot as shown above.

• 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

sudo dnf -y install git dkms kernel-devel

• 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 iw

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

or

sudo sh 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 may need to run the following to enroll the key:

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

Manual Installation Instructions

Note: The above installation steps automate the installation process, however, if you want to or need to do a basic command line installation, use the following:

make clean

make

If secure boot is off:

sudo make install

sudo reboot

If secure boot is on:

Note: Please read to the end of this section before coming back here to enter commands.

sudo make sign-install

You will be promted for a password, please remember the password as it will be used in some of the following steps.

sudo reboot

The MOK managerment screen will appear during boot:

`Shim UEFI Key Management"

Press any key...

Select "Enroll key"

Select "Continue"

Select "Yes"

When promted, enter the password you entered earlier.

If you enter the wrong password, your computer will not be bootable. In this case, use the BOOT menu from your BIOS to boot then as follows:

sudo mokutil --reset

Restart your computer and use the BOOT menu from BIOS to boot. In the MOK managerment screen, select reset MOK list. Then Reboot and retry from the step sudo make sign-install.

To remove the driver if installed by the manual installation instructions:

sudo make uninstall

sudo reboot

Note: If you use the manual installation 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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Contributors:

@Jibun-no-Kage
@alkisg
@M0les
@mendel5
@colincdean
@jeff-hiner
@paralin
@tamojitray
@amisix
@henkv1
@SubZero5

Without the above contributors, this driver would not be nearly as good as it.

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To-Do:

• Detect and alert users when Airplane Mode is on.
• Test for installation in VM's.
• Reduce the size of the README while keeping the needed information.
• Optimize scripts.

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Go to Main Menu

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