Tricky Tips Debian: Installing Realtek RTL8811CU/RTL8821CU (Other possibility)

 

Installing Realtek RTL8811CU/RTL8821CU USB wifi adapter driver version 5.4.1 for Linux 4.4.x up to 5.x

I got also this link for another wifi hitspot installation.

First, clone this repository

mkdir -p ~/build
cd ~/build
git clone https://github.com/brektrou/rtl8821CU.git 

Build and install with DKMS

 Debian/Ubuntu:

sudo apt-get install dkms

Plug your USB-wifi-adapter into your PC

If wifi can be detected, congratulations. If not, maybe you need to switch your device usb mode by the following steps in terminal:

1. find your usb-wifi-adapter device ID, like "0bda:1a2b", by type:

lsusb

2. switch the mode by type: (the device ID must be yours.)

Need install usb_modeswitch (Archlinux: sudo pacman -S usb_modeswitch)

sudo usb_modeswitch -KW -v 0bda -p 1a2b
systemctl start bluetooth.service - starting Bluetooth service if it's in inactive state

Make it permanent

If steps above worked fine and in order to avoid periodically having to make usb_modeswitch you can make it permanent (Working in Ubuntu 18.04 LTS):

1. Edit usb_modeswitch rules:

   sudo nano /lib/udev/rules.d/40-usb_modeswitch.rules

2. Append before the end line LABEL="modeswitch_rules_end" the following:

   # Realtek 8211CU Wifi AC USB
   ATTR{idVendor}=="0bda", ATTR{idProduct}=="1a2b", RUN+="/usr/sbin/usb_modeswitch -K -v 0bda -p 1a2b" 

   Make sure to set your ATTR{idVendor} and the -v argument to the left portion of the output of lsusb device ID, and your ATTR{idProduct} and -p argument to the right portion of the lsusb device ID. For example (for the Cudy AC600 usb wifi adapter) the output from lsusb command looks like this:

   Bus 001 Device 016: ID 0bda:c811 Realtek Semiconductor Corp. 802.11ac NIC
   

   then your configuration in /lib/udev/rules.d/40-usb_modeswitch.rules should be

   # Realtek 8211CU Wifi AC USB ATTR{idVendor}=="0bda", ATTR{idProduct}=="c811", RUN+="/usr/sbin/usb_modeswitch -K -v 0bda -p c811"

   Checking installed driver

   If you successfully install the driver, the driver is installed on /lib/modules/<linux version>/kernel/drivers/net/wireless/realtek/rtl8821cu. Check the driver with the ls command:

   ls /lib/modules/$(uname -r)/kernel/drivers/net/wireless/realtek/rtl8821cu
   

   Make sure 8821cu.ko file present on that directory

   Check with DKMS (if installing via DKMS):

   sudo dkms status

   Monitor mode

   Use the tool 'iw', please don't use other tools like 'airmon-ng'

   Check the OS

   uname -r 

   Sources: https://github.com/brektrou/rtl8821CU 

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