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

Before build this driver make sure `make`, `gcc`, `linux-header` and `git` have been installed.

## First, clone this repository
```
mkdir -p ~/build
cd ~/build
git clone https://github.com/brektrou/rtl8821CU.git
```
## Check the name of the interface

Check the interface name of your wifi adapter using 'ifconfig'. Usually, it will be wlan0 by default, but it may vary depends on the kernel and your device. On Ubuntu, for example, it may be named as wlx + MAC address. (https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/) 

If this is the case, you can either disable the feature following the link above, or replace the name used in the driver by

、、、
grep -lr . | xargs sed -i '' -e '/ifcfg-wlan0/!s/wlan0/<name of the device>/g'
、、、

## Build and install with DKMS

DKMS is a system which will automatically recompile and install a kernel module when a new kernel gets installed or updated. To make use of DKMS, install the dkms package.

### Debian/Ubuntu:
```
sudo apt-get install dkms
```
### Arch Linux/Manjaro:
```
sudo pacman -S dkms
```
To make use of the **DKMS** feature with this project, just run:
```
./dkms-install.sh
```
If you later on want to remove it, run:
```
./dkms-remove.sh
```

### 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
```

It should work.

## Build and install without DKMS
Use following commands:
```
cd ~/build/rtl8821CU
make
sudo make install
```
If you later on want to remove it, do the following:
```
cd ~/build/rtl8821CU
sudo make uninstall
```
## 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
``
### ARM architecture tweak for this driver (this solves compilation problem of this driver):
```
sudo cp /lib/modules/$(uname -r)/build/arch/arm/Makefile /lib/modules/$(uname -r)/build/arch/arm/Makefile.$(date +%Y%m%d%H%M)
sudo sed -i 's/-msoft-float//' /lib/modules/$(uname -r)/build/arch/arm/Makefile
sudo ln -s /lib/modules/$(uname -r)/build/arch/arm /lib/modules/$(uname -r)/build/arch/armv7l
```
### Monitor mode
Use the tool 'iw', please don't use other tools like 'airmon-ng'
```
iw dev wlan0 set monitor none
```