Update README.md

Update a workaround for predictable network interface names on Ubuntu

README.md

@@ -8,6 +8,16 @@ 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.
@@ -81,3 +91,4 @@ Use the tool 'iw', please don't use other tools like 'airmon-ng'
 ```
 iw dev wlan0 set monitor none
 ```
+