Update README.md

README.md

 To grant permissions to the USB device, the udev system can be employed:
 
  * `echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="04d8", ATTR{idProduct}=="0100", MODE="0666"' | sudo tee /etc/udev/rules.d/60-kromek-radangel.rules`
- * `udevadm control --reload-rules && udevadm trigger`
+ * `sudo udevadm control --reload-rules && sudo udevadm trigger`
 
-Compiling the radangel binary for the linux operating system is easy:
-Just run `make` in the `src` directory or
+Compiling the radangel binary for the linux operating system requires to install some dependencies in advance. To install the build dependencies on a Debian system the apt-get command can be used:
 
-`gcc -std=gnu99 -Wall radangel.c -o radangel -pthread -lm -lhidapi-libusb`
+* `apt-get update && apt-get -y install build-essential libc6-dev libhidapi-dev`
+
+Then you have two options, to compile the binaryJust run `make` in the `src` directory or
+
+* run `make` in the `src` directory or
+
+* run `gcc -std=gnu99 -Wall radangel.c -o radangel -pthread -lm -lhidapi-libusb` in the `src` directory
 
 The output of the `radangel` daemon consists of two files (time series and histogram):
 
 *  `datasrc.service` systemd unit employs `inotail` to monitor the output files and streams the changes with `socat` into a tcp socket.
 *  `websockify.service` launches the `websockify` daemon which provides the websocket endpoint behind `nginx` webserver (see `nginx-datasrc-location.conf`) and translates between websocket and the plain tcp socket.
 
+Again we need to satisfy the dependencies, e.g. on a Debian system with `apt-get`
+
+* `apt-get update && apt-get -y install build-essential libc6-dev libssl-dev`
+
 To compile the `websockify` daemon just run `make` in the `src/contrib` directory.
 
 The web interface itself uses [Plotly.js](https://plot.ly/javascript/) to display the histogram of the channels in realtime by connecting to the websocket endpoint and provides a convenient user interface for exploring the details of the gamma-spectrum.