I did exactly the following but didn't manage to create a workspace:

erle@erle-brain:~ $ source /opt/ros/kinetic/setup.bash 
erle@erle-brain:~ $ export | grep ROS
declare -x ROSLISP_PACKAGE_DIRECTORIES=""
declare -x ROS_DISTRO="kinetic"
declare -x ROS_ETC_DIR="/opt/ros/kinetic/etc/ros"
declare -x ROS_MASTER_URI="http://localhost:11311"
declare -x ROS_PACKAGE_PATH="/opt/ros/kinetic/share"
declare -x ROS_ROOT="/opt/ros/kinetic/share/ros"
erle@erle-brain:~ $ mkdir catkin_ws
erle@erle-brain:~ $ cd catkin_ws/
erle@erle-brain:~/catkin_ws $ mkdir src
erle@erle-brain:~/catkin_ws $ ls src
erle@erle-brain:~/catkin_ws $ cd src/
erle@erle-brain:~/catkin_ws/src $ catkin_init_workspace 

Creating symlink
"/home/erle/catkin_ws/src/CMakeLists.txt" pointing to "/opt/ros/kinetic/share/catkin/cmake/toplevel.cmake"

erle@erle-brain:~/catkin_ws/src $ ls
CMakeLists.txt
erle@erle-brain:~/catkin_ws/src $ cd ..
erle@erle-brain:~/catkin_ws $ ls
src
erle@erle-brain:~/catkin_ws $ catkin_make
Base path: /home/erle/catkin_ws
Source space: /home/erle/catkin_ws/src
Build space: /home/erle/catkin_ws/build
Devel space: /home/erle/catkin_ws/devel
Install space: /home/erle/catkin_ws/install

Running command: "cmake
/home/erle/catkin_ws/src
-DCATKIN_DEVEL_PREFIX=/home/erle/catkin_ws/devel
-DCMAKE_INSTALL_PREFIX=/home/erle/catkin_ws/install
-G Unix Makefiles" in "/home/erle/catkin_ws/build"

Failed command '['cmake',
'/home/erle/catkin_ws/src',
'-DCATKIN_DEVEL_PREFIX=/home/erle/catkin_ws/devel',
'-DCMAKE_INSTALL_PREFIX=/home/erle/catkin_ws/install', '-G', 'Unix Makefiles']': 
[Errno 2] No such file or directory

what is the problem here? Can you help please?