Sometimes when you first use ROS in the computer in the computer room, just remember to input this command:
source /opt/ros/kinetic/setup.bash
in this case, you can input roscd and rospack, which will work now
After catkin_make, remember to:
source devel/setup.bash
Every time you create a package, remember to
catkin build
source devel/setup.bash
Every time you do some modification in a package, remember come back to the catkin_ws to
source devel/setup.bash
Sometimes when you first use ROS in the computer in the computer room, just remember to input this command: source /opt/ros/kinetic/setup.bash
in this case, you can input roscd and rospack, which will work now
After catkin_make, remember to: source devel/setup.bash
Every time you create a package, remember to catkin build source devel/setup.bash Every time you do some modification in a package, remember come back to the catkin_ws to source devel/setup.bash