运行roscore时发现，出现错误：
The program 'roscore' is currently not installed. You can install it by typing:
sudo apt install python-roslaunch
按照提示执行sudo apt install python-roslaunch ，会发现出现新的错误。
解决办法1：没有source环境导致
打开 gedit ~/.bashrc
添加 source /opt/ros/kinetic/setup.bash
执行 source ~/.bashrc
运行roscore， 如果能正常运行了，恭喜你，问题解决了。如果还是打印一样的错误信息，则看继续往下看...
解决方法2：安装依赖包
执行 sudo apt install ros-kinetic-roslaunch
所有选项都选择 y
安装结束后，再次执行 source ~/.basnrc
运行 roscore，出现如下信息，表示ros已经正常运行！
... logging to /home/supernode/.ros/log/2d222370-9f71-11ec-8f1d-049226d627d1/roslaunch-supernode-6569.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.
started roslaunch server http://supernode:42653/
ros_comm version 1.12.17
SUMMARY
========
PARAMETERS
* /rosdistro: kinetic
* /rosversion: 1.12.17
NODES
auto-starting new master
process[master]: started with pid [6608]
ROS_MASTER_URI=http://supernode:11311/
setting /run_id to 2d222370-9f71-11ec-8f1d-049226d627d1
process[rosout-1]: started with pid [6629]
started core service [/rosout]