(base) lu@lu:~$ roscore
... logging to /home/lu/.ros/log/8f30dde8-9c3b-11f0-82d4-d558dad04297/roslaunch-lu-32414.log
Checking log directory for disk usage. This may take a while.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.
RLException: Invalid <param> tag: Cannot load command parameter [rosversion]: command [['rosversion', 'roslaunch']] returned with code [1].
Param xml is <param name="rosversion" command="rosversion roslaunch"/>
The traceback for the exception was written to the log file