Here is how to manually restart or stop Virtuoso from the command line.
The following article was used as a reference.
https://stackoverflow.com/questions/42575039/how-to-manually-restart-or-stop-virtuoso-from-commandline
The following approach seems to work well.
A specific example is as follows.
If isql is not found as shown below, change the path and execute.
I hope this serves as a helpful reference.