Ian mentioned the rstudio-server and rstudio-server-version commands should be run from your shell.
It would give a result something like this:
username@servername:~/projects/myRproj$ rstudio-server
$Usage: rstudio-server {status|start|stop|restart|test-config|verify-installation|
suspend-session|suspend-all|force-suspend-session|force-suspend-all|
kill-session|kill-all|offline|online|active-sessions|version}
username@servername:~/projects/myRproj$ rstudio-server version
1.1.442 (Professional)
You mentioned that you're just getting some AWS instances up and running for a classroom, is that right?
Can you reset it and start anew?