It would be nice if the netscript bootoption exports an environment variable 
that could be used for checking whether the script is being executed under the 
netscript bootoption or manually. (I've deployment scripts that set up 
harddisks, the script should be executed if running under the netscript 
bootoption but shouldn't be executed by default if invoked manually. Checking 
for $SHLVL is possible but not reliable enough.)