install: print usage on invalid options

install.pl

@@ -97,7 +97,8 @@ my $models = {
 
 my $options = {};
 
-GetOptions($options, qw(update cron help|h|?));
+GetOptions($options, qw(update cron help|h|?))
+  or usage();
 
 if ($options->{usage} || (@ARGV != 1 && !$options->{cron})) {
     usage();