Show error when no scannable servers are detected.

commands/configtest.go

@@ -150,7 +150,10 @@ func (p *ConfigtestCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interfa
 	}
 
 	Log.Info("Detecting Server/Contianer OS... ")
-	scan.InitServers(Log)
+	if err := scan.InitServers(Log); err != nil {
+		Log.Errorf("Failed to init servers: %s", err)
+		return subcommands.ExitFailure
+	}
 
 	Log.Info("Checking sudo configuration... ")
 	if err := scan.CheckIfSudoNoPasswd(Log); err != nil {

commands/prepare.go

@@ -138,7 +138,10 @@ func (p *PrepareCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{
 	logger := util.NewCustomLogger(c.ServerInfo{})
 
 	logger.Info("Detecting OS... ")
-	scan.InitServers(logger)
+	if err := scan.InitServers(logger); err != nil {
+		logger.Errorf("Failed to init servers: %s", err)
+		return subcommands.ExitFailure
+	}
 
 	logger.Info("Checking sudo configuration... ")
 	if err := scan.CheckIfSudoNoPasswd(logger); err != nil {
@@ -154,6 +157,5 @@ func (p *PrepareCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{
 		return subcommands.ExitFailure
 	}
 
-	logger.Info("Success")
 	return subcommands.ExitSuccess
 }

commands/scan.go

@@ -368,7 +368,10 @@ func (p *ScanCmd) Execute(_ context.Context, f *flag.FlagSet, _ ...interface{})
 	}
 
 	Log.Info("Detecting Server/Contianer OS... ")
-	scan.InitServers(Log)
+	if err := scan.InitServers(Log); err != nil {
+		Log.Errorf("Failed to init servers: %s", err)
+		return subcommands.ExitFailure
+	}
 
 	Log.Info("Checking sudo configuration... ")
 	if err := scan.CheckIfSudoNoPasswd(Log); err != nil {

scan/serverapi.go

@@ -170,11 +170,15 @@ func PrintSSHableServerNames() {
 }
 
 // InitServers detect the kind of OS distribution of target servers
-func InitServers(localLogger *logrus.Entry) {
+func InitServers(localLogger *logrus.Entry) error {
 	Log = localLogger
 	servers = detectServerOSes()
+	if len(servers) == 0 {
+		return fmt.Errorf("No scannable servers")
+	}
 	containers := detectContainerOSes()
 	servers = append(servers, containers...)
+	return nil
 }
 
 func detectServerOSes() (sshAbleOses []osTypeInterface) {