diff --git a/main.go b/main.go
index 8bbdf6a..fef5833 100644
--- a/main.go
+++ b/main.go
@@ -78,7 +78,12 @@ func main() {
 		log.Info("todo: add flag to ignore. for now, fix problems in the config file.")
 		os.Exit(0)
 	}
-	newe := ValidateDiskFilenames(me.cluster)
+	newe, err := ValidateDiskFilenames(me.cluster)
+	if err != nil {
+		log.Info(err)
+		os.Exit(-1)
+	}
+	// this is a new droplet. add it to the cluster
 	for _, e := range newe {
 		newEvents = append(newEvents, e)
 	}
diff --git a/validate.go b/validate.go
index 4105c6f..42c9ab6 100644
--- a/validate.go
+++ b/validate.go
@@ -17,6 +17,7 @@ import (
 	"errors"
 	"fmt"
 	"path/filepath"
+	"strings"
 
 	"github.com/google/uuid"
 
@@ -102,10 +103,11 @@ func ValidateUniqueFilenames(cluster *pb.Cluster) bool {
 	return ok
 }
 
-func ValidateDiskFilenames(cluster *pb.Cluster) []*pb.Event {
+func ValidateDiskFilenames(cluster *pb.Cluster) ([]*pb.Event, error) {
 	var alle []*pb.Event
 
 	for _, d := range cluster.Droplets {
+		var found bool = false
 		for _, disk := range d.Disks {
 			filename := disk.Filename
 			filebase := filepath.Base(filename)
@@ -117,6 +119,20 @@ func ValidateDiskFilenames(cluster *pb.Cluster) []*pb.Event {
 				alle = append(alle, e)
 				disk.Filename = filebase
 			}
+			// make sure the filename is the hostname + .qcow2
+			filetype := filepath.Ext(filebase)
+			if filetype == ".img" {
+				found = true
+				continue
+			}
+			if filetype != ".qcow2" {
+				log.Info("file type", filetype, "not supported for", filebase, "on", d.Hostname)
+				return nil, errors.New("only supporting qcow2 images for now")
+			}
+			test := strings.TrimSuffix(filebase, filetype)
+			if test == d.Hostname {
+				found = true
+			}
 			if dir == "." {
 				continue
 			}
@@ -130,8 +146,12 @@ func ValidateDiskFilenames(cluster *pb.Cluster) []*pb.Event {
 				disk.Filepath = dir
 			}
 		}
+		if !found {
+			log.Info("droplet", d.Hostname, d.Disks)
+			return nil, errors.New("droplet " + d.Hostname + " has nonstandard disk names")
+		}
 	}
-	return alle
+	return alle, nil
 }
 
 func getNewMac() string {