handle first disk initialize

Signed-off-by: Songpon Srisawai <songpon.ssw@gmail.com>

Author: songponssw

pkg/instance/start.go

@@ -389,9 +389,19 @@ func ShowMessage(inst *store.Instance) error {
 }
 
 // prepareDiffDisk checks the disk size difference between inst.Disk and yaml.Disk.
+// If there is no diffDisk, return nil (the instance has not been initialized or started yet).
 func prepareDiffDisk(inst *store.Instance) error {
 	diffDisk := filepath.Join(inst.Dir, filenames.DiffDisk)
 
+	// Handle the instance initialzation 
+	_, err := os.Stat(diffDisk)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+
 	f, err := os.Open(diffDisk)
 	if err != nil {
 		return err