fix[close #280]: /tmp becomes readonly when running out of space duri…

…ng operation

core/oci.go

@@ -137,6 +137,39 @@ func OciExportRootFs(buildImageName string, imageRecipe *ImageRecipe, transDir s
 		return err
 	}
 
+	// check if there is enough space in dest to copy the image
+	mountDirStat, err := os.Stat(mountDir)
+	if err != nil {
+		PrintVerboseErr("OciExportRootFs", 8.1, err)
+		return
+	}
+
+	var mountDirSize int64
+	if mountDirStat.IsDir() {
+		mountDirSize, err = getDirSize(mountDir)
+		if err != nil {
+			PrintVerboseErr("OciExportRootFs", 8.2, err)
+			return
+		}
+	} else {
+		mountDirSize = mountDirStat.Size()
+	}
+
+	var stat syscall.Statfs_t
+	err = syscall.Statfs(dest, &stat)
+	if err != nil {
+		PrintVerboseErr("OciExportRootFs", 8.3, err)
+		return
+	}
+
+	availableSpace := stat.Bavail * uint64(stat.Bsize)
+
+	if uint64(mountDirSize) > availableSpace {
+		err := errors.New("not enough space in disk")
+		PrintVerboseErr("OciExportRootFs", 8.4, err)
+		return
+	}
+
 	// copy mount dir contents to dest
 	err = rsyncCmd(mountDir+"/", dest, []string{"--delete", "--checksum"}, false)
 	if err != nil {

core/utils.go

@@ -122,3 +122,29 @@ func isDeviceLUKSEncrypted(devicePath string) (bool, error) {
 
 	return true, nil
 }
+
+// getDirSize calculates the total size of a directory recursively.
+// FIXME: find a way to avoid using du and any other external command
+//		  the walk function in the os package can be used to calculate the size
+//		  of a directory but it needs a solid implementation for links
+func getDirSize(path string) (int64, error) {
+	cmd := exec.Command("du", "-s", "-b", path)
+	var out bytes.Buffer
+	cmd.Stdout = &out
+	err := cmd.Run()
+	if err != nil {
+		return 0, err
+	}
+
+	output := strings.Fields(out.String())
+	if len(output) == 0 {
+		return 0, errors.New("failed to get directory size")
+	}
+
+	size, err := strconv.ParseInt(output[0], 10, 64)
+	if err != nil {
+		return 0, err
+	}
+
+	return size, nil
+}