validate cadvisor rootpath

pkg/kubelet/cadvisor/cadvisor_linux.go

@@ -23,6 +23,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
+	"os"
 	"strconv"
 	"time"
 
@@ -105,6 +106,14 @@ func New(address string, port uint, runtime string, rootPath string) (Interface,
 		return nil, err
 	}
 
+	if _, err := os.Stat(rootPath); err != nil {
+		if os.IsNotExist(err) {
+			return nil, fmt.Errorf("rootDirectory %q does not exist", rootPath)
+		} else {
+			return nil, fmt.Errorf("failed to Stat %q: %v", rootPath, err)
+		}
+	}
+
 	cadvisorClient := &cadvisorClient{
 		runtime:  runtime,
 		rootPath: rootPath,