Merge pull request #65354 from hanxiaoshuai/fix06222

Automatic merge from submit-queue (batch tested with PRs 65349, 65354, 65402). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

fixtodo: Move these kubelet start/stop functions to phases/kubelet

**What this PR does / why we need it**:
fixtodo: Move these kubelet start/stop functions to phases/kubelet
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
NONE
```

cmd/kubeadm/app/phases/kubelet/BUILD

@@ -6,6 +6,7 @@ go_library(
         "config.go",
         "dynamic.go",
         "flags.go",
+        "kubelet.go",
     ],
     importpath = "k8s.io/kubernetes/cmd/kubeadm/app/phases/kubelet",
     visibility = ["//visibility:public"],
@@ -19,6 +20,7 @@ go_library(
         "//pkg/apis/rbac/v1:go_default_library",
         "//pkg/kubelet/apis/kubeletconfig/scheme:go_default_library",
         "//pkg/kubelet/apis/kubeletconfig/v1beta1:go_default_library",
+        "//pkg/util/initsystem:go_default_library",
         "//pkg/util/node:go_default_library",
         "//pkg/util/procfs:go_default_library",
         "//pkg/util/version:go_default_library",

cmd/kubeadm/app/phases/kubelet/kubelet.go

@@ -0,0 +1,63 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package kubelet
+
+import (
+	"fmt"
+
+	"k8s.io/kubernetes/pkg/util/initsystem"
+)
+
+// TryStartKubelet attempts to bring up kubelet service
+func TryStartKubelet() {
+	// If we notice that the kubelet service is inactive, try to start it
+	initSystem, err := initsystem.GetInitSystem()
+	if err != nil {
+		fmt.Println("[preflight] no supported init system detected, won't make sure the kubelet is running properly.")
+		return
+	}
+
+	if !initSystem.ServiceExists("kubelet") {
+		fmt.Println("[preflight] couldn't detect a kubelet service, can't make sure the kubelet is running properly.")
+	}
+
+	fmt.Println("[preflight] Activating the kubelet service")
+	// This runs "systemctl daemon-reload && systemctl restart kubelet"
+	if err := initSystem.ServiceRestart("kubelet"); err != nil {
+		fmt.Printf("[preflight] WARNING: unable to start the kubelet service: [%v]\n", err)
+		fmt.Printf("[preflight] please ensure kubelet is reloaded and running manually.\n")
+	}
+}
+
+// TryStopKubelet attempts to bring down the kubelet service momentarily
+func TryStopKubelet() {
+	// If we notice that the kubelet service is inactive, try to start it
+	initSystem, err := initsystem.GetInitSystem()
+	if err != nil {
+		fmt.Println("[preflight] no supported init system detected, won't make sure the kubelet not running for a short period of time while setting up configuration for it.")
+		return
+	}
+
+	if !initSystem.ServiceExists("kubelet") {
+		fmt.Println("[preflight] couldn't detect a kubelet service, can't make sure the kubelet not running for a short period of time while setting up configuration for it.")
+	}
+
+	// This runs "systemctl daemon-reload && systemctl stop kubelet"
+	if err := initSystem.ServiceStop("kubelet"); err != nil {
+		fmt.Printf("[preflight] WARNING: unable to stop the kubelet service momentarily: [%v]\n", err)
+	}
+}