Merge pull request #36474 from bruceauyeung/branch-failure-check-on-umount-when-kubeadm-reset

Automatic merge from submit-queue

add failure check on umount when kubeadm reset, and on service stop

**What this PR does / why we need it**:
before this PR, `umount` will exit with code `123` if `grep` does not match anything
`xargs` has an option:

>-r, --no-run-if-empty
              If the standard input does not contain any nonblanks, do not run the command.  Normally, the command is run  once  even  if
              there is no input.  This option is a GNU extension.


1. this PR add `-r` option to `xargs` , so `umount` will not execute and exit with code `0` correctly while `grep` does not match anything.
2. this PR add failure check on umount. for example, if the directory to be umount is busy, a error message will be printed:
>failed to unmount directories in /var/lib/kubelet, umount: /var/lib/kubelet/foo/bar: target is busy
        (In some cases useful info about processes that
         use the device is found by lsof(8) or fuser(1).)

3. add failure check on kubelet service stop.


Signed-off-by: bruceauyeung <ouyang.qinhua@zte.com.cn>

cmd/kubeadm/app/cmd/reset.go

@@ -124,12 +124,17 @@ func (r *Reset) Run(out io.Writer) error {
 		fmt.Printf("%v", err)
 	} else {
 		fmt.Printf("Stopping the %s service...\n", serviceToStop)
-		initSystem.ServiceStop(serviceToStop)
+		if err := initSystem.ServiceStop(serviceToStop); err != nil {
+			fmt.Printf("failed to stop the %s service", serviceToStop)
+		}
 	}
 
 	fmt.Printf("Unmounting directories in /var/lib/kubelet...\n")
-	// Don't check for errors here, since umount will return a non-zero exit code if there is no directories to umount
-	exec.Command("sh", "-c", "cat /proc/mounts | awk '{print $2}' | grep '/var/lib/kubelet' | xargs umount").Run()
+	umountDirsCmd := "cat /proc/mounts | awk '{print $2}' | grep '/var/lib/kubelet' | xargs -r umount"
+	umountOutputBytes, err := exec.Command("sh", "-c", umountDirsCmd).Output()
+	if err != nil {
+		fmt.Printf("failed to unmount directories in /var/lib/kubelet, %s", string(umountOutputBytes))
+	}
 
 	resetConfigDir("/etc/kubernetes/")