kubeadm: prompt for confirmation when resetting a master

cmd/kubeadm/app/cmd/cmd.go

@@ -32,7 +32,7 @@ import (
 )
 
 // NewKubeadmCommand return cobra.Command to run kubeadm command
-func NewKubeadmCommand(_ io.Reader, out, err io.Writer) *cobra.Command {
+func NewKubeadmCommand(in io.Reader, out, err io.Writer) *cobra.Command {
 	cmds := &cobra.Command{
 		Use:   "kubeadm",
 		Short: "kubeadm: easily bootstrap a secure Kubernetes cluster",
@@ -77,7 +77,7 @@ func NewKubeadmCommand(_ io.Reader, out, err io.Writer) *cobra.Command {
 	cmds.AddCommand(NewCmdConfig(out))
 	cmds.AddCommand(NewCmdInit(out))
 	cmds.AddCommand(NewCmdJoin(out))
-	cmds.AddCommand(NewCmdReset(out))
+	cmds.AddCommand(NewCmdReset(in, out))
 	cmds.AddCommand(NewCmdVersion(out))
 	cmds.AddCommand(NewCmdToken(out, err))
 	cmds.AddCommand(upgrade.NewCmdUpgrade(out))

cmd/kubeadm/app/cmd/reset.go

@@ -17,6 +17,8 @@ limitations under the License.
 package cmd
 
 import (
+	"bufio"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -44,11 +46,12 @@ var (
 )
 
 // NewCmdReset returns the "kubeadm reset" command
-func NewCmdReset(out io.Writer) *cobra.Command {
+func NewCmdReset(in io.Reader, out io.Writer) *cobra.Command {
 	var skipPreFlight bool
 	var certsDir string
 	var criSocketPath string
 	var ignorePreflightErrors []string
+	var forceReset bool
 
 	cmd := &cobra.Command{
 		Use:   "reset",
@@ -57,7 +60,7 @@ func NewCmdReset(out io.Writer) *cobra.Command {
 			ignorePreflightErrorsSet, err := validation.ValidateIgnorePreflightErrors(ignorePreflightErrors, skipPreFlight)
 			kubeadmutil.CheckErr(err)
 
-			r, err := NewReset(ignorePreflightErrorsSet, certsDir, criSocketPath)
+			r, err := NewReset(in, ignorePreflightErrorsSet, forceReset, certsDir, criSocketPath)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(r.Run(out))
 		},
@@ -83,6 +86,11 @@ func NewCmdReset(out io.Writer) *cobra.Command {
 		"The path to the CRI socket to use with crictl when cleaning up containers.",
 	)
 
+	cmd.PersistentFlags().BoolVar(
+		&forceReset, "force", false,
+		"Reset the node without prompting for confirmation.",
+	)
+
 	return cmd
 }
 
@@ -93,9 +101,21 @@ type Reset struct {
 }
 
 // NewReset instantiate Reset struct
-func NewReset(ignorePreflightErrors sets.String, certsDir, criSocketPath string) (*Reset, error) {
-	glog.Infoln("[preflight] running pre-flight checks")
+func NewReset(in io.Reader, ignorePreflightErrors sets.String, forceReset bool, certsDir, criSocketPath string) (*Reset, error) {
+	if !forceReset {
+		fmt.Println("[reset] WARNING: changes made to this host by 'kubeadm init' or 'kubeadm join' will be reverted.")
+		fmt.Print("[reset] are you sure you want to proceed? [y/N]: ")
+		s := bufio.NewScanner(in)
+		s.Scan()
+		if err := s.Err(); err != nil {
+			return nil, err
+		}
+		if s.Text() != "y" {
+			return nil, errors.New("Aborted reset operation")
+		}
+	}
 
+	glog.Infoln("[preflight] running pre-flight checks")
 	if err := preflight.RunRootCheckOnly(ignorePreflightErrors); err != nil {
 		return nil, err
 	}

cmd/kubeadm/app/cmd/reset_test.go

@@ -56,28 +56,31 @@ func assertDirEmpty(t *testing.T, path string) {
 }
 
 func TestNewReset(t *testing.T) {
+	var in io.Reader
 	certsDir := kubeadmapiext.DefaultCertificatesDir
 	criSocketPath := "/var/run/dockershim.sock"
 	skipPreFlight := false
+	forceReset := true
 
 	ignorePreflightErrors := []string{"all"}
 	ignorePreflightErrorsSet, _ := validation.ValidateIgnorePreflightErrors(ignorePreflightErrors, skipPreFlight)
-	NewReset(ignorePreflightErrorsSet, certsDir, criSocketPath)
+	NewReset(in, ignorePreflightErrorsSet, forceReset, certsDir, criSocketPath)
 
 	ignorePreflightErrors = []string{}
 	ignorePreflightErrorsSet, _ = validation.ValidateIgnorePreflightErrors(ignorePreflightErrors, skipPreFlight)
-	NewReset(ignorePreflightErrorsSet, certsDir, criSocketPath)
+	NewReset(in, ignorePreflightErrorsSet, forceReset, certsDir, criSocketPath)
 }
 
 func TestNewCmdReset(t *testing.T) {
 	var out io.Writer
-	cmd := NewCmdReset(out)
+	var in io.Reader
+	cmd := NewCmdReset(in, out)
 
 	tmpDir, err := ioutil.TempDir("", "kubeadm-reset-test")
 	if err != nil {
 		t.Errorf("Unable to create temporary directory: %v", err)
 	}
-	args := []string{"--ignore-preflight-errors=all", "--cert-dir=" + tmpDir}
+	args := []string{"--ignore-preflight-errors=all", "--cert-dir=" + tmpDir, "--force"}
 	cmd.SetArgs(args)
 	if err := cmd.Execute(); err != nil {
 		t.Errorf("Cannot execute reset command: %v", err)