From e42eb28500e2014e7abb7a7bb275f1917db87be7 Mon Sep 17 00:00:00 2001
From: Alexander Kanevskiy <alexander.kanevskiy@intel.com>
Date: Wed, 1 Nov 2017 16:40:13 +0200
Subject: [PATCH] Implement individual control for kubeadm preflight checks

With new flag `--ignore-checks-errors` user is able to
decrease severity of each individual check to warning.

Old flag `--skip-preflight-checks` now acts as
`--ignore-checks-errors=all` and will produce warnings.

Fixes: kubernetes/kubeadm#480
---
 cmd/kubeadm/app/apis/kubeadm/validation/BUILD |   1 +
 .../app/apis/kubeadm/validation/validation.go |  27 ++-
 .../kubeadm/validation/validation_test.go     |  29 +++
 cmd/kubeadm/app/cmd/init.go                   |  34 +--
 cmd/kubeadm/app/cmd/join.go                   |  36 ++--
 cmd/kubeadm/app/cmd/phases/BUILD              |   1 +
 cmd/kubeadm/app/cmd/phases/preflight.go       |   5 +-
 cmd/kubeadm/app/cmd/reset.go                  |  26 ++-
 cmd/kubeadm/app/cmd/reset_test.go             |   4 +
 cmd/kubeadm/app/cmd/upgrade/BUILD             |   2 +
 cmd/kubeadm/app/cmd/upgrade/apply.go          |   7 +-
 cmd/kubeadm/app/cmd/upgrade/common.go         |  10 +-
 cmd/kubeadm/app/cmd/upgrade/plan.go           |   6 +-
 cmd/kubeadm/app/cmd/upgrade/upgrade.go        |   6 +
 cmd/kubeadm/app/preflight/BUILD               |   2 +
 cmd/kubeadm/app/preflight/checks.go           | 195 ++++++++++++++++--
 cmd/kubeadm/app/preflight/checks_test.go      |  19 +-
 17 files changed, 332 insertions(+), 78 deletions(-)

diff --git a/cmd/kubeadm/app/apis/kubeadm/validation/BUILD b/cmd/kubeadm/app/apis/kubeadm/validation/BUILD
index 1c5508fcab..ad9b8936a9 100644
--- a/cmd/kubeadm/app/apis/kubeadm/validation/BUILD
+++ b/cmd/kubeadm/app/apis/kubeadm/validation/BUILD
@@ -33,6 +33,7 @@ go_library(
         "//pkg/registry/core/service/ipallocator:go_default_library",
         "//pkg/util/node:go_default_library",
         "//vendor/github.com/spf13/pflag:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/validation:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/validation/field:go_default_library",
     ],
diff --git a/cmd/kubeadm/app/apis/kubeadm/validation/validation.go b/cmd/kubeadm/app/apis/kubeadm/validation/validation.go
index e54416e8b0..65787dc5cf 100644
--- a/cmd/kubeadm/app/apis/kubeadm/validation/validation.go
+++ b/cmd/kubeadm/app/apis/kubeadm/validation/validation.go
@@ -26,6 +26,7 @@ import (
 
 	"github.com/spf13/pflag"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/validation"
 	"k8s.io/apimachinery/pkg/util/validation/field"
 	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
@@ -289,7 +290,7 @@ func ValidateMixedArguments(flag *pflag.FlagSet) error {
 
 	mixedInvalidFlags := []string{}
 	flag.Visit(func(f *pflag.Flag) {
-		if f.Name == "config" || strings.HasPrefix(f.Name, "skip-") || f.Name == "dry-run" || f.Name == "kubeconfig" {
+		if f.Name == "config" || strings.HasPrefix(f.Name, "ignore-checks-") || strings.HasPrefix(f.Name, "skip-") || f.Name == "dry-run" || f.Name == "kubeconfig" {
 			// "--skip-*" flags or other whitelisted flags can be set with --config
 			return
 		}
@@ -328,3 +329,27 @@ func ValidateAPIEndpoint(c *kubeadm.MasterConfiguration, fldPath *field.Path) fi
 	}
 	return allErrs
 }
+
+// ValidateIgnoreChecksErrors validates duplicates in ignore-checks-errors flag.
+func ValidateIgnoreChecksErrors(ignoreChecksErrors []string, skipPreflightChecks bool) (sets.String, error) {
+	ignoreErrors := sets.NewString()
+	allErrs := field.ErrorList{}
+
+	for _, item := range ignoreChecksErrors {
+		ignoreErrors.Insert(strings.ToLower(item)) // parameters are case insensitive
+	}
+
+	// TODO: remove once deprecated flag --skip-preflight-checks is removed.
+	if skipPreflightChecks {
+		if ignoreErrors.Has("all") {
+			allErrs = append(allErrs, field.Invalid(field.NewPath("ignore-checks-errors"), strings.Join(ignoreErrors.List(), ","), "'all' is used together with deprecated flag --skip-preflight-checks. Remove deprecated flag"))
+		}
+		ignoreErrors.Insert("all")
+	}
+
+	if ignoreErrors.Has("all") && ignoreErrors.Len() > 1 {
+		allErrs = append(allErrs, field.Invalid(field.NewPath("ignore-checks-errors"), strings.Join(ignoreErrors.List(), ","), "don't specify individual checks if 'all' is used"))
+	}
+
+	return ignoreErrors, allErrs.ToAggregate()
+}
diff --git a/cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go b/cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go
index 2344c9a97f..ebc197eecb 100644
--- a/cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go
+++ b/cmd/kubeadm/app/apis/kubeadm/validation/validation_test.go
@@ -458,3 +458,32 @@ func TestValidateFeatureGates(t *testing.T) {
 		}
 	}
 }
+
+func TestValidateIgnoreChecksErrors(t *testing.T) {
+	var tests = []struct {
+		ignoreChecksErrors  []string
+		skipPreflightChecks bool
+		expectedLen         int
+		expectedError       bool
+	}{
+		{[]string{}, false, 0, false},                             // empty list, no old skip-preflight-checks
+		{[]string{}, true, 1, false},                              // empty list, old skip-preflight-checks
+		{[]string{"check1", "check2"}, false, 2, false},           // non-duplicate
+		{[]string{"check1", "check2"}, true, 3, true},             // non-duplicate, but skip-preflight-checks
+		{[]string{"check1", "check2", "check1"}, false, 2, false}, // duplicates
+		{[]string{"check1", "check2", "all"}, false, 3, true},     // non-duplicate, but 'all' present together wth individual checks
+		{[]string{"all"}, false, 1, false},                        // skip all checks by using new flag
+		{[]string{"all"}, true, 1, true},                          // skip all checks by using both old and new flags at the same time
+	}
+	for _, rt := range tests {
+		result, err := ValidateIgnoreChecksErrors(rt.ignoreChecksErrors, rt.skipPreflightChecks)
+		switch {
+		case err != nil && !rt.expectedError:
+			t.Errorf("ValidateIgnoreChecksErrors: unexpected error for input (%s, %v), error: %v", rt.ignoreChecksErrors, rt.skipPreflightChecks, err)
+		case err == nil && rt.expectedError:
+			t.Errorf("ValidateIgnoreChecksErrors: expected error for input (%s, %v) but got: %v", rt.ignoreChecksErrors, rt.skipPreflightChecks, result)
+		case result.Len() != rt.expectedLen:
+			t.Errorf("ValidateIgnoreChecksErrors: expected Len = %d for input (%s, %v) but got: %v, %v", rt.expectedLen, rt.ignoreChecksErrors, rt.skipPreflightChecks, result.Len(), result)
+		}
+	}
+}
diff --git a/cmd/kubeadm/app/cmd/init.go b/cmd/kubeadm/app/cmd/init.go
index 815a7ce81c..458e02f837 100644
--- a/cmd/kubeadm/app/cmd/init.go
+++ b/cmd/kubeadm/app/cmd/init.go
@@ -31,6 +31,7 @@ import (
 	flag "github.com/spf13/pflag"
 
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/sets"
 	clientset "k8s.io/client-go/kubernetes"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
@@ -112,6 +113,7 @@ func NewCmdInit(out io.Writer) *cobra.Command {
 	var dryRun bool
 	var featureGatesString string
 	var criSocket string
+	var ignoreChecksErrors []string
 
 	cmd := &cobra.Command{
 		Use:   "init",
@@ -126,7 +128,10 @@ func NewCmdInit(out io.Writer) *cobra.Command {
 			internalcfg := &kubeadmapi.MasterConfiguration{}
 			legacyscheme.Scheme.Convert(cfg, internalcfg, nil)
 
-			i, err := NewInit(cfgPath, internalcfg, skipPreFlight, skipTokenPrint, dryRun, criSocket)
+			ignoreChecksErrorsSet, err := validation.ValidateIgnoreChecksErrors(ignoreChecksErrors, skipPreFlight)
+			kubeadmutil.CheckErr(err)
+
+			i, err := NewInit(cfgPath, internalcfg, ignoreChecksErrorsSet, skipTokenPrint, dryRun, criSocket)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(i.Validate(cmd))
 			kubeadmutil.CheckErr(i.Run(out))
@@ -134,7 +139,7 @@ func NewCmdInit(out io.Writer) *cobra.Command {
 	}
 
 	AddInitConfigFlags(cmd.PersistentFlags(), cfg, &featureGatesString)
-	AddInitOtherFlags(cmd.PersistentFlags(), &cfgPath, &skipPreFlight, &skipTokenPrint, &dryRun, &criSocket)
+	AddInitOtherFlags(cmd.PersistentFlags(), &cfgPath, &skipPreFlight, &skipTokenPrint, &dryRun, &criSocket, &ignoreChecksErrors)
 
 	return cmd
 }
@@ -190,16 +195,21 @@ func AddInitConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiext.MasterConfigur
 }
 
 // AddInitOtherFlags adds init flags that are not bound to a configuration file to the given flagset
-func AddInitOtherFlags(flagSet *flag.FlagSet, cfgPath *string, skipPreFlight, skipTokenPrint, dryRun *bool, criSocket *string) {
+func AddInitOtherFlags(flagSet *flag.FlagSet, cfgPath *string, skipPreFlight, skipTokenPrint, dryRun *bool, criSocket *string, ignoreChecksErrors *[]string) {
 	flagSet.StringVar(
 		cfgPath, "config", *cfgPath,
 		"Path to kubeadm config file. WARNING: Usage of a configuration file is experimental.",
 	)
+	flagSet.StringSliceVar(
+		ignoreChecksErrors, "ignore-checks-errors", *ignoreChecksErrors,
+		"A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.",
+	)
 	// Note: All flags that are not bound to the cfg object should be whitelisted in cmd/kubeadm/app/apis/kubeadm/validation/validation.go
 	flagSet.BoolVar(
 		skipPreFlight, "skip-preflight-checks", *skipPreFlight,
 		"Skip preflight checks which normally run before modifying the system.",
 	)
+	flagSet.MarkDeprecated("skip-preflight-checks", "it is now equivalent to --ignore-checks-errors=all")
 	// Note: All flags that are not bound to the cfg object should be whitelisted in cmd/kubeadm/app/apis/kubeadm/validation/validation.go
 	flagSet.BoolVar(
 		skipTokenPrint, "skip-token-print", *skipTokenPrint,
@@ -217,7 +227,7 @@ func AddInitOtherFlags(flagSet *flag.FlagSet, cfgPath *string, skipPreFlight, sk
 }
 
 // NewInit validates given arguments and instantiates Init struct with provided information.
-func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight, skipTokenPrint, dryRun bool, criSocket string) (*Init, error) {
+func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, ignoreChecksErrors sets.String, skipTokenPrint, dryRun bool, criSocket string) (*Init, error) {
 	fmt.Println("[kubeadm] WARNING: kubeadm is currently in beta")
 
 	if cfgPath != "" {
@@ -249,19 +259,15 @@ func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight,
 		fmt.Println("\t(/etc/systemd/system/kubelet.service.d/10-kubeadm.conf should be edited for this purpose)")
 	}
 
-	if !skipPreFlight {
-		fmt.Println("[preflight] Running pre-flight checks.")
+	fmt.Println("[preflight] Running pre-flight checks.")
 
-		if err := preflight.RunInitMasterChecks(utilsexec.New(), cfg, criSocket); err != nil {
-			return nil, err
-		}
-
-		// Try to start the kubelet service in case it's inactive
-		preflight.TryStartKubelet()
-	} else {
-		fmt.Println("[preflight] Skipping pre-flight checks.")
+	if err := preflight.RunInitMasterChecks(utilsexec.New(), cfg, criSocket, ignoreChecksErrors); err != nil {
+		return nil, err
 	}
 
+	// Try to start the kubelet service in case it's inactive
+	preflight.TryStartKubelet(ignoreChecksErrors)
+
 	return &Init{cfg: cfg, skipTokenPrint: skipTokenPrint, dryRun: dryRun}, nil
 }
 
diff --git a/cmd/kubeadm/app/cmd/join.go b/cmd/kubeadm/app/cmd/join.go
index 266f268b06..9b34fc0846 100644
--- a/cmd/kubeadm/app/cmd/join.go
+++ b/cmd/kubeadm/app/cmd/join.go
@@ -29,6 +29,7 @@ import (
 	flag "github.com/spf13/pflag"
 
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/apimachinery/pkg/util/wait"
 	clientset "k8s.io/client-go/kubernetes"
 	certutil "k8s.io/client-go/util/cert"
@@ -110,6 +111,7 @@ func NewCmdJoin(out io.Writer) *cobra.Command {
 	var cfgPath string
 	var criSocket string
 	var featureGatesString string
+	var ignoreChecksErrors []string
 
 	cmd := &cobra.Command{
 		Use:   "join [flags]",
@@ -127,7 +129,10 @@ func NewCmdJoin(out io.Writer) *cobra.Command {
 			internalcfg := &kubeadmapi.NodeConfiguration{}
 			legacyscheme.Scheme.Convert(cfg, internalcfg, nil)
 
-			j, err := NewJoin(cfgPath, args, internalcfg, skipPreFlight, criSocket)
+			ignoreChecksErrorsSet, err := validation.ValidateIgnoreChecksErrors(ignoreChecksErrors, skipPreFlight)
+			kubeadmutil.CheckErr(err)
+
+			j, err := NewJoin(cfgPath, args, internalcfg, ignoreChecksErrorsSet, criSocket)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(j.Validate(cmd))
 			kubeadmutil.CheckErr(j.Run(out))
@@ -135,7 +140,7 @@ func NewCmdJoin(out io.Writer) *cobra.Command {
 	}
 
 	AddJoinConfigFlags(cmd.PersistentFlags(), cfg, &featureGatesString)
-	AddJoinOtherFlags(cmd.PersistentFlags(), &cfgPath, &skipPreFlight, &criSocket)
+	AddJoinOtherFlags(cmd.PersistentFlags(), &cfgPath, &skipPreFlight, &criSocket, &ignoreChecksErrors)
 
 	return cmd
 }
@@ -170,15 +175,20 @@ func AddJoinConfigFlags(flagSet *flag.FlagSet, cfg *kubeadmapiext.NodeConfigurat
 }
 
 // AddJoinOtherFlags adds join flags that are not bound to a configuration file to the given flagset
-func AddJoinOtherFlags(flagSet *flag.FlagSet, cfgPath *string, skipPreFlight *bool, criSocket *string) {
+func AddJoinOtherFlags(flagSet *flag.FlagSet, cfgPath *string, skipPreFlight *bool, criSocket *string, ignoreChecksErrors *[]string) {
 	flagSet.StringVar(
 		cfgPath, "config", *cfgPath,
 		"Path to kubeadm config file.")
 
+	flagSet.StringSliceVar(
+		ignoreChecksErrors, "ignore-checks-errors", *ignoreChecksErrors,
+		"A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.",
+	)
 	flagSet.BoolVar(
 		skipPreFlight, "skip-preflight-checks", false,
 		"Skip preflight checks which normally run before modifying the system.",
 	)
+	flagSet.MarkDeprecated("skip-preflight-checks", "it is now equivalent to --ignore-checks-errors=all")
 	flagSet.StringVar(
 		criSocket, "cri-socket", "/var/run/dockershim.sock",
 		`Specify the CRI socket to connect to.`,
@@ -191,7 +201,7 @@ type Join struct {
 }
 
 // NewJoin instantiates Join struct with given arguments
-func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, skipPreFlight bool, criSocket string) (*Join, error) {
+func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, ignoreChecksErrors sets.String, criSocket string) (*Join, error) {
 	fmt.Println("[kubeadm] WARNING: kubeadm is currently in beta")
 
 	if cfg.NodeName == "" {
@@ -208,20 +218,16 @@ func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, s
 		}
 	}
 
-	if !skipPreFlight {
-		fmt.Println("[preflight] Running pre-flight checks.")
+	fmt.Println("[preflight] Running pre-flight checks.")
 
-		// Then continue with the others...
-		if err := preflight.RunJoinNodeChecks(utilsexec.New(), cfg, criSocket); err != nil {
-			return nil, err
-		}
-
-		// Try to start the kubelet service in case it's inactive
-		preflight.TryStartKubelet()
-	} else {
-		fmt.Println("[preflight] Skipping pre-flight checks.")
+	// Then continue with the others...
+	if err := preflight.RunJoinNodeChecks(utilsexec.New(), cfg, criSocket, ignoreChecksErrors); err != nil {
+		return nil, err
 	}
 
+	// Try to start the kubelet service in case it's inactive
+	preflight.TryStartKubelet(ignoreChecksErrors)
+
 	return &Join{cfg: cfg}, nil
 }
 
diff --git a/cmd/kubeadm/app/cmd/phases/BUILD b/cmd/kubeadm/app/cmd/phases/BUILD
index d4cc7c6301..e2b0c0049e 100644
--- a/cmd/kubeadm/app/cmd/phases/BUILD
+++ b/cmd/kubeadm/app/cmd/phases/BUILD
@@ -50,6 +50,7 @@ go_library(
         "//pkg/util/normalizer:go_default_library",
         "//vendor/github.com/spf13/cobra:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/client-go/kubernetes:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",
     ],
diff --git a/cmd/kubeadm/app/cmd/phases/preflight.go b/cmd/kubeadm/app/cmd/phases/preflight.go
index 9e91da3ae0..54b51343af 100644
--- a/cmd/kubeadm/app/cmd/phases/preflight.go
+++ b/cmd/kubeadm/app/cmd/phases/preflight.go
@@ -19,6 +19,7 @@ package phases
 import (
 	"github.com/spf13/cobra"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/preflight"
@@ -70,7 +71,7 @@ func NewCmdPreFlightMaster() *cobra.Command {
 		Run: func(cmd *cobra.Command, args []string) {
 			cfg := &kubeadmapi.MasterConfiguration{}
 			criSocket := ""
-			err := preflight.RunInitMasterChecks(utilsexec.New(), cfg, criSocket)
+			err := preflight.RunInitMasterChecks(utilsexec.New(), cfg, criSocket, sets.NewString())
 			kubeadmutil.CheckErr(err)
 		},
 	}
@@ -88,7 +89,7 @@ func NewCmdPreFlightNode() *cobra.Command {
 		Run: func(cmd *cobra.Command, args []string) {
 			cfg := &kubeadmapi.NodeConfiguration{}
 			criSocket := ""
-			err := preflight.RunJoinNodeChecks(utilsexec.New(), cfg, criSocket)
+			err := preflight.RunJoinNodeChecks(utilsexec.New(), cfg, criSocket, sets.NewString())
 			kubeadmutil.CheckErr(err)
 		},
 	}
diff --git a/cmd/kubeadm/app/cmd/reset.go b/cmd/kubeadm/app/cmd/reset.go
index 74db95f0e4..0352f6fd1b 100644
--- a/cmd/kubeadm/app/cmd/reset.go
+++ b/cmd/kubeadm/app/cmd/reset.go
@@ -26,7 +26,9 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
+	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	kubeadmconstants "k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/preflight"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
@@ -45,20 +47,30 @@ func NewCmdReset(out io.Writer) *cobra.Command {
 	var skipPreFlight bool
 	var certsDir string
 	var criSocketPath string
+	var ignoreChecksErrors []string
+
 	cmd := &cobra.Command{
 		Use:   "reset",
 		Short: "Run this to revert any changes made to this host by 'kubeadm init' or 'kubeadm join'.",
 		Run: func(cmd *cobra.Command, args []string) {
-			r, err := NewReset(skipPreFlight, certsDir, criSocketPath)
+			ignoreChecksErrorsSet, err := validation.ValidateIgnoreChecksErrors(ignoreChecksErrors, skipPreFlight)
+			kubeadmutil.CheckErr(err)
+
+			r, err := NewReset(ignoreChecksErrorsSet, certsDir, criSocketPath)
 			kubeadmutil.CheckErr(err)
 			kubeadmutil.CheckErr(r.Run(out))
 		},
 	}
 
+	cmd.PersistentFlags().StringSliceVar(
+		&ignoreChecksErrors, "ignore-checks-errors", ignoreChecksErrors,
+		"A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.",
+	)
 	cmd.PersistentFlags().BoolVar(
 		&skipPreFlight, "skip-preflight-checks", false,
 		"Skip preflight checks which normally run before modifying the system.",
 	)
+	cmd.PersistentFlags().MarkDeprecated("skip-preflight-checks", "it is now equivalent to --ignore-checks-errors=all")
 
 	cmd.PersistentFlags().StringVar(
 		&certsDir, "cert-dir", kubeadmapiext.DefaultCertificatesDir,
@@ -80,15 +92,11 @@ type Reset struct {
 }
 
 // NewReset instantiate Reset struct
-func NewReset(skipPreFlight bool, certsDir, criSocketPath string) (*Reset, error) {
-	if !skipPreFlight {
-		fmt.Println("[preflight] Running pre-flight checks.")
+func NewReset(ignoreChecksErrors sets.String, certsDir, criSocketPath string) (*Reset, error) {
+	fmt.Println("[preflight] Running pre-flight checks.")
 
-		if err := preflight.RunRootCheckOnly(); err != nil {
-			return nil, err
-		}
-	} else {
-		fmt.Println("[preflight] Skipping pre-flight checks.")
+	if err := preflight.RunRootCheckOnly(ignoreChecksErrors); err != nil {
+		return nil, err
 	}
 
 	return &Reset{
diff --git a/cmd/kubeadm/app/cmd/reset_test.go b/cmd/kubeadm/app/cmd/reset_test.go
index 08a26328d6..59780e0a5a 100644
--- a/cmd/kubeadm/app/cmd/reset_test.go
+++ b/cmd/kubeadm/app/cmd/reset_test.go
@@ -195,6 +195,10 @@ func (c *fakeDockerChecker) Check() (warnings, errors []error) {
 	return c.warnings, c.errors
 }
 
+func (c *fakeDockerChecker) Name() string {
+	return "FakeDocker"
+}
+
 func newFakeDockerChecker(warnings, errors []error) preflight.Checker {
 	return &fakeDockerChecker{warnings: warnings, errors: errors}
 }
diff --git a/cmd/kubeadm/app/cmd/upgrade/BUILD b/cmd/kubeadm/app/cmd/upgrade/BUILD
index e0489bd934..28658102d5 100644
--- a/cmd/kubeadm/app/cmd/upgrade/BUILD
+++ b/cmd/kubeadm/app/cmd/upgrade/BUILD
@@ -13,6 +13,7 @@ go_library(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//cmd/kubeadm/app/apis/kubeadm/v1alpha1:go_default_library",
+        "//cmd/kubeadm/app/apis/kubeadm/validation:go_default_library",
         "//cmd/kubeadm/app/cmd/util:go_default_library",
         "//cmd/kubeadm/app/constants:go_default_library",
         "//cmd/kubeadm/app/phases/controlplane:go_default_library",
@@ -27,6 +28,7 @@ go_library(
         "//pkg/util/version:go_default_library",
         "//vendor/github.com/ghodss/yaml:go_default_library",
         "//vendor/github.com/spf13/cobra:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/client-go/discovery/fake:go_default_library",
         "//vendor/k8s.io/client-go/kubernetes:go_default_library",
     ],
diff --git a/cmd/kubeadm/app/cmd/upgrade/apply.go b/cmd/kubeadm/app/cmd/upgrade/apply.go
index b36ddf23c1..9df0c51b7a 100644
--- a/cmd/kubeadm/app/cmd/upgrade/apply.go
+++ b/cmd/kubeadm/app/cmd/upgrade/apply.go
@@ -25,6 +25,7 @@ import (
 
 	clientset "k8s.io/client-go/kubernetes"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
+	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 	"k8s.io/kubernetes/cmd/kubeadm/app/constants"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/controlplane"
@@ -70,8 +71,12 @@ func NewCmdApply(parentFlags *cmdUpgradeFlags) *cobra.Command {
 		Use:   "apply [version]",
 		Short: "Upgrade your Kubernetes cluster to the specified version.",
 		Run: func(cmd *cobra.Command, args []string) {
+			var err error
+			flags.parent.ignoreChecksErrorsSet, err = validation.ValidateIgnoreChecksErrors(flags.parent.ignoreChecksErrors, flags.parent.skipPreFlight)
+			kubeadmutil.CheckErr(err)
+
 			// Ensure the user is root
-			err := runPreflightChecks(flags.parent.skipPreFlight)
+			err = runPreflightChecks(flags.parent.ignoreChecksErrorsSet)
 			kubeadmutil.CheckErr(err)
 
 			err = cmdutil.ValidateExactArgNumber(args, []string{"version"})
diff --git a/cmd/kubeadm/app/cmd/upgrade/common.go b/cmd/kubeadm/app/cmd/upgrade/common.go
index fdbe23a1e6..00e1fa031d 100644
--- a/cmd/kubeadm/app/cmd/upgrade/common.go
+++ b/cmd/kubeadm/app/cmd/upgrade/common.go
@@ -26,6 +26,7 @@ import (
 
 	"github.com/ghodss/yaml"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	fakediscovery "k8s.io/client-go/discovery/fake"
 	clientset "k8s.io/client-go/kubernetes"
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
@@ -97,14 +98,9 @@ func printConfiguration(cfg *kubeadmapiext.MasterConfiguration, w io.Writer) {
 }
 
 // runPreflightChecks runs the root preflight check
-func runPreflightChecks(skipPreFlight bool) error {
-	if skipPreFlight {
-		fmt.Println("[preflight] Skipping pre-flight checks.")
-		return nil
-	}
-
+func runPreflightChecks(ignoreChecksErrors sets.String) error {
 	fmt.Println("[preflight] Running pre-flight checks.")
-	return preflight.RunRootCheckOnly()
+	return preflight.RunRootCheckOnly(ignoreChecksErrors)
 }
 
 // getClient gets a real or fake client depending on whether the user is dry-running or not
diff --git a/cmd/kubeadm/app/cmd/upgrade/plan.go b/cmd/kubeadm/app/cmd/upgrade/plan.go
index 43b74d5174..e09c70c1be 100644
--- a/cmd/kubeadm/app/cmd/upgrade/plan.go
+++ b/cmd/kubeadm/app/cmd/upgrade/plan.go
@@ -25,6 +25,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/upgrade"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
 )
@@ -35,8 +36,11 @@ func NewCmdPlan(parentFlags *cmdUpgradeFlags) *cobra.Command {
 		Use:   "plan",
 		Short: "Check which versions are available to upgrade to and validate whether your current cluster is upgradeable.",
 		Run: func(_ *cobra.Command, _ []string) {
+			var err error
+			parentFlags.ignoreChecksErrorsSet, err = validation.ValidateIgnoreChecksErrors(parentFlags.ignoreChecksErrors, parentFlags.skipPreFlight)
+			kubeadmutil.CheckErr(err)
 			// Ensure the user is root
-			err := runPreflightChecks(parentFlags.skipPreFlight)
+			err = runPreflightChecks(parentFlags.ignoreChecksErrorsSet)
 			kubeadmutil.CheckErr(err)
 
 			err = RunPlan(parentFlags)
diff --git a/cmd/kubeadm/app/cmd/upgrade/upgrade.go b/cmd/kubeadm/app/cmd/upgrade/upgrade.go
index d5d1f97107..0be0ef1254 100644
--- a/cmd/kubeadm/app/cmd/upgrade/upgrade.go
+++ b/cmd/kubeadm/app/cmd/upgrade/upgrade.go
@@ -20,6 +20,7 @@ import (
 	"io"
 
 	"github.com/spf13/cobra"
+	"k8s.io/apimachinery/pkg/util/sets"
 	cmdutil "k8s.io/kubernetes/cmd/kubeadm/app/cmd/util"
 )
 
@@ -31,6 +32,8 @@ type cmdUpgradeFlags struct {
 	allowRCUpgrades           bool
 	printConfig               bool
 	skipPreFlight             bool
+	ignoreChecksErrors        []string
+	ignoreChecksErrorsSet     sets.String
 }
 
 // NewCmdUpgrade returns the cobra command for `kubeadm upgrade`
@@ -42,6 +45,7 @@ func NewCmdUpgrade(out io.Writer) *cobra.Command {
 		allowRCUpgrades:           false,
 		printConfig:               false,
 		skipPreFlight:             false,
+		ignoreChecksErrorsSet:     sets.NewString(),
 	}
 
 	cmd := &cobra.Command{
@@ -55,7 +59,9 @@ func NewCmdUpgrade(out io.Writer) *cobra.Command {
 	cmd.PersistentFlags().BoolVar(&flags.allowExperimentalUpgrades, "allow-experimental-upgrades", flags.allowExperimentalUpgrades, "Show unstable versions of Kubernetes as an upgrade alternative and allow upgrading to an alpha/beta/release candidate versions of Kubernetes.")
 	cmd.PersistentFlags().BoolVar(&flags.allowRCUpgrades, "allow-release-candidate-upgrades", flags.allowRCUpgrades, "Show release candidate versions of Kubernetes as an upgrade alternative and allow upgrading to a release candidate versions of Kubernetes.")
 	cmd.PersistentFlags().BoolVar(&flags.printConfig, "print-config", flags.printConfig, "Specifies whether the configuration file that will be used in the upgrade should be printed or not.")
+	cmd.PersistentFlags().StringSliceVar(&flags.ignoreChecksErrors, "ignore-checks-errors", flags.ignoreChecksErrors, "A list of checks whose errors will be shown as warnings. Example: 'IsPrivilegedUser,Swap'. Value 'all' ignores errors from all checks.")
 	cmd.PersistentFlags().BoolVar(&flags.skipPreFlight, "skip-preflight-checks", flags.skipPreFlight, "Skip preflight checks that normally run before modifying the system.")
+	cmd.PersistentFlags().MarkDeprecated("skip-preflight-checks", "it is now equivalent to --ignore-checks-errors=all")
 
 	cmd.AddCommand(NewCmdApply(flags))
 	cmd.AddCommand(NewCmdPlan(flags))
diff --git a/cmd/kubeadm/app/preflight/BUILD b/cmd/kubeadm/app/preflight/BUILD
index 09382e316c..baaea43aa3 100644
--- a/cmd/kubeadm/app/preflight/BUILD
+++ b/cmd/kubeadm/app/preflight/BUILD
@@ -36,6 +36,7 @@ go_library(
         "//vendor/github.com/blang/semver:go_default_library",
         "//vendor/github.com/spf13/pflag:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/util/net:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",
     ],
 )
@@ -51,6 +52,7 @@ go_test(
     deps = [
         "//cmd/kubeadm/app/apis/kubeadm:go_default_library",
         "//vendor/github.com/renstrom/dedent:go_default_library",
+        "//vendor/k8s.io/apimachinery/pkg/util/sets:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",
     ],
 )
diff --git a/cmd/kubeadm/app/preflight/checks.go b/cmd/kubeadm/app/preflight/checks.go
index 2efef91378..f36b2e066c 100644
--- a/cmd/kubeadm/app/preflight/checks.go
+++ b/cmd/kubeadm/app/preflight/checks.go
@@ -41,6 +41,7 @@ import (
 	"net/url"
 
 	netutil "k8s.io/apimachinery/pkg/util/net"
+	"k8s.io/apimachinery/pkg/util/sets"
 	apiservoptions "k8s.io/kubernetes/cmd/kube-apiserver/app/options"
 	cmoptions "k8s.io/kubernetes/cmd/kube-controller-manager/app/options"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
@@ -74,13 +75,14 @@ type Error struct {
 }
 
 func (e *Error) Error() string {
-	return fmt.Sprintf("[preflight] Some fatal errors occurred:\n%s%s", e.Msg, "[preflight] If you know what you are doing, you can skip pre-flight checks with `--skip-preflight-checks`")
+	return fmt.Sprintf("[preflight] Some fatal errors occurred:\n%s%s", e.Msg, "[preflight] If you know what you are doing, you can make a check non-fatal with `--ignore-checks-errors=...`")
 }
 
 // Checker validates the state of the system to ensure kubeadm will be
 // successful as often as possilble.
 type Checker interface {
 	Check() (warnings, errors []error)
+	Name() string
 }
 
 // CRICheck verifies the container runtime through the CRI.
@@ -89,6 +91,11 @@ type CRICheck struct {
 	exec   utilsexec.Interface
 }
 
+// Name returns label for CRICheck.
+func (CRICheck) Name() string {
+	return "CRI"
+}
+
 // Check validates the container runtime through the CRI.
 func (criCheck CRICheck) Check() (warnings, errors []error) {
 	if err := criCheck.exec.Command("sh", "-c", fmt.Sprintf("crictl -r %s info", criCheck.socket)).Run(); err != nil {
@@ -104,6 +111,15 @@ func (criCheck CRICheck) Check() (warnings, errors []error) {
 type ServiceCheck struct {
 	Service       string
 	CheckIfActive bool
+	Label         string
+}
+
+// Name returns label for ServiceCheck. If not provided, will return based on the service parameter
+func (sc ServiceCheck) Name() string {
+	if sc.Label != "" {
+		return sc.Label
+	}
+	return fmt.Sprintf("Service-%s", strings.Title(sc.Service))
 }
 
 // Check validates if the service is enabled and active.
@@ -141,6 +157,11 @@ type FirewalldCheck struct {
 	ports []int
 }
 
+// Name returns label for FirewalldCheck.
+func (FirewalldCheck) Name() string {
+	return "Firewalld"
+}
+
 // Check validates if the firewall is enabled and active.
 func (fc FirewalldCheck) Check() (warnings, errors []error) {
 	initSystem, err := initsystem.GetInitSystem()
@@ -165,7 +186,16 @@ func (fc FirewalldCheck) Check() (warnings, errors []error) {
 
 // PortOpenCheck ensures the given port is available for use.
 type PortOpenCheck struct {
-	port int
+	port  int
+	label string
+}
+
+// Name returns name for PortOpenCheck. If not known, will return "PortXXXX" based on port number
+func (poc PortOpenCheck) Name() string {
+	if poc.label != "" {
+		return poc.label
+	}
+	return fmt.Sprintf("Port-%d", poc.port)
 }
 
 // Check validates if the particular port is available.
@@ -185,9 +215,23 @@ func (poc PortOpenCheck) Check() (warnings, errors []error) {
 // IsPrivilegedUserCheck verifies user is privileged (linux - root, windows - Administrator)
 type IsPrivilegedUserCheck struct{}
 
+// Name returns name for IsPrivilegedUserCheck
+func (IsPrivilegedUserCheck) Name() string {
+	return "IsPrivilegedUser"
+}
+
 // DirAvailableCheck checks if the given directory either does not exist, or is empty.
 type DirAvailableCheck struct {
-	Path string
+	Path  string
+	Label string
+}
+
+// Name returns label for individual DirAvailableChecks. If not known, will return based on path.
+func (dac DirAvailableCheck) Name() string {
+	if dac.Label != "" {
+		return dac.Label
+	}
+	return fmt.Sprintf("DirAvailable-%s", strings.Replace(dac.Path, "/", "-", -1))
 }
 
 // Check validates if a directory does not exist or empty.
@@ -215,7 +259,16 @@ func (dac DirAvailableCheck) Check() (warnings, errors []error) {
 
 // FileAvailableCheck checks that the given file does not already exist.
 type FileAvailableCheck struct {
-	Path string
+	Path  string
+	Label string
+}
+
+// Name returns label for individual FileAvailableChecks. If not known, will return based on path.
+func (fac FileAvailableCheck) Name() string {
+	if fac.Label != "" {
+		return fac.Label
+	}
+	return fmt.Sprintf("FileAvailable-%s", strings.Replace(fac.Path, "/", "-", -1))
 }
 
 // Check validates if the given file does not already exist.
@@ -229,7 +282,16 @@ func (fac FileAvailableCheck) Check() (warnings, errors []error) {
 
 // FileExistingCheck checks that the given file does not already exist.
 type FileExistingCheck struct {
-	Path string
+	Path  string
+	Label string
+}
+
+// Name returns label for individual FileExistingChecks. If not known, will return based on path.
+func (fac FileExistingCheck) Name() string {
+	if fac.Label != "" {
+		return fac.Label
+	}
+	return fmt.Sprintf("FileExisting-%s", strings.Replace(fac.Path, "/", "-", -1))
 }
 
 // Check validates if the given file already exists.
@@ -245,6 +307,15 @@ func (fac FileExistingCheck) Check() (warnings, errors []error) {
 type FileContentCheck struct {
 	Path    string
 	Content []byte
+	Label   string
+}
+
+// Name returns label for individual FileContentChecks. If not known, will return based on path.
+func (fcc FileContentCheck) Name() string {
+	if fcc.Label != "" {
+		return fcc.Label
+	}
+	return fmt.Sprintf("FileContent-%s", strings.Replace(fcc.Path, "/", "-", -1))
 }
 
 // Check validates if the given file contains the given content.
@@ -275,6 +346,15 @@ type InPathCheck struct {
 	executable string
 	mandatory  bool
 	exec       utilsexec.Interface
+	label      string
+}
+
+// Name returns label for individual InPathCheck. If not known, will return based on path.
+func (ipc InPathCheck) Name() string {
+	if ipc.label != "" {
+		return ipc.label
+	}
+	return fmt.Sprintf("FileExisting-%s", strings.Replace(ipc.executable, "/", "-", -1))
 }
 
 // Check validates if the given executable is present in the path.
@@ -297,6 +377,11 @@ type HostnameCheck struct {
 	nodeName string
 }
 
+// Name will return Hostname as name for HostnameCheck
+func (HostnameCheck) Name() string {
+	return "Hostname"
+}
+
 // Check validates if hostname match dns sub domain regex.
 func (hc HostnameCheck) Check() (warnings, errors []error) {
 	errors = []error{}
@@ -322,6 +407,11 @@ type HTTPProxyCheck struct {
 	Port  int
 }
 
+// Name returns HTTPProxy as name for HTTPProxyCheck
+func (hst HTTPProxyCheck) Name() string {
+	return "HTTPProxy"
+}
+
 // Check validates http connectivity type, direct or via proxy.
 func (hst HTTPProxyCheck) Check() (warnings, errors []error) {
 
@@ -352,6 +442,11 @@ type HTTPProxyCIDRCheck struct {
 	CIDR  string
 }
 
+// Name will return HTTPProxyCIDR as name for HTTPProxyCIDRCheck
+func (HTTPProxyCIDRCheck) Name() string {
+	return "HTTPProxyCIDR"
+}
+
 // Check validates http connectivity to first IP address in the CIDR.
 // If it is not directly connected and goes via proxy it will produce warning.
 func (subnet HTTPProxyCIDRCheck) Check() (warnings, errors []error) {
@@ -399,6 +494,11 @@ type ExtraArgsCheck struct {
 	SchedulerExtraArgs         map[string]string
 }
 
+// Name will return ExtraArgs as name for ExtraArgsCheck
+func (ExtraArgsCheck) Name() string {
+	return "ExtraArgs"
+}
+
 // Check validates additional arguments of the control plane components.
 func (eac ExtraArgsCheck) Check() (warnings, errors []error) {
 	argsCheck := func(name string, args map[string]string, f *pflag.FlagSet) []error {
@@ -438,6 +538,11 @@ type SystemVerificationCheck struct {
 	CRISocket string
 }
 
+// Name will return SystemVerification as name for SystemVerificationCheck
+func (SystemVerificationCheck) Name() string {
+	return "SystemVerification"
+}
+
 // Check runs all individual checks
 func (sysver SystemVerificationCheck) Check() (warnings, errors []error) {
 	// Create a buffered writer and choose a quite large value (1M) and suppose the output from the system verification test won't exceed the limit
@@ -490,6 +595,11 @@ type KubernetesVersionCheck struct {
 	KubernetesVersion string
 }
 
+// Name will return KubernetesVersion as name for KubernetesVersionCheck
+func (KubernetesVersionCheck) Name() string {
+	return "KubernetesVersion"
+}
+
 // Check validates kubernetes and kubeadm versions
 func (kubever KubernetesVersionCheck) Check() (warnings, errors []error) {
 
@@ -525,6 +635,11 @@ type KubeletVersionCheck struct {
 	KubernetesVersion string
 }
 
+// Name will return KubeletVersion as name for KubeletVersionCheck
+func (KubeletVersionCheck) Name() string {
+	return "KubeletVersion"
+}
+
 // Check validates kubelet version. It should be not less than minimal supported version
 func (kubever KubeletVersionCheck) Check() (warnings, errors []error) {
 	kubeletVersion, err := GetKubeletVersion()
@@ -550,6 +665,11 @@ func (kubever KubeletVersionCheck) Check() (warnings, errors []error) {
 // SwapCheck warns if swap is enabled
 type SwapCheck struct{}
 
+// Name will return Swap as name for SwapCheck
+func (SwapCheck) Name() string {
+	return "Swap"
+}
+
 // Check validates whether swap is enabled or not
 func (swc SwapCheck) Check() (warnings, errors []error) {
 	f, err := os.Open("/proc/swaps")
@@ -584,6 +704,11 @@ type ExternalEtcdVersionCheck struct {
 	Etcd kubeadmapi.Etcd
 }
 
+// Name will return ExternalEtcdVersion as name for ExternalEtcdVersionCheck
+func (ExternalEtcdVersionCheck) Name() string {
+	return "ExternalEtcdVersion"
+}
+
 // Check validates external etcd version
 func (evc ExternalEtcdVersionCheck) Check() (warnings, errors []error) {
 	var config *tls.Config
@@ -712,9 +837,9 @@ func getEtcdVersionResponse(client *http.Client, url string, target interface{})
 }
 
 // RunInitMasterChecks executes all individual, applicable to Master node checks.
-func RunInitMasterChecks(execer utilsexec.Interface, cfg *kubeadmapi.MasterConfiguration, criSocket string) error {
+func RunInitMasterChecks(execer utilsexec.Interface, cfg *kubeadmapi.MasterConfiguration, criSocket string, ignoreChecksErrors sets.String) error {
 	// First, check if we're root separately from the other preflight checks and fail fast
-	if err := RunRootCheckOnly(); err != nil {
+	if err := RunRootCheckOnly(ignoreChecksErrors); err != nil {
 		return err
 	}
 
@@ -804,13 +929,13 @@ func RunInitMasterChecks(execer utilsexec.Interface, cfg *kubeadmapi.MasterConfi
 			)
 		}
 	}
-	return RunChecks(checks, os.Stderr)
+	return RunChecks(checks, os.Stderr, ignoreChecksErrors)
 }
 
 // RunJoinNodeChecks executes all individual, applicable to node checks.
-func RunJoinNodeChecks(execer utilsexec.Interface, cfg *kubeadmapi.NodeConfiguration, criSocket string) error {
+func RunJoinNodeChecks(execer utilsexec.Interface, cfg *kubeadmapi.NodeConfiguration, criSocket string, ignoreChecksErrors sets.String) error {
 	// First, check if we're root separately from the other preflight checks and fail fast
-	if err := RunRootCheckOnly(); err != nil {
+	if err := RunRootCheckOnly(ignoreChecksErrors); err != nil {
 		return err
 	}
 
@@ -862,33 +987,50 @@ func RunJoinNodeChecks(execer utilsexec.Interface, cfg *kubeadmapi.NodeConfigura
 			}
 		}
 	}
-	return RunChecks(checks, os.Stderr)
+	return RunChecks(checks, os.Stderr, ignoreChecksErrors)
 }
 
 // RunRootCheckOnly initializes checks slice of structs and call RunChecks
-func RunRootCheckOnly() error {
+func RunRootCheckOnly(ignoreChecksErrors sets.String) error {
 	checks := []Checker{
 		IsPrivilegedUserCheck{},
 	}
 
-	return RunChecks(checks, os.Stderr)
+	return RunChecks(checks, os.Stderr, ignoreChecksErrors)
 }
 
 // RunChecks runs each check, displays it's warnings/errors, and once all
 // are processed will exit if any errors occurred.
-func RunChecks(checks []Checker, ww io.Writer) error {
-	found := []error{}
+func RunChecks(checks []Checker, ww io.Writer, ignoreChecksErrors sets.String) error {
+	type checkErrors struct {
+		Name   string
+		Errors []error
+	}
+	found := []checkErrors{}
+
 	for _, c := range checks {
+		name := c.Name()
 		warnings, errs := c.Check()
-		for _, w := range warnings {
-			io.WriteString(ww, fmt.Sprintf("[preflight] WARNING: %v\n", w))
+
+		if setHasItemOrAll(ignoreChecksErrors, name) {
+			// Decrease severity of errors to warnings for this check
+			warnings = append(warnings, errs...)
+			errs = []error{}
+		}
+
+		for _, w := range warnings {
+			io.WriteString(ww, fmt.Sprintf("\t[WARNING %s]: %v\n", name, w))
+		}
+		if len(errs) > 0 {
+			found = append(found, checkErrors{Name: name, Errors: errs})
 		}
-		found = append(found, errs...)
 	}
 	if len(found) > 0 {
 		var errs bytes.Buffer
-		for _, i := range found {
-			errs.WriteString("\t" + i.Error() + "\n")
+		for _, c := range found {
+			for _, i := range c.Errors {
+				errs.WriteString(fmt.Sprintf("\t[ERROR %s]: %v\n", c.Name, i.Error()))
+			}
 		}
 		return &Error{Msg: errs.String()}
 	}
@@ -896,7 +1038,10 @@ func RunChecks(checks []Checker, ww io.Writer) error {
 }
 
 // TryStartKubelet attempts to bring up kubelet service
-func TryStartKubelet() {
+func TryStartKubelet(ignoreChecksErrors sets.String) {
+	if setHasItemOrAll(ignoreChecksErrors, "StartKubelet") {
+		return
+	}
 	// If we notice that the kubelet service is inactive, try to start it
 	initSystem, err := initsystem.GetInitSystem()
 	if err != nil {
@@ -910,3 +1055,11 @@ func TryStartKubelet() {
 		}
 	}
 }
+
+// setHasItemOrAll is helper function that return true if item is present in the set (case insensitive) or special key 'all' is present
+func setHasItemOrAll(s sets.String, item string) bool {
+	if s.Has("all") || s.Has(strings.ToLower(item)) {
+		return true
+	}
+	return false
+}
diff --git a/cmd/kubeadm/app/preflight/checks_test.go b/cmd/kubeadm/app/preflight/checks_test.go
index f2703a0da2..2432b7c2ce 100644
--- a/cmd/kubeadm/app/preflight/checks_test.go
+++ b/cmd/kubeadm/app/preflight/checks_test.go
@@ -29,6 +29,7 @@ import (
 	"net/http"
 	"os"
 
+	"k8s.io/apimachinery/pkg/util/sets"
 	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	"k8s.io/utils/exec"
 )
@@ -166,6 +167,10 @@ type preflightCheckTest struct {
 	msg string
 }
 
+func (pfct preflightCheckTest) Name() string {
+	return "preflightCheckTest"
+}
+
 func (pfct preflightCheckTest) Check() (warning, errors []error) {
 	if pfct.msg == "warning" {
 		return []error{fmt.Errorf("warning")}, nil
@@ -218,7 +223,7 @@ func TestRunInitMasterChecks(t *testing.T) {
 	}
 
 	for _, rt := range tests {
-		actual := RunInitMasterChecks(exec.New(), rt.cfg, "")
+		actual := RunInitMasterChecks(exec.New(), rt.cfg, "", sets.NewString())
 		if (actual == nil) != rt.expected {
 			t.Errorf(
 				"failed RunInitMasterChecks:\n\texpected: %t\n\t  actual: %t\n\t error: %v",
@@ -254,7 +259,7 @@ func TestRunJoinNodeChecks(t *testing.T) {
 	}
 
 	for _, rt := range tests {
-		actual := RunJoinNodeChecks(exec.New(), rt.cfg, "")
+		actual := RunJoinNodeChecks(exec.New(), rt.cfg, "", sets.NewString())
 		if (actual == nil) != rt.expected {
 			t.Errorf(
 				"failed RunJoinNodeChecks:\n\texpected: %t\n\t  actual: %t",
@@ -272,7 +277,7 @@ func TestRunChecks(t *testing.T) {
 		output   string
 	}{
 		{[]Checker{}, true, ""},
-		{[]Checker{preflightCheckTest{"warning"}}, true, "[preflight] WARNING: warning\n"}, // should just print warning
+		{[]Checker{preflightCheckTest{"warning"}}, true, "\t[WARNING preflightCheckTest]: warning\n"}, // should just print warning
 		{[]Checker{preflightCheckTest{"error"}}, false, ""},
 		{[]Checker{preflightCheckTest{"test"}}, false, ""},
 		{[]Checker{DirAvailableCheck{Path: "/does/not/exist"}}, true, ""},
@@ -281,7 +286,7 @@ func TestRunChecks(t *testing.T) {
 		{[]Checker{FileContentCheck{Path: "/does/not/exist"}}, false, ""},
 		{[]Checker{FileContentCheck{Path: "/"}}, true, ""},
 		{[]Checker{FileContentCheck{Path: "/", Content: []byte("does not exist")}}, false, ""},
-		{[]Checker{InPathCheck{executable: "foobarbaz", exec: exec.New()}}, true, "[preflight] WARNING: foobarbaz not found in system path\n"},
+		{[]Checker{InPathCheck{executable: "foobarbaz", exec: exec.New()}}, true, "\t[WARNING FileExisting-foobarbaz]: foobarbaz not found in system path\n"},
 		{[]Checker{InPathCheck{executable: "foobarbaz", mandatory: true, exec: exec.New()}}, false, ""},
 		{[]Checker{ExtraArgsCheck{
 			APIServerExtraArgs:         map[string]string{"secure-port": "1234"},
@@ -290,14 +295,14 @@ func TestRunChecks(t *testing.T) {
 		}}, true, ""},
 		{[]Checker{ExtraArgsCheck{
 			APIServerExtraArgs: map[string]string{"secure-port": "foo"},
-		}}, true, "[preflight] WARNING: kube-apiserver: failed to parse extra argument --secure-port=foo\n"},
+		}}, true, "\t[WARNING ExtraArgs]: kube-apiserver: failed to parse extra argument --secure-port=foo\n"},
 		{[]Checker{ExtraArgsCheck{
 			APIServerExtraArgs: map[string]string{"invalid-argument": "foo"},
-		}}, true, "[preflight] WARNING: kube-apiserver: failed to parse extra argument --invalid-argument=foo\n"},
+		}}, true, "\t[WARNING ExtraArgs]: kube-apiserver: failed to parse extra argument --invalid-argument=foo\n"},
 	}
 	for _, rt := range tokenTest {
 		buf := new(bytes.Buffer)
-		actual := RunChecks(rt.p, buf)
+		actual := RunChecks(rt.p, buf, sets.NewString())
 		if (actual == nil) != rt.expected {
 			t.Errorf(
 				"failed RunChecks:\n\texpected: %t\n\t  actual: %t",