Add --file flag to 'minikube logs' to automatically put logs into a file.

cmd/minikube/cmd/logs.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/spf13/viper"
+	"k8s.io/klog/v2"
 	cmdcfg "k8s.io/minikube/cmd/minikube/cmd/config"
 	"k8s.io/minikube/pkg/minikube/cluster"
 	"k8s.io/minikube/pkg/minikube/cruntime"
@@ -44,6 +45,8 @@ var (
 	numberOfLines int
 	// showProblems only shows lines that match known issues
 	showProblems bool
+	// fileOutput is where to write logs to. If omitted, writes to stdout.
+	fileOutput string
 )
 
 // logsCmd represents the logs command
@@ -52,7 +55,23 @@ var logsCmd = &cobra.Command{
 	Short: "Returns logs to debug a local Kubernetes cluster",
 	Long:  `Gets the logs of the running instance, used for debugging minikube, not user code.`,
 	Run: func(cmd *cobra.Command, args []string) {
-		logs.OutputOffline(numberOfLines)
+		var logOutput *os.File = os.Stdout
+		var err error
+
+		if fileOutput != "" {
+			logOutput, err = os.Create(fileOutput)
+			defer func() {
+				err := logOutput.Close()
+				if err != nil {
+					klog.Warning("Failed to close file: %v", err)
+				}
+			}()
+			if err != nil {
+				exit.Error(reason.Usage, "Failed to create file", err)
+			}
+		}
+
+		logs.OutputOffline(numberOfLines, logOutput)
 
 		co := mustload.Running(ClusterFlagValue())
 
@@ -65,19 +84,20 @@ var logsCmd = &cobra.Command{
 		if err != nil {
 			exit.Error(reason.InternalNewRuntime, "Unable to get runtime", err)
 		}
+
 		if followLogs {
-			err := logs.Follow(cr, bs, *co.Config, co.CP.Runner)
+			err := logs.Follow(cr, bs, *co.Config, co.CP.Runner, logOutput)
 			if err != nil {
 				exit.Error(reason.InternalLogFollow, "Follow", err)
 			}
 			return
 		}
 		if showProblems {
 			problems := logs.FindProblems(cr, bs, *co.Config, co.CP.Runner)
-			logs.OutputProblems(problems, numberOfProblems)
+			logs.OutputProblems(problems, numberOfProblems, logOutput)
 			return
 		}
-		err = logs.Output(cr, bs, *co.Config, co.CP.Runner, numberOfLines)
+		err = logs.Output(cr, bs, *co.Config, co.CP.Runner, numberOfLines, logOutput)
 		if err != nil {
 			out.Ln("")
 			// Avoid exit.Error, since it outputs the issue URL
@@ -92,4 +112,5 @@ func init() {
 	logsCmd.Flags().BoolVar(&showProblems, "problems", false, "Show only log entries which point to known problems")
 	logsCmd.Flags().IntVarP(&numberOfLines, "length", "n", 60, "Number of lines back to go within the log")
 	logsCmd.Flags().StringVar(&nodeName, "node", "", "The node to get logs from. Defaults to the primary control plane.")
+	logsCmd.Flags().StringVar(&fileOutput, "file", "", "If present, writes to the provided file instead of stdout.")
 }

pkg/minikube/bootstrapper/bsutil/kverify/system_pods.go

@@ -20,6 +20,7 @@ package kverify
 import (
 	"context"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -150,7 +151,7 @@ func podStatusMsg(pod core.Pod) string {
 func announceProblems(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.ClusterConfig, cr command.Runner) {
 	problems := logs.FindProblems(r, bs, cfg, cr)
 	if len(problems) > 0 {
-		logs.OutputProblems(problems, 5)
+		logs.OutputProblems(problems, 5, os.Stderr)
 		time.Sleep(kconst.APICallRetryInterval * 15)
 	}
 }

pkg/minikube/logs/logs.go

@@ -21,6 +21,7 @@ import (
 	"bufio"
 	"bytes"
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"regexp"
@@ -93,16 +94,16 @@ type logRunner interface {
 const lookBackwardsCount = 400
 
 // Follow follows logs from multiple files in tail(1) format
-func Follow(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.ClusterConfig, cr logRunner) error {
+func Follow(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.ClusterConfig, cr logRunner, logOutput io.Writer) error {
 	cs := []string{}
 	for _, v := range logCommands(r, bs, cfg, 0, true) {
 		cs = append(cs, v+" &")
 	}
 	cs = append(cs, "wait")
 
 	cmd := exec.Command("/bin/bash", "-c", strings.Join(cs, " "))
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stdout
+	cmd.Stdout = logOutput
+	cmd.Stderr = logOutput
 	if _, err := cr.RunCmd(cmd); err != nil {
 		return errors.Wrapf(err, "log follow")
 	}
@@ -146,7 +147,10 @@ func FindProblems(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.C
 }
 
 // OutputProblems outputs discovered problems.
-func OutputProblems(problems map[string][]string, maxLines int) {
+func OutputProblems(problems map[string][]string, maxLines int, logOutput *os.File) {
+	out.SetErrFile(logOutput)
+	defer out.SetErrFile(os.Stderr)
+
 	for name, lines := range problems {
 		out.FailureT("Problems detected in {{.name}}:", out.V{"name": name})
 		if len(lines) > maxLines {
@@ -159,7 +163,7 @@ func OutputProblems(problems map[string][]string, maxLines int) {
 }
 
 // Output displays logs from multiple sources in tail(1) format
-func Output(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.ClusterConfig, runner command.Runner, lines int) error {
+func Output(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.ClusterConfig, runner command.Runner, lines int, logOutput *os.File) error {
 	cmds := logCommands(r, bs, cfg, lines, false)
 	cmds["kernel"] = "uptime && uname -a && grep PRETTY /etc/os-release"
 
@@ -168,6 +172,9 @@ func Output(r cruntime.Manager, bs bootstrapper.Bootstrapper, cfg config.Cluster
 		names = append(names, k)
 	}
 
+	out.SetOutFile(logOutput)
+	defer out.SetOutFile(os.Stdout)
+
 	sort.Strings(names)
 	failed := []string{}
 	for i, name := range names {
@@ -238,13 +245,16 @@ func outputLastStart() error {
 }
 
 // OutputOffline outputs logs that don't need a running cluster.
-func OutputOffline(lines int) {
+func OutputOffline(lines int, logOutput *os.File) {
+	out.SetOutFile(logOutput)
+	defer out.SetOutFile(os.Stdout)
 	if err := outputAudit(lines); err != nil {
 		klog.Errorf("failed to output audit logs: %v", err)
 	}
 	if err := outputLastStart(); err != nil {
 		klog.Errorf("failed to output last start logs: %v", err)
 	}
+
 	out.Styled(style.Empty, "")
 }
 

site/content/en/docs/commands/logs.md

@@ -20,6 +20,7 @@ minikube logs [flags]
 ### Options
 
 ```
+      --file string   If present, writes to the provided file instead of stdout.
   -f, --follow        Show only the most recent journal entries, and continuously print new entries as they are appended to the journal.
   -n, --length int    Number of lines back to go within the log (default 60)
       --node string   The node to get logs from. Defaults to the primary control plane.

test/integration/functional_test.go

@@ -118,6 +118,7 @@ func TestFunctional(t *testing.T) {
 			{"DryRun", validateDryRun},
 			{"StatusCmd", validateStatusCmd},
 			{"LogsCmd", validateLogsCmd},
+			{"LogsFileCmd", validateLogsFileCmd},
 			{"MountCmd", validateMountCmd},
 			{"ProfileCmd", validateProfileCmd},
 			{"ServiceCmd", validateServiceCmd},
@@ -1057,12 +1058,7 @@ func validateConfigCmd(ctx context.Context, t *testing.T, profile string) {
 	}
 }
 
-// validateLogsCmd asserts basic "logs" command functionality
-func validateLogsCmd(ctx context.Context, t *testing.T, profile string) {
-	rr, err := Run(t, exec.CommandContext(ctx, Target(), "-p", profile, "logs"))
-	if err != nil {
-		t.Errorf("%s failed: %v", rr.Command(), err)
-	}
+func checkSaneLogs(t *testing.T, logs string) {
 	expectedWords := []string{"apiserver", "Linux", "kubelet", "Audit", "Last Start"}
 	switch ContainerRuntime() {
 	case "docker":
@@ -1074,12 +1070,46 @@ func validateLogsCmd(ctx context.Context, t *testing.T, profile string) {
 	}
 
 	for _, word := range expectedWords {
-		if !strings.Contains(rr.Stdout.String(), word) {
-			t.Errorf("expected minikube logs to include word: -%q- but got \n***%s***\n", word, rr.Output())
+		if !strings.Contains(logs, word) {
+			t.Errorf("expected minikube logs to include word: -%q- but got \n***%s***\n", word, logs)
 		}
 	}
 }
 
+// validateLogsCmd asserts basic "logs" command functionality
+func validateLogsCmd(ctx context.Context, t *testing.T, profile string) {
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), "-p", profile, "logs"))
+	if err != nil {
+		t.Errorf("%s failed: %v", rr.Command(), err)
+	}
+
+	checkSaneLogs(t, rr.Stdout.String())
+}
+
+// validateLogsFileCmd asserts "logs --file" command functionality
+func validateLogsFileCmd(ctx context.Context, t *testing.T, profile string) {
+	dname, err := ioutil.TempDir("", profile)
+	if err != nil {
+		t.Fatalf("Cannot create temp dir: %v", err)
+	}
+	logFileName := filepath.Join(dname, "logs.txt")
+
+	rr, err := Run(t, exec.CommandContext(ctx, Target(), "-p", profile, "logs", "--file", logFileName))
+	if err != nil {
+		t.Errorf("%s failed: %v", rr.Command(), err)
+	}
+	if rr.Stdout.String() != "" {
+		t.Errorf("expected empty minikube logs output, but got: \n***%s***\n", rr.Output())
+	}
+
+	logs, err := ioutil.ReadFile(logFileName)
+	if err != nil {
+		t.Errorf("Failed to read logs output '%s': %v", logFileName, err)
+	}
+
+	checkSaneLogs(t, string(logs))
+}
+
 // validateProfileCmd asserts "profile" command functionality
 func validateProfileCmd(ctx context.Context, t *testing.T, profile string) {
 	t.Run("profile_not_create", func(t *testing.T) {