✨ Add support to clusterctl for inserting workload kubeconfig into an existing kubeconfig file

Author: dmvolod

cmd/clusterctl/cmd/get_kubeconfig.go

@@ -19,9 +19,11 @@ package cmd
 import (
 	"context"
 	"fmt"
+	"os"
 
 	"github.com/pkg/errors"
 	"github.com/spf13/cobra"
+	"k8s.io/client-go/tools/clientcmd"
 
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
 	"sigs.k8s.io/cluster-api/cmd/clusterctl/client"
@@ -32,6 +34,7 @@ type getKubeconfigOptions struct {
 	kubeconfig        string
 	kubeconfigContext string
 	namespace         string
+	intoKubeconfig    bool
 }
 
 var gk = &getKubeconfigOptions{}
@@ -67,6 +70,8 @@ func init() {
 		"Path to the kubeconfig file to use for accessing the management cluster. If unspecified, default discovery rules apply.")
 	getKubeconfigCmd.Flags().StringVar(&gk.kubeconfigContext, "kubeconfig-context", "",
 		"Context to be used within the kubeconfig file. If empty, current context will be used.")
+	getKubeconfigCmd.Flags().BoolVar(&gk.intoKubeconfig, "into-kubeconfig", false,
+		"Inserts the workload cluster kubeconfig into the kubeconfig file.")
 
 	// completions
 	getKubeconfigCmd.ValidArgsFunction = resourceNameCompletionFunc(
@@ -98,6 +103,34 @@ func runGetKubeconfig(workloadClusterName string) error {
 	if err != nil {
 		return err
 	}
+	if gk.intoKubeconfig {
+		return intoKubeconfig(out)
+	}
+
 	fmt.Println(out)
 	return nil
 }
+
+func intoKubeconfig(kubeconfig string) error {
+	kubeconfigFile, err := os.CreateTemp("", "kubeconfig")
+	if err != nil {
+		return err
+	}
+	defer os.Remove(kubeconfigFile.Name())
+
+	if _, err = kubeconfigFile.WriteString(kubeconfig); err != nil {
+		return err
+	}
+	if err = kubeconfigFile.Close(); err != nil {
+		return err
+	}
+
+	rules := clientcmd.NewDefaultClientConfigLoadingRules()
+	rules.Precedence = append(rules.Precedence, kubeconfigFile.Name())
+	config, err := rules.Load()
+	if err != nil {
+		return err
+	}
+
+	return clientcmd.WriteToFile(*config, rules.Precedence[0])
+}

docs/book/src/clusterctl/commands/get-kubeconfig.md

@@ -1,6 +1,6 @@
 # clusterctl get kubeconfig
 
-This command prints the kubeconfig of an existing workload cluster into stdout.
+This command prints the kubeconfig of an existing workload cluster into stdout or inserts it into the default or defined kubeconfig file.
 This functionality is available in clusterctl v0.3.9 or newer.
 
 ## Examples
@@ -11,6 +11,12 @@ Get the kubeconfig of a workload cluster named foo.
 clusterctl get kubeconfig foo
 ```
 
+Get the kubeconfig of a workload cluster named foo and insert it into the default kubeconfig file.
+
+```bash
+clusterctl get kubeconfig foo --into-kubeconfig
+```
+
 Get the kubeconfig of a workload cluster named foo in the namespace bar
 
 ```bash