Add basic bashShell() function

Add the basic frame work for supporting spawning a bash shell by cli
command.

With this change, we can spawn a bash shell in the context of a cluster

$ k3d create -n my-cluster
$ k3d bash -n my-cluster
[my-cluster] $>

// execute commands with KUBECONFIG already set up
[my-cluster] $> kubectl get pods

cli/cluster.go

@@ -161,13 +161,15 @@ func getKubeConfig(cluster string) (string, error) {
 		return "", fmt.Errorf("Cluster %s does not exist", cluster)
 	}
 
-	// If kubeconfig.yaml has not been created, generate it now
-	if _, err := os.Stat(kubeConfigPath); os.IsNotExist(err) {
-		if err = createKubeConfigFile(cluster); err != nil {
+	// If kubeconfi.yaml has not been created, generate it now
+	if _, err := os.Stat(kubeConfigPath); err != nil {
+		if os.IsNotExist(err) {
+			if err = createKubeConfigFile(cluster); err != nil {
+				return "", err
+			}
+		} else {
 			return "", err
 		}
-	} else {
-		return "", err
 	}
 
 	return kubeConfigPath, nil

cli/commands.go

@@ -353,3 +353,7 @@ func GetKubeConfig(c *cli.Context) error {
 	fmt.Println(kubeConfigPath)
 	return nil
 }
+
+func Bash(c *cli.Context) error {
+	return bashShell(c.String("name"))
+}

cli/shell.go

@@ -0,0 +1,31 @@
+package run
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+)
+
+func bashShell(cluster string) error {
+	kubeConfigPath, err := getKubeConfig(cluster)
+	if err != nil {
+		return err
+	}
+	cmd := exec.Command("/bin/bash", "--noprofile", "--norc")
+
+	// Set up stdio
+	cmd.Stdout = os.Stdout
+	cmd.Stdin = os.Stdin
+	cmd.Stderr = os.Stderr
+
+	// Set up Promot
+	setPS1 := fmt.Sprintf("PS1=[%s}%s", cluster, os.Getenv("PS1"))
+
+	// Set up KUBECONFIG
+	setKube := fmt.Sprintf("KUBECONFIG=%s", kubeConfigPath)
+	newEnv := append(os.Environ(), setPS1, setKube)
+
+	cmd.Env = newEnv
+
+	return cmd.Run()
+}

main.go

@@ -45,6 +45,19 @@ func main() {
 			Usage:   "Check if docker is running",
 			Action:  run.CheckTools,
 		},
+		{
+			// bash starts a bash shell in the context of a runnign cluster
+			Name:  "bash",
+			Usage: "Start a bash subshell for a cluster",
+			Flags: []cli.Flag{
+				cli.StringFlag{
+					Name:  "name, n",
+					Value: defaultK3sClusterName,
+					Usage: "Set a name for the cluster",
+				},
+			},
+			Action: run.Bash,
+		},
 		{
 			// create creates a new k3s cluster in docker containers
 			Name:    "create",