remove --runtime root flag and make docker the default

cmd/root.go

@@ -47,7 +47,6 @@ import (
 type RootFlags struct {
 	debugLogging bool
 	version      bool
-	runtime      string
 }
 
 var flags = RootFlags{}
@@ -87,7 +86,6 @@ func init() {
 	// add persistent flags (present to all subcommands)
 	// rootCmd.PersistentFlags().StringVar(&cfgFile, "config", "", "config file (default is $HOME/.k3d/config.yaml)")
 	rootCmd.PersistentFlags().BoolVar(&flags.debugLogging, "verbose", false, "Enable verbose output (debug logging)")
-	rootCmd.PersistentFlags().StringVarP(&flags.runtime, "runtime", "r", "docker", "Choose a container runtime environment [docker, containerd]")
 
 	// add local flags
 	rootCmd.Flags().BoolVar(&flags.version, "version", false, "Show k3d and default k3s version")
@@ -150,7 +148,7 @@ func initLogging() {
 }
 
 func initRuntime() {
-	runtime, err := runtimes.GetRuntime(flags.runtime)
+	runtime, err := runtimes.GetRuntime("docker")
 	if err != nil {
 		log.Fatalln(err)
 	}

pkg/runtimes/runtime.go

@@ -35,6 +35,12 @@ import (
 // SelectedRuntime is a runtime (pun intended) variable determining the selected runtime
 var SelectedRuntime Runtime = docker.Docker{}
 
+// Docker docker
+var Docker = docker.Docker{}
+
+// Containerd containerd
+var Containerd = containerd.Containerd{}
+
 // Runtimes defines a map of implemented k3d runtimes
 var Runtimes = map[string]Runtime{
 	"docker":     docker.Docker{},