add import-image command for importing single image

cli/cluster.go

@@ -68,6 +68,10 @@ func createClusterDir(name string) {
 	if err := createDirIfNotExists(clusterPath); err != nil {
 		log.Fatalf("ERROR: couldn't create cluster directory [%s] -> %+v", clusterPath, err)
 	}
+	// create subdir for sharing container images
+	if err := createDirIfNotExists(clusterPath + "/images"); err != nil {
+		log.Fatalf("ERROR: couldn't create cluster sub-directory [%s] -> %+v", clusterPath+"/images", err)
+	}
 }
 
 // deleteClusterDir contrary to createClusterDir, this deletes the cluster directory under $HOME/.config/k3d/<cluster_name>

cli/commands.go

@@ -100,7 +100,7 @@ func CreateCluster(c *cli.Context) error {
 	if c.IsSet("port") {
 		log.Println("INFO: As of v2.0.0 --port will be used for arbitrary port mapping. Please use --api-port/-a instead for configuring the Api Port")
 	}
-	apiPort, err := parseApiPort(c.String("api-port"))
+	apiPort, err := parseAPIPort(c.String("api-port"))
 	if err != nil {
 		return err
 	}
@@ -111,7 +111,7 @@ func CreateCluster(c *cli.Context) error {
 	if apiPort.Host == "" {
 		apiPort.Host, err = getDockerMachineIp()
 		// IP address is the same as the host
-		apiPort.HostIp = apiPort.Host
+		apiPort.HostIP = apiPort.Host
 		// In case of error, Log a warning message, and continue on. Since it more likely caused by a miss configured
 		// DOCKER_MACHINE_NAME environment variable.
 		if err != nil {
@@ -137,7 +137,7 @@ func CreateCluster(c *cli.Context) error {
 
 	clusterSpec := &ClusterSpec{
 		AgentArgs:         []string{},
-		ApiPort:           *apiPort,
+		APIPort:           *apiPort,
 		AutoRestart:       c.Bool("auto-restart"),
 		ClusterName:       c.String("name"),
 		Env:               env,
@@ -151,6 +151,10 @@ func CreateCluster(c *cli.Context) error {
 
 	// create the server
 	log.Printf("Creating cluster [%s]", c.String("name"))
+
+	// create the directory where we will put the kubeconfig file by default (when running `k3d get-config`)
+	createClusterDir(c.String("name"))
+
 	dockerID, err := createServer(clusterSpec)
 	if err != nil {
 		deleteCluster()
@@ -192,10 +196,6 @@ func CreateCluster(c *cli.Context) error {
 		time.Sleep(1 * time.Second)
 	}
 
-	// create the directory where we will put the kubeconfig file by default (when running `k3d get-config`)
-	// TODO: this can probably be moved to `k3d get-config` or be removed in a different approach
-	createClusterDir(c.String("name"))
-
 	// spin up the worker nodes
 	// TODO: do this concurrently in different goroutines
 	if c.Int("workers") > 0 {
@@ -362,3 +362,8 @@ func GetKubeConfig(c *cli.Context) error {
 func Shell(c *cli.Context) error {
 	return subShell(c.String("name"), c.String("shell"), c.String("command"))
 }
+
+// ImportImage saves an image locally and imports it into the k3d containers
+func ImportImage(c *cli.Context) error {
+	return importImage(c.String("name"), c.String("image"))
+}

cli/container.go

@@ -22,7 +22,7 @@ import (
 
 type ClusterSpec struct {
 	AgentArgs         []string
-	ApiPort           apiPort
+	APIPort           apiPort
 	AutoRestart       bool
 	ClusterName       string
 	Env               []string
@@ -94,14 +94,14 @@ func createServer(spec *ClusterSpec) (string, error) {
 		return "", err
 	}
 
-	hostIp := "0.0.0.0"
+	hostIP := "0.0.0.0"
 	containerLabels["apihost"] = "localhost"
-	if spec.ApiPort.Host != "" {
-		hostIp = spec.ApiPort.HostIp
-		containerLabels["apihost"] = spec.ApiPort.Host
+	if spec.APIPort.Host != "" {
+		hostIP = spec.APIPort.HostIP
+		containerLabels["apihost"] = spec.APIPort.Host
 	}
 
-	apiPortSpec := fmt.Sprintf("%s:%s:%s/tcp", hostIp, spec.ApiPort.Port, spec.ApiPort.Port)
+	apiPortSpec := fmt.Sprintf("%s:%s:%s/tcp", hostIP, spec.APIPort.Port, spec.APIPort.Port)
 
 	serverPorts = append(serverPorts, apiPortSpec)
 
@@ -123,6 +123,13 @@ func createServer(spec *ClusterSpec) (string, error) {
 		hostConfig.Binds = spec.Volumes
 	}
 
+	// we need to mount the clusterDir subdirectory `clusterDir/images` to enable importing images without the need for `docker cp`
+	clusterDir, err := getClusterDir(spec.ClusterName)
+	if err != nil {
+		return "", fmt.Errorf("ERROR: couldn't get cluster dir for mounting\n%+v", err)
+	}
+	hostConfig.Binds = append(hostConfig.Binds, fmt.Sprintf("%s:/images", clusterDir+"/images"))
+
 	networkingConfig := &network.NetworkingConfig{
 		EndpointsConfig: map[string]*network.EndpointSettings{
 			k3dNetworkName(spec.ClusterName): {
@@ -157,7 +164,7 @@ func createWorker(spec *ClusterSpec, postfix int) (string, error) {
 
 	containerName := GetContainerName("worker", spec.ClusterName, postfix)
 
-	env := append(spec.Env, fmt.Sprintf("K3S_URL=https://k3d-%s-server:%s", spec.ClusterName, spec.ApiPort.Port))
+	env := append(spec.Env, fmt.Sprintf("K3S_URL=https://k3d-%s-server:%s", spec.ClusterName, spec.APIPort.Port))
 
 	// ports to be assigned to the server belong to roles
 	// all, server or <server-container-name>
@@ -192,6 +199,13 @@ func createWorker(spec *ClusterSpec, postfix int) (string, error) {
 		hostConfig.Binds = spec.Volumes
 	}
 
+	// we need to mount the clusterDir subdirectory `clusterDir/images` to enable importing images without the need for `docker cp`
+	clusterDir, err := getClusterDir(spec.ClusterName)
+	if err != nil {
+		return "", fmt.Errorf("ERROR: couldn't get cluster dir for mounting\n%+v", err)
+	}
+	hostConfig.Binds = append(hostConfig.Binds, fmt.Sprintf("%s:/images", clusterDir+"/images"))
+
 	networkingConfig := &network.NetworkingConfig{
 		EndpointsConfig: map[string]*network.EndpointSettings{
 			k3dNetworkName(spec.ClusterName): {

cli/image.go

@@ -0,0 +1,131 @@
+package run
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/docker/docker/api/types"
+	"github.com/docker/docker/client"
+)
+
+const imageBasePathRemote = "/images/"
+
+func importImage(clusterName, image string) error {
+	// get a docker client
+	ctx := context.Background()
+	docker, err := client.NewEnvClient()
+	if err != nil {
+		return fmt.Errorf("ERROR: couldn't create docker client\n%+v", err)
+	}
+
+	// get cluster directory to temporarily save the image tarball there
+	imageBasePathLocal, err := getClusterDir(clusterName)
+	imageBasePathLocal = imageBasePathLocal + "/images/"
+	if err != nil {
+		return fmt.Errorf("ERROR: couldn't get cluster directory for cluster [%s]\n%+v", clusterName, err)
+	}
+
+	// TODO: extend to enable importing a list of images
+	imageList := []string{image}
+
+	//*** first, save the images using the local docker daemon
+	log.Printf("INFO: Saving image [%s] from local docker daemon...", image)
+	imageReader, err := docker.ImageSave(ctx, imageList)
+	if err != nil {
+		return fmt.Errorf("ERROR: failed to save image [%s] locally\n%+v", image, err)
+	}
+
+	// create tarball
+	imageTarName := strings.ReplaceAll(strings.ReplaceAll(image, ":", "_"), "/", "_") + ".tar"
+	imageTar, err := os.Create(imageBasePathLocal + imageTarName)
+	if err != nil {
+		return err
+	}
+	defer imageTar.Close()
+
+	_, err = io.Copy(imageTar, imageReader)
+	if err != nil {
+		return fmt.Errorf("ERROR: couldn't save image [%s] to file [%s]\n%+v", image, imageTar.Name(), err)
+	}
+
+	// TODO: get correct container ID by cluster name
+	clusters, err := getClusters(false, clusterName)
+	if err != nil {
+		return fmt.Errorf("ERROR: couldn't get cluster by name [%s]\n%+v", clusterName, err)
+	}
+	containerList := []types.Container{clusters[clusterName].server}
+	containerList = append(containerList, clusters[clusterName].workers...)
+
+	// *** second, import the images using ctr in the k3d nodes
+
+	// create exec configuration
+	cmd := []string{"ctr", "image", "import", imageBasePathRemote + imageTarName}
+	execConfig := types.ExecConfig{
+		AttachStderr: true,
+		AttachStdout: true,
+		Cmd:          cmd,
+		Tty:          true,
+		Detach:       true,
+	}
+
+	execAttachConfig := types.ExecConfig{
+		Tty: true,
+	}
+
+	execStartConfig := types.ExecStartCheck{
+		Tty: true,
+	}
+
+	// import in each node separately
+	// TODO: create a shared image cache volume, so we don't need to import it separately
+	for _, container := range containerList {
+
+		containerName := container.Names[0][1:] // trimming the leading "/" from name
+		log.Printf("INFO: Importing image [%s] in container [%s]", image, containerName)
+
+		// create exec configuration
+		execResponse, err := docker.ContainerExecCreate(ctx, container.ID, execConfig)
+		if err != nil {
+			return fmt.Errorf("ERROR: Failed to create exec command for container [%s]\n%+v", containerName, err)
+		}
+
+		// attach to exec process in container
+		containerConnection, err := docker.ContainerExecAttach(ctx, execResponse.ID, execAttachConfig)
+		if err != nil {
+			return fmt.Errorf("ERROR: couldn't attach to container [%s]\n%+v", containerName, err)
+		}
+		defer containerConnection.Close()
+
+		// start exec
+		err = docker.ContainerExecStart(ctx, execResponse.ID, execStartConfig)
+		if err != nil {
+			return fmt.Errorf("ERROR: couldn't execute command in container [%s]\n%+v", containerName, err)
+		}
+
+		// get output from container
+		content, err := ioutil.ReadAll(containerConnection.Reader)
+		if err != nil {
+			return fmt.Errorf("ERROR: couldn't read output from container [%s]\n%+v", containerName, err)
+		}
+
+		// example output "unpacking image........ ...done"
+		if !strings.Contains(string(content), "done") {
+			return fmt.Errorf("ERROR: seems like something went wrong using `ctr image import` in container [%s]. Full output below:\n%s", containerName, string(content))
+		}
+	}
+
+	log.Printf("INFO: Successfully imported image [%s] in all nodes of cluster [%s]", image, clusterName)
+
+	log.Println("INFO: Cleaning up tarball...")
+	if err := os.Remove(imageBasePathLocal + imageTarName); err != nil {
+		return fmt.Errorf("ERROR: Couldn't remove tarball [%s]\n%+v", imageBasePathLocal+imageTarName, err)
+	}
+	log.Println("INFO: ...Done")
+
+	return nil
+}

cli/util.go

@@ -11,7 +11,7 @@ import (
 
 type apiPort struct {
 	Host   string
-	HostIp string
+	HostIP string
 	Port   string
 }
 
@@ -90,7 +90,7 @@ func ValidateHostname(name string) error {
 	return nil
 }
 
-func parseApiPort(portSpec string) (*apiPort, error) {
+func parseAPIPort(portSpec string) (*apiPort, error) {
 	var port *apiPort
 	split := strings.Split(portSpec, ":")
 	if len(split) > 2 {
@@ -105,7 +105,7 @@ func parseApiPort(portSpec string) (*apiPort, error) {
 		if err != nil {
 			return nil, err
 		}
-		port = &apiPort{Host: split[0], HostIp: addrs[0], Port: split[1]}
+		port = &apiPort{Host: split[0], HostIP: addrs[0], Port: split[1]}
 	}
 
 	// Verify 'port' is an integer and within port ranges

main.go

@@ -214,6 +214,23 @@ func main() {
 			},
 			Action: run.GetKubeConfig,
 		},
+		{
+			// get-kubeconfig grabs the kubeconfig from the cluster and prints the path to it
+			Name:  "import-image",
+			Usage: "Import a container image from your local docker daemon into the cluster",
+			Flags: []cli.Flag{
+				cli.StringFlag{
+					Name:  "name, n",
+					Value: defaultK3sClusterName,
+					Usage: "Name of the cluster",
+				},
+				cli.StringFlag{
+					Name:  "image, i",
+					Usage: "Name of the image that you want to import, e.g. `nginx:local`",
+				},
+			},
+			Action: run.ImportImage,
+		},
 	}
 
 	// Global flags