moby: Add a 'run' command to execute an image on hyperkit

'moby run' will use the kernel and initrd image produced
by 'moby build' and, on macOS, will run it inside a
hyperkit VM. This assumes that you have a recent version
of Docker for Mac installed as it re-uses the hyperkit
and VPNKit from it.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

src/cmd/moby/main.go

@@ -100,6 +100,7 @@ func main() {
 		fmt.Printf("USAGE: %s COMMAND\n\n", os.Args[0])
 		fmt.Printf("Commands:\n")
 		fmt.Printf("  build       Build a Moby image from a YAML file\n")
+		fmt.Printf("  run         Run a Moby image on a local hypervisor\n")
 		fmt.Printf("  help        Print this message\n")
 		fmt.Printf("\n")
 		fmt.Printf("Run '%s COMMAND --help' for more information on the command\n", os.Args[0])
@@ -114,6 +115,23 @@ func main() {
 	}
 	buildName := buildCmd.String("name", "", "Name to use for output files")
 
+	runCmd := flag.NewFlagSet("run", flag.ExitOnError)
+	runCmd.Usage = func() {
+		fmt.Printf("USAGE: %s run [options] [prefix]\n\n", os.Args[0])
+		fmt.Printf("'prefix' specifies the path to the VM image.\n")
+		fmt.Printf("It defaults to './moby'.\n")
+		fmt.Printf("\n")
+		fmt.Printf("Options:\n")
+		runCmd.PrintDefaults()
+		fmt.Printf("\n")
+		fmt.Printf("If 'data' is supplied or if 'background' is selected\n")
+		fmt.Printf("some per VM state is kept in a sub-directory in the ~/.moby\n")
+	}
+	runCPUs := runCmd.Int("cpus", 1, "Number of CPUs")
+	runMem := runCmd.Int("mem", 1024, "Amount of memory in MB")
+	runDiskSz := runCmd.Int("disk-size", 0, "Size of Disk in MB")
+	runDisk := runCmd.String("disk", "", "Path to disk image to used")
+
 	if len(os.Args) < 2 {
 		fmt.Printf("Please specify a command.\n\n")
 		flag.Usage()
@@ -124,6 +142,9 @@ func main() {
 	case "build":
 		buildCmd.Parse(os.Args[2:])
 		build(*buildName, buildCmd.Args())
+	case "run":
+		runCmd.Parse(os.Args[2:])
+		run(*runCPUs, *runMem, *runDiskSz, *runDisk, runCmd.Args())
 	case "help":
 		flag.Usage()
 	default:

src/cmd/moby/run_darwin.go

@@ -0,0 +1,51 @@
+// +build darwin
+
+package main
+
+import (
+	"io/ioutil"
+	"log"
+	"os"
+	"os/user"
+
+	"github.com/docker/hyperkit/go"
+)
+
+func run(cpus, mem, diskSz int, disk string, args []string) {
+	prefix := "moby"
+	if len(args) > 0 {
+		prefix = args[0]
+	}
+
+	cmdline, err := ioutil.ReadFile(prefix + "-cmdline")
+	if err != nil {
+		log.Fatalf("Cannot open cmdline file: %v", err)
+	}
+
+	if diskSz != 0 && disk == "" {
+		disk = prefix + "-disk.img"
+	}
+
+	h, err := hyperkit.New("", "", "auto", disk)
+	if err != nil {
+		log.Fatalln("Error creating hyperkit: ", err)
+	}
+
+	h.Kernel = prefix + "-bzImage"
+	h.Initrd = prefix + "-initrd.img"
+	h.CPUs = cpus
+	h.Memory = mem
+	h.DiskSize = diskSz
+
+	err = h.Run(string(cmdline))
+	if err != nil {
+		log.Fatalf("Cannot run hyperkit: %v", err)
+	}
+}
+
+func getHome() string {
+	if usr, err := user.Current(); err == nil {
+		return usr.HomeDir
+	}
+	return os.Getenv("HOME")
+}

src/cmd/moby/run_fallback.go

@@ -0,0 +1,11 @@
+// +build !darwin
+
+package main
+
+import (
+	"log"
+)
+
+func run(cpus, mem, diskSz int, userData string, args []string) {
+	log.Fatalf("'run' is not support yet on your OS")
+}