add exapmples

Signed-off-by: Jess Frazelle <acidburn@microsoft.com>

.gitignore

@@ -54,5 +54,3 @@ config.json
 .ip
 *.tar
 
-busybox
-alpine

examples/alpine/generate.go

@@ -0,0 +1,18 @@
+// +build ignore
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/genuinetools/binctr/container"
+)
+
+// Pulls an image and saves the binary data in the container package bindata.go.
+func main() {
+	if err := container.EmbedImage("alpine"); err != nil {
+		fmt.Fprintf(os.Stderr, "embed image failed: %v\n", err)
+		os.Exit(1)
+	}
+}

examples/alpine/main.go

@@ -0,0 +1,88 @@
+package main
+
+import (
+	"flag"
+	"os"
+	"runtime"
+
+	"github.com/genuinetools/binctr/container"
+	"github.com/opencontainers/runc/libcontainer"
+	_ "github.com/opencontainers/runc/libcontainer/nsenter"
+	"github.com/sirupsen/logrus"
+)
+
+const (
+	defaultRoot      = "/tmp/binctr-busybox"
+	defaultRootfsDir = "rootfs"
+)
+
+var (
+	containerID string
+	root        string
+)
+
+func init() {
+	// Parse flags
+	flag.StringVar(&containerID, "id", "busybox", "container ID")
+	flag.StringVar(&root, "root", defaultRoot, "root directory of container state, should be tmpfs")
+
+	flag.Usage = func() {
+		flag.PrintDefaults()
+	}
+
+	flag.Parse()
+}
+
+//go:generate go run generate.go
+func main() {
+	if len(os.Args) > 1 && os.Args[1] == "init" {
+		runInit()
+		return
+	}
+
+	// Create a new container spec with the following options.
+	opts := container.SpecOpts{
+		Rootless: true,
+		Terminal: true,
+	}
+	spec := container.Spec(opts)
+
+	// Initialize the container object.
+	c := &container.Container{
+		ID:       containerID,
+		Spec:     spec,
+		Root:     root,
+		Rootless: true,
+	}
+
+	// Unpack the rootfs.
+	if err := c.UnpackRootfs(defaultRootfsDir, Asset); err != nil {
+		logrus.Fatal(err)
+	}
+
+	// Run the container.
+	status, err := c.Run()
+	if err != nil {
+		logrus.Fatal(err)
+	}
+
+	// Remove the rootfs after the container has exited.
+	if err := os.RemoveAll(defaultRootfsDir); err != nil {
+		logrus.Warnf("removing rootfs failed: %v", err)
+	}
+
+	// Exit with the container's exit status.
+	os.Exit(status)
+}
+
+func runInit() {
+	runtime.GOMAXPROCS(1)
+	runtime.LockOSThread()
+	factory, _ := libcontainer.New("")
+	if err := factory.StartInitialization(); err != nil {
+		// as the error is sent back to the parent there is no need to log
+		// or write it to stderr because the parent process will handle this
+		os.Exit(1)
+	}
+	panic("libcontainer: container init failed to exec")
+}