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vendor/github.com/mudler/docker-companion/api/unpack.go

@@ -0,0 +1,157 @@
+package api
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+
+	"github.com/docker/docker/pkg/archive"
+	docker "github.com/fsouza/go-dockerclient"
+	jww "github.com/spf13/jwalterweatherman"
+)
+
+// SEPARATOR contains system-specific separator
+const SEPARATOR = string(filepath.Separator)
+
+// ROOTFS is our temporary rootfs path
+const ROOTFS = "." + SEPARATOR + "rootfs_overlay"
+
+// Unpack unpacks a docker image into a path
+func Unpack(client *docker.Client, image string, dirname string, fatal bool) error {
+	var err error
+	r, w := io.Pipe()
+
+	if dirname == "" {
+		dirname = ROOTFS
+	}
+
+	os.MkdirAll(dirname, 0777)
+
+	filename, err := ioutil.TempFile(os.TempDir(), "artemide")
+	if err != nil {
+		return fmt.Errorf("Couldn't create the temporary file")
+	}
+	os.Remove(filename.Name())
+
+	jww.INFO.Println("Creating container")
+
+	container, err := client.CreateContainer(docker.CreateContainerOptions{
+		Config: &docker.Config{
+			Image: image,
+			Cmd:   []string{"true"},
+		},
+	})
+	if err != nil {
+		jww.FATAL.Fatalln("Couldn't export container, sorry", err)
+	}
+	defer func(*docker.Container) {
+		client.RemoveContainer(docker.RemoveContainerOptions{
+			ID:    container.ID,
+			Force: true,
+		})
+	}(container)
+
+	signalchan := make(chan os.Signal, 1)
+	signal.Notify(signalchan,
+		syscall.SIGINT,
+		syscall.SIGTERM,
+		syscall.SIGQUIT)
+
+	go func() {
+		for {
+			s := <-signalchan
+			switch s {
+
+			case syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT:
+				jww.WARN.Println("SIGTERM/SIGINT/SIGQUIT detected, removing pending containers")
+				client.RemoveContainer(docker.RemoveContainerOptions{
+					ID:    container.ID,
+					Force: true,
+				})
+			}
+		}
+	}()
+
+	// writing without a reader will deadlock so write in a goroutine
+	go func() {
+		// it is important to close the writer or reading from the other end of the
+		// pipe will never finish
+		defer w.Close()
+		err := client.ExportContainer(docker.ExportContainerOptions{ID: container.ID, OutputStream: w})
+		if err != nil {
+			jww.FATAL.Fatalln("Couldn't export container, sorry", err)
+		}
+
+	}()
+
+	jww.INFO.Println("Extracting to", dirname)
+
+	err = Untar(r, dirname, true)
+	if err != nil {
+		return fmt.Errorf("could not unpack to " + dirname)
+	}
+	err = prepareRootfs(dirname, fatal)
+
+	return err
+}
+
+func prepareRootfs(dirname string, fatal bool) error {
+
+	_, err := os.Stat(dirname + SEPARATOR + ".dockerenv")
+	if err == nil {
+		err = os.Remove(dirname + SEPARATOR + ".dockerenv")
+		if err != nil {
+			if fatal == true {
+				return fmt.Errorf("could not remove docker env file")
+			} else {
+				jww.WARN.Println("error on remove .dockerenv, extracting anyway")
+			}
+		}
+	}
+
+	_, err = os.Stat(dirname + SEPARATOR + ".dockerinit")
+	if err == nil {
+		err = os.Remove(dirname + SEPARATOR + ".dockerinit")
+		if err != nil {
+			if fatal == true {
+				return fmt.Errorf("could not remove docker init file")
+			} else {
+				jww.WARN.Println("error on remove .dockerinit, extracting anyway")
+			}
+		}
+	}
+
+	err = os.MkdirAll(dirname+SEPARATOR+"dev", 0751)
+	if err != nil {
+		if fatal == true {
+			return fmt.Errorf("could not create dev folder")
+		} else {
+			jww.WARN.Println("could not create dev folder")
+		}
+	}
+
+	// Google DNS as default
+	d1 := []byte("nameserver 8.8.8.8\nnameserver 8.8.4.4\n")
+	err = ioutil.WriteFile(dirname+SEPARATOR+"etc"+SEPARATOR+"resolv.conf", d1, 0644)
+	if err != nil {
+		if fatal == true {
+			return fmt.Errorf("could not write resolv.conf file")
+		} else {
+			jww.WARN.Println("could not create resolv.conf file")
+		}
+	}
+
+	return nil
+}
+
+// Untar just a wrapper around the docker functions
+func Untar(in io.Reader, dest string, sameOwner bool) error {
+	return archive.Untar(in, dest, &archive.TarOptions{
+		NoLchown:        !sameOwner,
+		ExcludePatterns: []string{"dev/"}, // prevent 'operation not permitted'
+	})
+}