Merge pull request #737 from umohnani8/kpod_export

Add 'kpod export' command

cmd/kpod/export.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"io"
+	"os"
+
+	"fmt"
+
+	"github.com/containers/storage"
+	"github.com/containers/storage/pkg/archive"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"github.com/urfave/cli"
+)
+
+type exportOptions struct {
+	output    string
+	container string
+}
+
+var (
+	exportFlags = []cli.Flag{
+		cli.StringFlag{
+			Name:  "output, o",
+			Usage: "Write to a file, default is STDOUT",
+			Value: "/dev/stdout",
+		},
+	}
+	exportDescription = "Exports container's filesystem contents as a tar archive" +
+		" and saves it on the local machine."
+	exportCommand = cli.Command{
+		Name:        "export",
+		Usage:       "Export container's filesystem contents as a tar archive",
+		Description: exportDescription,
+		Flags:       exportFlags,
+		Action:      exportCmd,
+		ArgsUsage:   "CONTAINER",
+	}
+)
+
+// exportCmd saves a container to a tarball on disk
+func exportCmd(c *cli.Context) error {
+	args := c.Args()
+	if len(args) == 0 {
+		return errors.Errorf("container id must be specified")
+	}
+	if len(args) > 1 {
+		return errors.Errorf("too many arguments given, need 1 at most.")
+	}
+	container := args[0]
+
+	config, err := getConfig(c)
+	if err != nil {
+		return errors.Wrapf(err, "could not get config")
+	}
+	store, err := getStore(config)
+	if err != nil {
+		return err
+	}
+
+	output := c.String("output")
+	if output == "/dev/stdout" {
+		file := os.Stdout
+		if logrus.IsTerminal(file) {
+			return errors.Errorf("refusing to export to terminal. Use -o flag or redirect")
+		}
+	}
+
+	opts := exportOptions{
+		output:    output,
+		container: container,
+	}
+
+	return exportContainer(store, opts)
+}
+
+// exportContainer exports the contents of a container and saves it as
+// a tarball on disk
+func exportContainer(store storage.Store, opts exportOptions) error {
+	mountPoint, err := store.Mount(opts.container, "")
+	if err != nil {
+		return errors.Wrapf(err, "error finding container %q", opts.container)
+	}
+	defer func() {
+		if err := store.Unmount(opts.container); err != nil {
+			fmt.Printf("error unmounting container %q: %v\n", opts.container, err)
+		}
+	}()
+
+	input, err := archive.Tar(mountPoint, archive.Uncompressed)
+	if err != nil {
+		return errors.Wrapf(err, "error reading container directory %q", opts.container)
+	}
+
+	outFile, err := os.Create(opts.output)
+	if err != nil {
+		return errors.Wrapf(err, "error creating file %q", opts.output)
+	}
+	defer outFile.Close()
+
+	_, err = io.Copy(outFile, input)
+	return err
+}

cmd/kpod/main.go

@@ -22,6 +22,7 @@ func main() {
 	app.Version = Version
 
 	app.Commands = []cli.Command{
+		exportCommand,
 		historyCommand,
 		imagesCommand,
 		infoCommand,