podman/cmd/kpod/import.go

package main

import (
	"fmt"
	"io"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/pkg/errors"
	"github.com/projectatomic/libpod/libpod"
	"github.com/urfave/cli"
)

var (
	importFlags = []cli.Flag{
		cli.StringSliceFlag{
			Name:  "change, c",
			Usage: "Apply the following possible instructions to the created image (default []): CMD | ENTRYPOINT | ENV | EXPOSE | LABEL | STOPSIGNAL | USER | VOLUME | WORKDIR",
		},
		cli.StringFlag{
			Name:  "message, m",
			Usage: "Set commit message for imported image",
		},
	}
	importDescription = `Create a container image from the contents of the specified tarball (.tar, .tar.gz, .tgz, .bzip, .tar.xz, .txz).
	 Note remote tar balls can be specified, via web address.
	 Optionally tag the image. You can specify the Dockerfile instructions using the --change option.
	`
	importCommand = cli.Command{
		Name:        "import",
		Usage:       "Import a tarball to create a filesystem image",
		Description: importDescription,
		Flags:       importFlags,
		Action:      importCmd,
		ArgsUsage:   "TARBALL [REFERENCE]",
	}
)

func importCmd(c *cli.Context) error {
	if err := validateFlags(c, importFlags); err != nil {
		return err
	}

	runtime, err := getRuntime(c)
	if err != nil {
		return errors.Wrapf(err, "could not get runtime")
	}
	defer runtime.Shutdown(false)

	var opts libpod.CopyOptions
	var source string
	args := c.Args()
	switch len(args) {
	case 0:
		return errors.Errorf("need to give the path to the tarball, or must specify a tarball of '-' for stdin")
	case 1:
		source = args[0]
	case 2:
		source = args[0]
		opts.Reference = args[1]
	default:
		return errors.Errorf("too many arguments. Usage TARBALL [REFERENCE]")
	}

	changes := v1.ImageConfig{}
	if c.IsSet("change") {
		changes, err = getImageConfig(c.StringSlice("change"))
		if err != nil {
			return errors.Wrapf(err, "error adding config changes to image %q", source)
		}
	}

	history := []v1.History{
		{Comment: c.String("message")},
	}

	config := v1.Image{
		Config:  changes,
		History: history,
	}

	opts.ImageConfig = config

	// if source is a url, download it and save to a temp file
	u, err := url.ParseRequestURI(source)
	if err == nil && u.Scheme != "" {
		file, err := downloadFromURL(source)
		if err != nil {
			return err
		}
		defer os.Remove(file)
		source = file
	}

	return runtime.ImportImage(source, opts)
}

// donwloadFromURL downloads an image in the format "https:/example.com/myimage.tar"
// and tempoarily saves in it /var/tmp/importxyz, which is deleted after the image is imported
func downloadFromURL(source string) (string, error) {
	fmt.Printf("Downloading from %q\n", source)

	outFile, err := ioutil.TempFile("/var/tmp", "import")
	if err != nil {
		return "", errors.Wrap(err, "error creating file")
	}
	defer outFile.Close()

	response, err := http.Get(source)
	if err != nil {
		return "", errors.Wrapf(err, "error downloading %q", source)
	}
	defer response.Body.Close()

	_, err = io.Copy(outFile, response.Body)
	if err != nil {
		return "", errors.Wrapf(err, "error saving %q to %q", source, outFile)
	}

	return outFile.Name(), nil
}

// getImageConfig converts the --change flag values in the format "CMD=/bin/bash USER=example"
// to a type v1.ImageConfig
func getImageConfig(changes []string) (v1.ImageConfig, error) {
	// USER=value | EXPOSE=value | ENV=value | ENTRYPOINT=value |
	// CMD=value | VOLUME=value | WORKDIR=value | LABEL=key=value | STOPSIGNAL=value

	var (
		user       string
		env        []string
		entrypoint []string
		cmd        []string
		workingDir string
		stopSignal string
	)

	exposedPorts := make(map[string]struct{})
	volumes := make(map[string]struct{})
	labels := make(map[string]string)

	for _, ch := range changes {
		pair := strings.Split(ch, "=")
		if len(pair) == 1 {
			return v1.ImageConfig{}, errors.Errorf("no value given for instruction %q", ch)
		}
		switch pair[0] {
		case "USER":
			user = pair[1]
		case "EXPOSE":
			var st struct{}
			exposedPorts[pair[1]] = st
		case "ENV":
			env = append(env, pair[1])
		case "ENTRYPOINT":
			entrypoint = append(entrypoint, pair[1])
		case "CMD":
			cmd = append(cmd, pair[1])
		case "VOLUME":
			var st struct{}
			volumes[pair[1]] = st
		case "WORKDIR":
			workingDir = pair[1]
		case "LABEL":
			if len(pair) == 3 {
				labels[pair[1]] = pair[2]
			} else {
				labels[pair[1]] = ""
			}
		case "STOPSIGNAL":
			stopSignal = pair[1]
		}
	}

	return v1.ImageConfig{
		User:         user,
		ExposedPorts: exposedPorts,
		Env:          env,
		Entrypoint:   entrypoint,
		Cmd:          cmd,
		Volumes:      volumes,
		WorkingDir:   workingDir,
		Labels:       labels,
		StopSignal:   stopSignal,
	}, nil
}