linuxkit/src/cmd/moby/build.go

package main

import (
	"archive/tar"
	"bytes"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"path/filepath"

	log "github.com/Sirupsen/logrus"
	"github.com/docker/moby/src/initrd"
)

func untarKernel(buf *bytes.Buffer, bzimageName, ktarName string) (*bytes.Buffer, *bytes.Buffer, error) {
	tr := tar.NewReader(buf)

	var bzimage, ktar *bytes.Buffer

	for {
		hdr, err := tr.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatalln(err)
		}
		switch hdr.Name {
		case bzimageName:
			bzimage = new(bytes.Buffer)
			_, err := io.Copy(bzimage, tr)
			if err != nil {
				return nil, nil, err
			}
		case ktarName:
			ktar = new(bytes.Buffer)
			_, err := io.Copy(bzimage, tr)
			if err != nil {
				return nil, nil, err
			}
		default:
			continue
		}
	}

	if ktar == nil || bzimage == nil {
		return nil, nil, errors.New("did not find bzImage and kernel.tar in tarball")
	}

	return bzimage, ktar, nil
}

func containersInitrd(containers []*bytes.Buffer) (*bytes.Buffer, error) {
	w := new(bytes.Buffer)
	iw := initrd.NewWriter(w)
	defer iw.Close()
	for _, file := range containers {
		_, err := initrd.Copy(iw, file)
		if err != nil {
			return nil, err
		}
	}

	return w, nil
}

func build(name string, pull bool, args []string) {
	conf := "moby.yml"
	if len(args) > 0 {
		conf = args[0]
	}

	if name == "" {
		name = filepath.Base(conf)
		ext := filepath.Ext(conf)
		if ext != "" {
			name = name[:len(name)-len(ext)]
		}
	}

	config, err := ioutil.ReadFile(conf)
	if err != nil {
		log.Fatalf("Cannot open config file: %v", err)
	}

	m, err := NewConfig(config)
	if err != nil {
		log.Fatalf("Invalid config: %v", err)
	}

	containers := []*bytes.Buffer{}

	if pull {
		err := dockerPull(m.Kernel.Image)
		if err != nil {
			log.Fatalf("Could not pull image %s: %v", m.Kernel.Image, err)
		}
	}
	// get kernel bzImage and initrd tarball from container
	// TODO examine contents to see what names they might have
	const (
		bzimageName = "bzImage"
		ktarName    = "kernel.tar"
	)
	out, err := dockerRun(m.Kernel.Image, "tar", "cf", "-", bzimageName, ktarName)
	if err != nil {
		log.Fatalf("Failed to extract kernel image and tarball: %v", err)
	}
	buf := bytes.NewBuffer(out)
	bzimage, ktar, err := untarKernel(buf, bzimageName, ktarName)
	if err != nil {
		log.Fatalf("Could not extract bzImage and kernel filesystem from tarball. %v", err)
	}
	containers = append(containers, ktar)

	// convert init image to tarball
	if pull {
		err := dockerPull(m.Init)
		if err != nil {
			log.Fatalf("Could not pull image %s: %v", m.Init, err)
		}
	}
	init, err := ImageExtract(m.Init, "")
	if err != nil {
		log.Fatalf("Failed to build init tarball: %v", err)
	}
	buffer := bytes.NewBuffer(init)
	containers = append(containers, buffer)

	for i, image := range m.System {
		if pull {
			err := dockerPull(image.Image)
			if err != nil {
				log.Fatalf("Could not pull image %s: %v", image.Image, err)
			}
		}
		config, err := ConfigToOCI(&image)
		if err != nil {
			log.Fatalf("Failed to run riddler to get config.json for %s: %v", image.Image, err)
		}
		so := fmt.Sprintf("%03d", i)
		path := "containers/system/" + so + "-" + image.Name
		out, err := ImageBundle(path, image.Image, config)
		if err != nil {
			log.Fatalf("Failed to extract root filesystem for %s: %v", image.Image, err)
		}
		buffer := bytes.NewBuffer(out)
		containers = append(containers, buffer)
	}

	for _, image := range m.Daemon {
		if pull {
			err := dockerPull(image.Image)
			if err != nil {
				log.Fatalf("Could not pull image %s: %v", image.Image, err)
			}
		}
		config, err := ConfigToOCI(&image)
		if err != nil {
			log.Fatalf("Failed to run riddler to get config.json for %s: %v", image.Image, err)
		}
		path := "containers/daemon/" + image.Name
		out, err := ImageBundle(path, image.Image, config)
		if err != nil {
			log.Fatalf("Failed to extract root filesystem for %s: %v", image.Image, err)
		}
		buffer := bytes.NewBuffer(out)
		containers = append(containers, buffer)
	}

	// add files
	buffer, err = filesystem(m)
	if err != nil {
		log.Fatalf("failed to add filesystem parts: %v", err)
	}
	containers = append(containers, buffer)

	initrd, err := containersInitrd(containers)
	if err != nil {
		log.Fatalf("Failed to make initrd %v", err)
	}

	err = outputs(m, name, bzimage.Bytes(), initrd.Bytes())
	if err != nil {
		log.Fatalf("Error writing outputs: %v", err)
	}
}