Use new style ISO BIOS mkimage from Linuxkit which unpacks filesystem

Rather than using an initrd, unpack full filesystem for ISO BIOS.

Stream docker output direct to file rather than via a buffer, to save
memory.

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

src/moby/docker.go

@@ -21,48 +21,26 @@ import (
 	"golang.org/x/net/context"
 )
 
-func dockerRun(input io.Reader, args ...string) ([]byte, error) {
+func dockerRun(input io.Reader, output io.Writer, args ...string) error {
 	log.Debugf("docker run (input): %s", strings.Join(args, " "))
 	docker, err := exec.LookPath("docker")
 	if err != nil {
-		return []byte{}, errors.New("Docker does not seem to be installed")
+		return errors.New("Docker does not seem to be installed")
 	}
 	args = append([]string{"run", "--rm", "-i"}, args...)
 	cmd := exec.Command(docker, args...)
 	cmd.Stdin = input
+	cmd.Stdout = output
 
-	stderrPipe, err := cmd.StderrPipe()
+	if err := cmd.Run(); err != nil {
-	if err != nil {
+		if exitError, ok := err.(*exec.ExitError); ok {
-		return []byte{}, err
+			return fmt.Errorf("docker run failed: %v output:\n%s", err, exitError.Stderr)
 		}
-
+		return err
-	stdoutPipe, err := cmd.StdoutPipe()
-	if err != nil {
-		return []byte{}, err
-	}
-
-	err = cmd.Start()
-	if err != nil {
-		return []byte{}, err
-	}
-
-	stdout, err := ioutil.ReadAll(stdoutPipe)
-	if err != nil {
-		return []byte{}, err
-	}
-
-	stderr, err := ioutil.ReadAll(stderrPipe)
-	if err != nil {
-		return []byte{}, err
-	}
-
-	err = cmd.Wait()
-	if err != nil {
-		return []byte{}, fmt.Errorf("%v: %s", err, stderr)
 	}
 
 	log.Debugf("docker run (input): %s...Done", strings.Join(args, " "))
-	return stdout, nil
+	return nil
 }
 
 func dockerCreate(image string) (string, error) {

src/moby/output.go

@@ -12,7 +12,7 @@ import (
 )
 
 const (
-	bios       = "linuxkit/mkimage-iso-bios:db791abed6f2b5320feb6cec255a635aee3756f6@sha256:e57483075307bcea4a7257f87eee733d3e24e7a964ba15dcc01111df6729ab3b"
+	bios       = "linuxkit/mkimage-iso-bios:1140a4f96b04d6744160f6e3ae485bf7f7a945a8@sha256:878c7d7162120be1c388fded863eef28908b3ebf1c0751b78193103c10d4f6d1"
 	efi        = "linuxkit/mkimage-iso-efi:5c2fc616bde288476a14f4f6dd0d273a66832822@sha256:876ef47ec2b30af40e70f1e98f496206eb430915867c4f9f400e1af47fd58d7c"
 	gcp        = "linuxkit/mkimage-gcp:46716b3d3f7aa1a7607a3426fe0ccebc554b14ee@sha256:18d8e0482f65a2481f5b6ba1e7ce77723b246bf13bdb612be5e64df90297940c"
 	vhd        = "linuxkit/mkimage-vhd:a04c8480d41ca9cef6b7710bd45a592220c3acb2@sha256:ba373dc8ae5dc72685dbe4b872d8f588bc68b2114abd8bdc6a74d82a2b62cce3"
@@ -33,11 +33,7 @@ var outFuns = map[string]func(string, []byte, int, bool) error{
 		return nil
 	},
 	"iso-bios": func(base string, image []byte, size int, hyperkit bool) error {
-		kernel, initrd, cmdline, err := tarToInitrd(image)
+		err := outputIso(bios, base+".iso", image)
-		if err != nil {
-			return fmt.Errorf("Error converting to initrd: %v", err)
-		}
-		err = outputImg(bios, base+".iso", kernel, initrd, cmdline)
 		if err != nil {
 			return fmt.Errorf("Error writing iso-bios output: %v", err)
 		}
@@ -246,15 +242,12 @@ func outputImg(image, filename string, kernel []byte, initrd []byte, cmdline str
 	if err != nil {
 		return err
 	}
-	img, err := dockerRun(buf, image, cmdline)
+	output, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
-	err = ioutil.WriteFile(filename, img, os.FileMode(0644))
+	defer output.Close()
-	if err != nil {
+	return dockerRun(buf, output, image, cmdline)
-		return err
-	}
-	return nil
 }
 
 // this should replace the other version for types that can specify a size
@@ -265,20 +258,26 @@ func outputImgSize(image, filename string, kernel []byte, initrd []byte, cmdline
 	if err != nil {
 		return err
 	}
-	var img []byte
+	output, err := os.Create(filename)
+	if err != nil {
+		return err
+	}
+	defer output.Close()
 	if size == 0 {
-		img, err = dockerRun(buf, image)
+		return dockerRun(buf, output, image)
-	} else {
-		img, err = dockerRun(buf, image, fmt.Sprintf("%dM", size))
 	}
+	return dockerRun(buf, output, image, fmt.Sprintf("%dM", size))
+}
+
+func outputIso(image, filename string, filesystem []byte) error {
+	log.Debugf("output ISO: %s %s", image, filename)
+	log.Infof("  %s", filename)
+	output, err := os.Create(filename)
 	if err != nil {
 		return err
 	}
-	err = ioutil.WriteFile(filename, img, os.FileMode(0644))
+	defer output.Close()
-	if err != nil {
+	return dockerRun(bytes.NewBuffer(filesystem), output, image)
-		return err
-	}
-	return nil
 }
 
 func outputKernelInitrd(base string, kernel []byte, initrd []byte, cmdline string) error {