moby/migrate/v1/migratev1_test.go

package v1

import (
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"testing"

	"github.com/docker/distribution/reference"
	"github.com/docker/docker/distribution/metadata"
	"github.com/docker/docker/image"
	"github.com/docker/docker/layer"
	"github.com/opencontainers/go-digest"
)

func TestMigrateRefs(t *testing.T) {
	tmpdir, err := ioutil.TempDir("", "migrate-tags")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmpdir)

	ioutil.WriteFile(filepath.Join(tmpdir, "repositories-generic"), []byte(`{"Repositories":{"busybox":{"latest":"b3ca410aa2c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108","sha256:16a2a52884c2a9481ed267c2d46483eac7693b813a63132368ab098a71303f8a":"b3ca410aa2c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108"},"registry":{"2":"5d165b8e4b203685301c815e95663231691d383fd5e3d3185d1ce3f8dddead3d","latest":"8d5547a9f329b1d3f93198cd661fb5117e5a96b721c5cf9a2c389e7dd4877128"}}}`), 0600)

	ta := &mockTagAdder{}
	err = migrateRefs(tmpdir, "generic", ta, map[string]image.ID{
		"5d165b8e4b203685301c815e95663231691d383fd5e3d3185d1ce3f8dddead3d": image.ID("sha256:2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"),
		"b3ca410aa2c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108": image.ID("sha256:fcde2b2edba56bf408601fb721fe9b5c338d10ee429ea04fae5511b68fbf8fb9"),
		"abcdef3434c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108": image.ID("sha256:56434342345ae68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae"),
	})
	if err != nil {
		t.Fatal(err)
	}

	expected := map[string]string{
		"docker.io/library/busybox:latest":                                                                  "sha256:fcde2b2edba56bf408601fb721fe9b5c338d10ee429ea04fae5511b68fbf8fb9",
		"docker.io/library/busybox@sha256:16a2a52884c2a9481ed267c2d46483eac7693b813a63132368ab098a71303f8a": "sha256:fcde2b2edba56bf408601fb721fe9b5c338d10ee429ea04fae5511b68fbf8fb9",
		"docker.io/library/registry:2":                                                                      "sha256:2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae",
	}

	if !reflect.DeepEqual(expected, ta.refs) {
		t.Fatalf("Invalid migrated tags: expected %q, got %q", expected, ta.refs)
	}

	// second migration is no-op
	ioutil.WriteFile(filepath.Join(tmpdir, "repositories-generic"), []byte(`{"Repositories":{"busybox":{"latest":"b3ca410aa2c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108"`), 0600)
	err = migrateRefs(tmpdir, "generic", ta, map[string]image.ID{
		"b3ca410aa2c115c05969a7b2c8cf8a9fcf62c1340ed6a601c9ee50df337ec108": image.ID("sha256:fcde2b2edba56bf408601fb721fe9b5c338d10ee429ea04fae5511b68fbf8fb9"),
	})
	if err != nil {
		t.Fatal(err)
	}
	if !reflect.DeepEqual(expected, ta.refs) {
		t.Fatalf("Invalid migrated tags: expected %q, got %q", expected, ta.refs)
	}
}

func TestMigrateContainers(t *testing.T) {
	// TODO Windows: Figure out why this is failing
	if runtime.GOOS == "windows" {
		t.Skip("Failing on Windows")
	}
	if runtime.GOARCH != "amd64" {
		t.Skip("Test tailored to amd64 architecture")
	}
	tmpdir, err := ioutil.TempDir("", "migrate-containers")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmpdir)

	err = addContainer(tmpdir, `{"State":{"Running":false,"Paused":false,"Restarting":false,"OOMKilled":false,"Dead":false,"Pid":0,"ExitCode":0,"Error":"","StartedAt":"2015-11-10T21:42:40.604267436Z","FinishedAt":"2015-11-10T21:42:41.869265487Z"},"ID":"f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c","Created":"2015-11-10T21:42:40.433831551Z","Path":"sh","Args":[],"Config":{"Hostname":"f780ee3f80e6","Domainname":"","User":"","AttachStdin":true,"AttachStdout":true,"AttachStderr":true,"Tty":true,"OpenStdin":true,"StdinOnce":true,"Env":null,"Cmd":["sh"],"Image":"busybox","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":{}},"Image":"2c5ac3f849df8627fcf2822727f87c57f38b7129d3604fbc11d861fe856ff093","NetworkSettings":{"Bridge":"","EndpointID":"","Gateway":"","GlobalIPv6Address":"","GlobalIPv6PrefixLen":0,"HairpinMode":false,"IPAddress":"","IPPrefixLen":0,"IPv6Gateway":"","LinkLocalIPv6Address":"","LinkLocalIPv6PrefixLen":0,"MacAddress":"","NetworkID":"","PortMapping":null,"Ports":null,"SandboxKey":"","SecondaryIPAddresses":null,"SecondaryIPv6Addresses":null},"ResolvConfPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/resolv.conf","HostnamePath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/hostname","HostsPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/hosts","LogPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c-json.log","Name":"/determined_euclid","Driver":"overlay","ExecDriver":"native-0.2","MountLabel":"","ProcessLabel":"","RestartCount":0,"UpdateDns":false,"HasBeenStartedBefore":false,"MountPoints":{},"Volumes":{},"VolumesRW":{},"AppArmorProfile":""}`)
	if err != nil {
		t.Fatal(err)
	}

	// container with invalid image
	err = addContainer(tmpdir, `{"State":{"Running":false,"Paused":false,"Restarting":false,"OOMKilled":false,"Dead":false,"Pid":0,"ExitCode":0,"Error":"","StartedAt":"2015-11-10T21:42:40.604267436Z","FinishedAt":"2015-11-10T21:42:41.869265487Z"},"ID":"e780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c","Created":"2015-11-10T21:42:40.433831551Z","Path":"sh","Args":[],"Config":{"Hostname":"f780ee3f80e6","Domainname":"","User":"","AttachStdin":true,"AttachStdout":true,"AttachStderr":true,"Tty":true,"OpenStdin":true,"StdinOnce":true,"Env":null,"Cmd":["sh"],"Image":"busybox","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":{}},"Image":"4c5ac3f849df8627fcf2822727f87c57f38b7129d3604fbc11d861fe856ff093","NetworkSettings":{"Bridge":"","EndpointID":"","Gateway":"","GlobalIPv6Address":"","GlobalIPv6PrefixLen":0,"HairpinMode":false,"IPAddress":"","IPPrefixLen":0,"IPv6Gateway":"","LinkLocalIPv6Address":"","LinkLocalIPv6PrefixLen":0,"MacAddress":"","NetworkID":"","PortMapping":null,"Ports":null,"SandboxKey":"","SecondaryIPAddresses":null,"SecondaryIPv6Addresses":null},"ResolvConfPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/resolv.conf","HostnamePath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/hostname","HostsPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/hosts","LogPath":"/var/lib/docker/containers/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c/f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c-json.log","Name":"/determined_euclid","Driver":"overlay","ExecDriver":"native-0.2","MountLabel":"","ProcessLabel":"","RestartCount":0,"UpdateDns":false,"HasBeenStartedBefore":false,"MountPoints":{},"Volumes":{},"VolumesRW":{},"AppArmorProfile":""}`)
	if err != nil {
		t.Fatal(err)
	}

	ls := &mockMounter{}

	ifs, err := image.NewFSStoreBackend(filepath.Join(tmpdir, "imagedb"))
	if err != nil {
		t.Fatal(err)
	}

	is, err := image.NewImageStore(ifs, ls)
	if err != nil {
		t.Fatal(err)
	}

	imgID, err := is.Create([]byte(`{"architecture":"amd64","config":{"AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Cmd":["sh"],"Entrypoint":null,"Env":null,"Hostname":"23304fc829f9","Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Labels":null,"OnBuild":null,"OpenStdin":false,"StdinOnce":false,"Tty":false,"Volumes":null,"WorkingDir":"","Domainname":"","User":""},"container":"349b014153779e30093d94f6df2a43c7a0a164e05aa207389917b540add39b51","container_config":{"AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Cmd":["/bin/sh","-c","#(nop) CMD [\"sh\"]"],"Entrypoint":null,"Env":null,"Hostname":"23304fc829f9","Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Labels":null,"OnBuild":null,"OpenStdin":false,"StdinOnce":false,"Tty":false,"Volumes":null,"WorkingDir":"","Domainname":"","User":""},"created":"2015-10-31T22:22:55.613815829Z","docker_version":"1.8.2","history":[{"created":"2015-10-31T22:22:54.690851953Z","created_by":"/bin/sh -c #(nop) ADD file:a3bc1e842b69636f9df5256c49c5374fb4eef1e281fe3f282c65fb853ee171c5 in /"},{"created":"2015-10-31T22:22:55.613815829Z","created_by":"/bin/sh -c #(nop) CMD [\"sh\"]"}],"os":"linux","rootfs":{"type":"layers","diff_ids":["sha256:c6f988f4874bb0add23a778f753c65efe992244e148a1d2ec2a8b664fb66bbd1","sha256:5f70bf18a086007016e948b04aed3b82103a36bea41755b6cddfaf10ace3c6ef"]}}`))
	if err != nil {
		t.Fatal(err)
	}

	err = migrateContainers(tmpdir, ls, is, map[string]image.ID{
		"2c5ac3f849df8627fcf2822727f87c57f38b7129d3604fbc11d861fe856ff093": imgID,
	})
	if err != nil {
		t.Fatal(err)
	}

	expected := []mountInfo{{
		"f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c",
		"f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c",
		"sha256:c3191d32a37d7159b2e30830937d2e30268ad6c375a773a8994911a3aba9b93f",
	}}
	if !reflect.DeepEqual(expected, ls.mounts) {
		t.Fatalf("invalid mounts: expected %q, got %q", expected, ls.mounts)
	}

	if actual, expected := ls.count, 0; actual != expected {
		t.Fatalf("invalid active mounts: expected %d, got %d", expected, actual)
	}

	config2, err := ioutil.ReadFile(filepath.Join(tmpdir, "containers", "f780ee3f80e66e9b432a57049597118a66aab8932be88e5628d4c824edbee37c", "config.v2.json"))
	if err != nil {
		t.Fatal(err)
	}
	var config struct{ Image string }
	err = json.Unmarshal(config2, &config)
	if err != nil {
		t.Fatal(err)
	}

	if actual, expected := config.Image, string(imgID); actual != expected {
		t.Fatalf("invalid image pointer in migrated config: expected %q, got %q", expected, actual)
	}

}

func TestMigrateImages(t *testing.T) {
	// TODO Windows: Figure out why this is failing
	if runtime.GOOS == "windows" {
		t.Skip("Failing on Windows")
	}
	if runtime.GOARCH != "amd64" {
		t.Skip("Test tailored to amd64 architecture")
	}
	tmpdir, err := ioutil.TempDir("", "migrate-images")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmpdir)

	// busybox from 1.9
	id1, err := addImage(tmpdir, `{"architecture":"amd64","config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Image":"","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null},"container":"23304fc829f9b9349416f6eb1afec162907eba3a328f51d53a17f8986f865d65","container_config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["/bin/sh","-c","#(nop) ADD file:a3bc1e842b69636f9df5256c49c5374fb4eef1e281fe3f282c65fb853ee171c5 in /"],"Image":"","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null},"created":"2015-10-31T22:22:54.690851953Z","docker_version":"1.8.2","layer_id":"sha256:55dc925c23d1ed82551fd018c27ac3ee731377b6bad3963a2a4e76e753d70e57","os":"linux"}`, "", "")
	if err != nil {
		t.Fatal(err)
	}

	id2, err := addImage(tmpdir, `{"architecture":"amd64","config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["sh"],"Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null},"container":"349b014153779e30093d94f6df2a43c7a0a164e05aa207389917b540add39b51","container_config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["/bin/sh","-c","#(nop) CMD [\"sh\"]"],"Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Volumes":null,"WorkingDir":"","Entrypoint":null,"OnBuild":null,"Labels":null},"created":"2015-10-31T22:22:55.613815829Z","docker_version":"1.8.2","layer_id":"sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4","os":"linux","parent_id":"sha256:039b63dd2cbaa10d6015ea574392530571ed8d7b174090f032211285a71881d0"}`, id1, "")
	if err != nil {
		t.Fatal(err)
	}

	ls := &mockRegistrar{}

	ifs, err := image.NewFSStoreBackend(filepath.Join(tmpdir, "imagedb"))
	if err != nil {
		t.Fatal(err)
	}

	is, err := image.NewImageStore(ifs, ls)
	if err != nil {
		t.Fatal(err)
	}

	ms, err := metadata.NewFSMetadataStore(filepath.Join(tmpdir, "distribution"))
	if err != nil {
		t.Fatal(err)
	}
	mappings := make(map[string]image.ID)

	err = migrateImages(tmpdir, ls, is, ms, mappings)
	if err != nil {
		t.Fatal(err)
	}

	expected := map[string]image.ID{
		id1: image.ID("sha256:ca406eaf9c26898414ff5b7b3a023c33310759d6203be0663dbf1b3a712f432d"),
		id2: image.ID("sha256:a488bec94bb96b26a968f913d25ef7d8d204d727ca328b52b4b059c7d03260b6"),
	}

	if !reflect.DeepEqual(mappings, expected) {
		t.Fatalf("invalid image mappings: expected %q, got %q", expected, mappings)
	}

	if actual, expected := ls.count, 2; actual != expected {
		t.Fatalf("invalid register count: expected %q, got %q", expected, actual)
	}
	ls.count = 0

	// next images are busybox from 1.8.2
	_, err = addImage(tmpdir, `{"id":"17583c7dd0dae6244203b8029733bdb7d17fccbb2b5d93e2b24cf48b8bfd06e2","parent":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","created":"2015-10-31T22:22:55.613815829Z","container":"349b014153779e30093d94f6df2a43c7a0a164e05aa207389917b540add39b51","container_config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"ExposedPorts":null,"PublishService":"","Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["/bin/sh","-c","#(nop) CMD [\"sh\"]"],"Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Volumes":null,"VolumeDriver":"","WorkingDir":"","Entrypoint":null,"NetworkDisabled":false,"MacAddress":"","OnBuild":null,"Labels":null},"docker_version":"1.8.2","config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"ExposedPorts":null,"PublishService":"","Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["sh"],"Image":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","Volumes":null,"VolumeDriver":"","WorkingDir":"","Entrypoint":null,"NetworkDisabled":false,"MacAddress":"","OnBuild":null,"Labels":null},"architecture":"amd64","os":"linux","Size":0}`, "", "sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4")
	if err != nil {
		t.Fatal(err)
	}

	_, err = addImage(tmpdir, `{"id":"d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498","created":"2015-10-31T22:22:54.690851953Z","container":"23304fc829f9b9349416f6eb1afec162907eba3a328f51d53a17f8986f865d65","container_config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"ExposedPorts":null,"PublishService":"","Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":["/bin/sh","-c","#(nop) ADD file:a3bc1e842b69636f9df5256c49c5374fb4eef1e281fe3f282c65fb853ee171c5 in /"],"Image":"","Volumes":null,"VolumeDriver":"","WorkingDir":"","Entrypoint":null,"NetworkDisabled":false,"MacAddress":"","OnBuild":null,"Labels":null},"docker_version":"1.8.2","config":{"Hostname":"23304fc829f9","Domainname":"","User":"","AttachStdin":false,"AttachStdout":false,"AttachStderr":false,"ExposedPorts":null,"PublishService":"","Tty":false,"OpenStdin":false,"StdinOnce":false,"Env":null,"Cmd":null,"Image":"","Volumes":null,"VolumeDriver":"","WorkingDir":"","Entrypoint":null,"NetworkDisabled":false,"MacAddress":"","OnBuild":null,"Labels":null},"architecture":"amd64","os":"linux","Size":1108935}`, "", "sha256:55dc925c23d1ed82551fd018c27ac3ee731377b6bad3963a2a4e76e753d70e57")
	if err != nil {
		t.Fatal(err)
	}

	err = migrateImages(tmpdir, ls, is, ms, mappings)
	if err != nil {
		t.Fatal(err)
	}

	expected["d1592a710ac323612bd786fa8ac20727c58d8a67847e5a65177c594f43919498"] = image.ID("sha256:c091bb33854e57e6902b74c08719856d30b5593c7db6143b2b48376b8a588395")
	expected["17583c7dd0dae6244203b8029733bdb7d17fccbb2b5d93e2b24cf48b8bfd06e2"] = image.ID("sha256:d963020e755ff2715b936065949472c1f8a6300144b922992a1a421999e71f07")

	if actual, expected := ls.count, 2; actual != expected {
		t.Fatalf("invalid register count: expected %q, got %q", expected, actual)
	}

	v2MetadataService := metadata.NewV2MetadataService(ms)
	receivedMetadata, err := v2MetadataService.GetMetadata(layer.EmptyLayer.DiffID())
	if err != nil {
		t.Fatal(err)
	}

	expectedMetadata := []metadata.V2Metadata{
		{Digest: digest.Digest("sha256:55dc925c23d1ed82551fd018c27ac3ee731377b6bad3963a2a4e76e753d70e57")},
		{Digest: digest.Digest("sha256:a3ed95caeb02ffe68cdd9fd84406680ae93d633cb16422d00e8a7c22955b46d4")},
	}

	if !reflect.DeepEqual(expectedMetadata, receivedMetadata) {
		t.Fatalf("invalid metadata: expected %q, got %q", expectedMetadata, receivedMetadata)
	}

}

func TestMigrateUnsupported(t *testing.T) {
	tmpdir, err := ioutil.TempDir("", "migrate-empty")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmpdir)

	err = os.MkdirAll(filepath.Join(tmpdir, "graph"), 0700)
	if err != nil {
		t.Fatal(err)
	}

	err = Migrate(tmpdir, "generic", nil, nil, nil, nil)
	if err != errUnsupported {
		t.Fatalf("expected unsupported error, got %q", err)
	}
}

func TestMigrateEmptyDir(t *testing.T) {
	tmpdir, err := ioutil.TempDir("", "migrate-empty")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(tmpdir)

	err = Migrate(tmpdir, "generic", nil, nil, nil, nil)
	if err != nil {
		t.Fatal(err)
	}
}

func addImage(dest, jsonConfig, parent, checksum string) (string, error) {
	var config struct{ ID string }
	if err := json.Unmarshal([]byte(jsonConfig), &config); err != nil {
		return "", err
	}
	if config.ID == "" {
		b := make([]byte, 32)
		rand.Read(b)
		config.ID = hex.EncodeToString(b)
	}
	contDir := filepath.Join(dest, "graph", config.ID)
	if err := os.MkdirAll(contDir, 0700); err != nil {
		return "", err
	}
	if err := ioutil.WriteFile(filepath.Join(contDir, "json"), []byte(jsonConfig), 0600); err != nil {
		return "", err
	}
	if checksum != "" {
		if err := ioutil.WriteFile(filepath.Join(contDir, "checksum"), []byte(checksum), 0600); err != nil {
			return "", err
		}
	}
	if err := ioutil.WriteFile(filepath.Join(contDir, ".migration-diffid"), []byte(layer.EmptyLayer.DiffID()), 0600); err != nil {
		return "", err
	}
	if err := ioutil.WriteFile(filepath.Join(contDir, ".migration-size"), []byte("0"), 0600); err != nil {
		return "", err
	}
	if parent != "" {
		if err := ioutil.WriteFile(filepath.Join(contDir, "parent"), []byte(parent), 0600); err != nil {
			return "", err
		}
	}
	if checksum != "" {
		if err := ioutil.WriteFile(filepath.Join(contDir, "checksum"), []byte(checksum), 0600); err != nil {
			return "", err
		}
	}
	return config.ID, nil
}

func addContainer(dest, jsonConfig string) error {
	var config struct{ ID string }
	if err := json.Unmarshal([]byte(jsonConfig), &config); err != nil {
		return err
	}
	contDir := filepath.Join(dest, "containers", config.ID)
	if err := os.MkdirAll(contDir, 0700); err != nil {
		return err
	}
	if err := ioutil.WriteFile(filepath.Join(contDir, "config.json"), []byte(jsonConfig), 0600); err != nil {
		return err
	}
	return nil
}

type mockTagAdder struct {
	refs map[string]string
}

func (t *mockTagAdder) AddTag(ref reference.Named, id digest.Digest, force bool) error {
	if t.refs == nil {
		t.refs = make(map[string]string)
	}
	t.refs[ref.String()] = id.String()
	return nil
}
func (t *mockTagAdder) AddDigest(ref reference.Canonical, id digest.Digest, force bool) error {
	return t.AddTag(ref, id, force)
}

type mockRegistrar struct {
	layers map[layer.ChainID]*mockLayer
	count  int
}

func (r *mockRegistrar) RegisterByGraphID(graphID string, parent layer.ChainID, diffID layer.DiffID, tarDataFile string, size int64) (layer.Layer, error) {
	r.count++
	l := &mockLayer{}
	if parent != "" {
		p, exists := r.layers[parent]
		if !exists {
			return nil, fmt.Errorf("invalid parent %q", parent)
		}
		l.parent = p
		l.diffIDs = append(l.diffIDs, p.diffIDs...)
	}
	l.diffIDs = append(l.diffIDs, diffID)
	if r.layers == nil {
		r.layers = make(map[layer.ChainID]*mockLayer)
	}
	r.layers[l.ChainID()] = l
	return l, nil
}
func (r *mockRegistrar) Release(l layer.Layer) ([]layer.Metadata, error) {
	return nil, nil
}
func (r *mockRegistrar) Get(layer.ChainID) (layer.Layer, error) {
	return nil, nil
}

type mountInfo struct {
	name, graphID, parent string
}
type mockMounter struct {
	mounts []mountInfo
	count  int
}

func (r *mockMounter) CreateRWLayerByGraphID(name string, graphID string, parent layer.ChainID) error {
	r.mounts = append(r.mounts, mountInfo{name, graphID, string(parent)})
	return nil
}
func (r *mockMounter) Unmount(string) error {
	r.count--
	return nil
}
func (r *mockMounter) Get(layer.ChainID) (layer.Layer, error) {
	return nil, nil
}

func (r *mockMounter) Release(layer.Layer) ([]layer.Metadata, error) {
	return nil, nil
}

type mockLayer struct {
	diffIDs []layer.DiffID
	parent  *mockLayer
}

func (l *mockLayer) TarStream() (io.ReadCloser, error) {
	return nil, nil
}
func (l *mockLayer) TarStreamFrom(layer.ChainID) (io.ReadCloser, error) {
	return nil, nil
}

func (l *mockLayer) ChainID() layer.ChainID {
	return layer.CreateChainID(l.diffIDs)
}

func (l *mockLayer) DiffID() layer.DiffID {
	return l.diffIDs[len(l.diffIDs)-1]
}

func (l *mockLayer) Parent() layer.Layer {
	if l.parent == nil {
		return nil
	}
	return l.parent
}

func (l *mockLayer) Size() (int64, error) {
	return 0, nil
}

func (l *mockLayer) DiffSize() (int64, error) {
	return 0, nil
}

func (l *mockLayer) Metadata() (map[string]string, error) {
	return nil, nil
}