@@ -228,7 +228,7 @@ func (d *dispatchRequest) getOsFromFlagsAndStage(stageOS string) string {

 		// multi-arch aware yet, it is guaranteed to only hold the OS part here.

 		return d.builder.options.Platform

 	default:

-		return runtime.GOOS

+		return "" // Auto-select

 	}

 }

@@ -247,9 +247,9 @@ func (d *dispatchRequest) getImageOrStage(name string, stageOS string) (builder.

 		imageImage.OS = runtime.GOOS

 		if runtime.GOOS == "windows" {

 			switch os {

-			case "windows", "":

+			case "windows":

 				return nil, errors.New("Windows does not support FROM scratch")

-			case "linux":

+			case "linux", "":

 				if !system.LCOWSupported() {

 					return nil, errors.New("Linux containers are not supported on this system")

 				}

@@ -166,7 +166,7 @@ func (i *ImageService) pullForBuilder(ctx context.Context, name string, authConf

 // Every call to GetImageAndReleasableLayer MUST call releasableLayer.Release() to prevent

 // leaking of layers.

 func (i *ImageService) GetImageAndReleasableLayer(ctx context.Context, refOrID string, opts backend.GetImageAndLayerOptions) (builder.Image, builder.ROLayer, error) {

-	if refOrID == "" {

+	if refOrID == "" { // ie FROM scratch

 		if !system.IsOSSupported(opts.OS) {

 			return nil, nil, system.ErrNotSupportedOperatingSystem

 		}

@@ -3,7 +3,6 @@ package images // import "github.com/docker/docker/daemon/images"

 import (

 	"context"

 	"io"

-	"runtime"

 	"strings"

 	"time"

@@ -65,11 +64,6 @@ func (i *ImageService) pullImageWithReference(ctx context.Context, ref reference

 		close(writesDone)

 	}()

-	// Default to the host OS platform in case it hasn't been populated with an explicit value.

-	if os == "" {

-		os = runtime.GOOS

-	}

-

 	imagePullConfig := &distribution.ImagePullConfig{

 		Config: distribution.Config{

 			MetaHeaders:      metaHeaders,

@@ -3,7 +3,6 @@ package distribution // import "github.com/docker/docker/distribution"

 import (

 	"context"

 	"fmt"

-	"runtime"

 	"github.com/docker/distribution/reference"

 	"github.com/docker/docker/api"

@@ -115,11 +114,6 @@ func Pull(ctx context.Context, ref reference.Named, imagePullConfig *ImagePullCo

 			continue

 		}

-		// Make sure we default the OS if it hasn't been supplied

-		if imagePullConfig.OS == "" {

-			imagePullConfig.OS = runtime.GOOS

-		}

-

 		if err := puller.Pull(ctx, ref, imagePullConfig.OS); err != nil {

 			// Was this pull cancelled? If so, don't try to fall

 			// back.

@@ -509,6 +509,14 @@ func (p *v2Puller) pullSchema1(ctx context.Context, ref reference.Reference, unv

 		}

 	}

+	// In the situation that the API call didn't specify an OS explicitly, but

+	// we support the operating system, switch to that operating system.

+	// eg FROM supertest2014/nyan with no platform specifier, and docker build

+	// with no --platform= flag under LCOW.

+	if requestedOS == "" && system.IsOSSupported(configOS) {

+		requestedOS = configOS

+	}

+

 	// Early bath if the requested OS doesn't match that of the configuration.

 	// This avoids doing the download, only to potentially fail later.

 	if !strings.EqualFold(configOS, requestedOS) {

@@ -618,9 +626,10 @@ func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *s

 		// Early bath if the requested OS doesn't match that of the configuration.

 		// This avoids doing the download, only to potentially fail later.

-		if !strings.EqualFold(configPlatform.OS, requestedOS) {

+		if !system.IsOSSupported(configPlatform.OS) {

 			return "", "", fmt.Errorf("cannot download image with operating system %q when requesting %q", configPlatform.OS, requestedOS)

 		}

+		requestedOS = configPlatform.OS

 		// Populate diff ids in descriptors to avoid downloading foreign layers

 		// which have been side loaded

@@ -629,6 +638,10 @@ func (p *v2Puller) pullSchema2(ctx context.Context, ref reference.Named, mfst *s

 		}

 	}

+	if requestedOS == "" {

+		requestedOS = runtime.GOOS

+	}

+

 	if p.config.DownloadManager != nil {

 		go func() {

 			var (

@@ -722,18 +735,22 @@ func receiveConfig(s ImageConfigStore, configChan <-chan []byte, errChan <-chan

 // pullManifestList handles "manifest lists" which point to various

 // platform-specific manifests.

-func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mfstList *manifestlist.DeserializedManifestList, os string) (id digest.Digest, manifestListDigest digest.Digest, err error) {

+func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mfstList *manifestlist.DeserializedManifestList, requestedOS string) (id digest.Digest, manifestListDigest digest.Digest, err error) {

 	manifestListDigest, err = schema2ManifestDigest(ref, mfstList)

 	if err != nil {

 		return "", "", err

 	}

-	logrus.Debugf("%s resolved to a manifestList object with %d entries; looking for a %s/%s match", ref, len(mfstList.Manifests), os, runtime.GOARCH)

+	logOS := requestedOS // May be "" indicating any OS

+	if logOS == "" {

+		logOS = "*"

+	}

+	logrus.Debugf("%s resolved to a manifestList object with %d entries; looking for a %s/%s match", ref, len(mfstList.Manifests), logOS, runtime.GOARCH)

-	manifestMatches := filterManifests(mfstList.Manifests, os)

+	manifestMatches := filterManifests(mfstList.Manifests, requestedOS)

 	if len(manifestMatches) == 0 {

-		errMsg := fmt.Sprintf("no matching manifest for %s/%s in the manifest list entries", os, runtime.GOARCH)

+		errMsg := fmt.Sprintf("no matching manifest for %s/%s in the manifest list entries", logOS, runtime.GOARCH)

 		logrus.Debugf(errMsg)

 		return "", "", errors.New(errMsg)

 	}

@@ -764,12 +781,12 @@ func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mf

 	switch v := manifest.(type) {

 	case *schema1.SignedManifest:

-		id, _, err = p.pullSchema1(ctx, manifestRef, v, os)

+		id, _, err = p.pullSchema1(ctx, manifestRef, v, manifestMatches[0].Platform.OS)

 		if err != nil {

 			return "", "", err

 		}

 	case *schema2.DeserializedManifest:

-		id, _, err = p.pullSchema2(ctx, manifestRef, v, os)

+		id, _, err = p.pullSchema2(ctx, manifestRef, v, manifestMatches[0].Platform.OS)

 		if err != nil {

 			return "", "", err

 		}

@@ -16,13 +16,13 @@ func (ld *v2LayerDescriptor) open(ctx context.Context) (distribution.ReadSeekClo

 	return blobs.Open(ctx, ld.digest)

 }

-func filterManifests(manifests []manifestlist.ManifestDescriptor, os string) []manifestlist.ManifestDescriptor {

+func filterManifests(manifests []manifestlist.ManifestDescriptor, _ string) []manifestlist.ManifestDescriptor {

 	var matches []manifestlist.ManifestDescriptor

 	for _, manifestDescriptor := range manifests {

-		if manifestDescriptor.Platform.Architecture == runtime.GOARCH && manifestDescriptor.Platform.OS == os {

+		if manifestDescriptor.Platform.Architecture == runtime.GOARCH && manifestDescriptor.Platform.OS == runtime.GOOS {

 			matches = append(matches, manifestDescriptor)

-			logrus.Debugf("found match for %s/%s with media type %s, digest %s", os, runtime.GOARCH, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

+			logrus.Debugf("found match for %s/%s with media type %s, digest %s", runtime.GOOS, runtime.GOARCH, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

 		}

 	}

 	return matches

@@ -62,24 +62,27 @@ func (ld *v2LayerDescriptor) open(ctx context.Context) (distribution.ReadSeekClo

 	return rsc, err

 }

-func filterManifests(manifests []manifestlist.ManifestDescriptor, os string) []manifestlist.ManifestDescriptor {

-	osVersion := ""

-	if os == "windows" {

-		version := system.GetOSVersion()

-		osVersion = fmt.Sprintf("%d.%d.%d", version.MajorVersion, version.MinorVersion, version.Build)

-		logrus.Debugf("will prefer entries with version %s", osVersion)

-	}

+func filterManifests(manifests []manifestlist.ManifestDescriptor, requestedOS string) []manifestlist.ManifestDescriptor {

+	version := system.GetOSVersion()

+	osVersion := fmt.Sprintf("%d.%d.%d", version.MajorVersion, version.MinorVersion, version.Build)

+	logrus.Debugf("will prefer Windows entries with version %s", osVersion)

 	var matches []manifestlist.ManifestDescriptor

+	foundWindowsMatch := false

 	for _, manifestDescriptor := range manifests {

-		if manifestDescriptor.Platform.Architecture == runtime.GOARCH && manifestDescriptor.Platform.OS == os {

+		if (manifestDescriptor.Platform.Architecture == runtime.GOARCH) &&

+			((requestedOS != "" && manifestDescriptor.Platform.OS == requestedOS) || // Explicit user request for an OS we know we support

+				(requestedOS == "" && system.IsOSSupported(manifestDescriptor.Platform.OS))) { // No user requested OS, but one we can support

 			matches = append(matches, manifestDescriptor)

-			logrus.Debugf("found match for %s/%s %s with media type %s, digest %s", os, runtime.GOARCH, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

+			logrus.Debugf("found match %s/%s %s with media type %s, digest %s", manifestDescriptor.Platform.OS, runtime.GOARCH, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

+			if strings.EqualFold("windows", manifestDescriptor.Platform.OS) {

+				foundWindowsMatch = true

+			}

 		} else {

-			logrus.Debugf("ignoring %s/%s %s with media type %s, digest %s", os, runtime.GOARCH, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

+			logrus.Debugf("ignoring %s/%s %s with media type %s, digest %s", manifestDescriptor.Platform.OS, manifestDescriptor.Platform.Architecture, manifestDescriptor.Platform.OSVersion, manifestDescriptor.MediaType, manifestDescriptor.Digest.String())

 		}

 	}

-	if os == "windows" {

+	if foundWindowsMatch {

 		sort.Stable(manifestsByVersion{osVersion, matches})

 	}

 	return matches

@@ -76,7 +76,8 @@ func (is *store) restore() error {

 		var l layer.Layer

 		if chainID := img.RootFS.ChainID(); chainID != "" {

 			if !system.IsOSSupported(img.OperatingSystem()) {

-				return system.ErrNotSupportedOperatingSystem

+				logrus.Errorf("not restoring image with unsupported operating system %v, %v, %s", dgst, chainID, img.OperatingSystem())

+				return nil

 			}

 			l, err = is.lss[img.OperatingSystem()].Get(chainID)

 			if err != nil {

@@ -59,10 +59,10 @@ func ParsePlatform(in string) *specs.Platform {

 // IsOSSupported determines if an operating system is supported by the host

 func IsOSSupported(os string) bool {

-	if runtime.GOOS == os {

+	if strings.EqualFold(runtime.GOOS, os) {

 		return true

 	}

-	if LCOWSupported() && os == "linux" {

+	if LCOWSupported() && strings.EqualFold(os, "linux") {

 		return true

 	}

 	return false