@@ -10,6 +10,7 @@ import (

 	"os"

 	"os/exec"

 	"path"

+	"strconv"

 	"strings"

 	"syscall"

@@ -21,6 +22,7 @@ import (

 	"github.com/docker/docker/pkg/directory"

 	"github.com/docker/docker/pkg/idtools"

 	"github.com/docker/docker/pkg/mount"

+	"github.com/docker/docker/pkg/parsers"

 	"github.com/docker/docker/pkg/parsers/kernel"

 	"github.com/opencontainers/runc/libcontainer/label"

@@ -92,6 +94,10 @@ func init() {

 // If overlay filesystem is not supported on the host, graphdriver.ErrNotSupported is returned as error.

 // If a overlay filesystem is not supported over a existing filesystem then error graphdriver.ErrIncompatibleFS is returned.

 func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (graphdriver.Driver, error) {

+	opts, err := parseOptions(options)

+	if err != nil {

+		return nil, err

+	}

 	if err := supportsOverlay(); err != nil {

 		return nil, graphdriver.ErrNotSupported

@@ -103,7 +109,10 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap

 		return nil, err

 	}

 	if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 {

-		return nil, graphdriver.ErrNotSupported

+		if !opts.overrideKernelCheck {

+			return nil, graphdriver.ErrNotSupported

+		}

+		logrus.Warnf("Using pre-4.0.0 kernel for overlay2, mount failures may require kernel update")

 	}

 	fsMagic, err := graphdriver.GetFSMagic(home)

@@ -144,6 +153,31 @@ func Init(home string, options []string, uidMaps, gidMaps []idtools.IDMap) (grap

 	return d, nil

 }

+type overlayOptions struct {

+	overrideKernelCheck bool

+}

+

+func parseOptions(options []string) (*overlayOptions, error) {

+	o := &overlayOptions{}

+	for _, option := range options {

+		key, val, err := parsers.ParseKeyValueOpt(option)

+		if err != nil {

+			return nil, err

+		}

+		key = strings.ToLower(key)

+		switch key {

+		case "overlay2.override_kernel_check":

+			o.overrideKernelCheck, err = strconv.ParseBool(val)

+			if err != nil {

+				return nil, err

+			}

+		default:

+			return nil, fmt.Errorf("overlay2: Unknown option %s\n", key)

+		}

+	}

+	return o, nil

+}

+

 func supportsOverlay() error {

 	// We can try to modprobe overlay first before looking at

 	// proc/filesystems for when overlay is supported

@@ -566,6 +566,17 @@ options for `zfs` start with `zfs` and options for `btrfs` start with `btrfs`.

     Example use:

         $ docker daemon -s btrfs --storage-opt btrfs.min_space=10G

+#### Overlay2 options

+

+* `overlay2.override_kernel_check`

+

+    Overrides the Linux kernel version check allowing overlay2. Support for

+    specifying multiple lower directories needed by overlay2 was added to the

+    Linux kernel in 4.0.0. However some older kernel versions may be patched

+    to add multiple lower directory support for OverlayFS. This option should

+    only be used after verifying this support exists in the kernel. Applying

+    this option on a kernel without this support will cause failures on mount.

+

 ## Docker runtime execution options

 The Docker daemon relies on a