// Init returns the a native diff driver for overlay filesystem.
// 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
	}

	// require kernel 4.0.0 to ensure multiple lower dirs are supported
	v, err := kernel.GetKernelVersion()
	if err != nil {
		return nil, err
	}
	if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 {
		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)
	if err != nil {
		return nil, err
	}
	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
		backingFs = fsName
	}

	// check if they are running over btrfs, aufs, zfs, overlay, or ecryptfs
	switch fsMagic {
	case graphdriver.FsMagicBtrfs, graphdriver.FsMagicAufs, graphdriver.FsMagicZfs, graphdriver.FsMagicOverlay, graphdriver.FsMagicEcryptfs:
		logrus.Errorf("'overlay2' is not supported over %s", backingFs)
		return nil, graphdriver.ErrIncompatibleFS
	}

	rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
	if err != nil {
		return nil, err
	}
	// Create the driver home dir
	if err := idtools.MkdirAllAs(path.Join(home, linkDir), 0700, rootUID, rootGID); err != nil && !os.IsExist(err) {
		return nil, err
	}

	if err := mount.MakePrivate(home); err != nil {
		return nil, err
	}

	d := &Driver{
		home:    home,
		uidMaps: uidMaps,
		gidMaps: gidMaps,
		ctr:     graphdriver.NewRefCounter(graphdriver.NewFsChecker(graphdriver.FsMagicOverlay)),
	}

	return d, nil
}

func checkKernelVersion(k, major, minor int) bool {
	if v, err := kernel.GetKernelVersion(); err != nil {
		logrus.Warnf("%s", err)
	} else {
		if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: k, Major: major, Minor: minor}) < 0 {
			return false
		}
	}
	return true
}

func overlay2Supported() bool {
	if !overlayFSSupported() {
		return false
	}

	daemonV, err := kernel.ParseRelease(daemonKernelVersion)
	if err != nil {
		return false
	}
	requiredV := kernel.VersionInfo{Kernel: 4}
	return kernel.CompareKernelVersion(*daemonV, requiredV) > -1

}

func checkKernel(k, major, minor int) error {
	leastVersionInfo := kernel.VersionInfo{
		Kernel: k,
		Major:  major,
		Minor:  minor,
	}

	if v, err := kernel.GetKernelVersion(); err != nil {
		return err
	} else {
		if kernel.CompareKernelVersion(*v, leastVersionInfo) < 0 {
			msg := fmt.Sprintf("Your Linux kernel(%d.%d.%d) is too old to support Hyper daemon(%d.%d.%d+)",
				v.Kernel, v.Major, v.Minor, k, major, minor)
			return fmt.Errorf(msg)
		}
		return nil
	}
}

func checkSystem() error {
	// check OS version for compatibility, ensure running in global zone
	var err error
	var id C.zoneid_t

	if id, err = C.getzoneid(); err != nil {
		return fmt.Errorf("Exiting. Error getting zone id: %+v", err)
	}
	if int(id) != 0 {
		return fmt.Errorf("Exiting because the Docker daemon is not running in the global zone")
	}

	v, err := kernel.GetKernelVersion()
	if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 5, Major: 12, Minor: 0}) < 0 {
		return fmt.Errorf("Your Solaris kernel version: %s doesn't support Docker. Please upgrade to 5.12.0", v.String())
	}
	return err
}

func checkKernel() error {
	// Check for unsupported kernel versions
	// FIXME: it would be cleaner to not test for specific versions, but rather
	// test for specific functionalities.
	// Unfortunately we can't test for the feature "does not cause a kernel panic"
	// without actually causing a kernel panic, so we need this workaround until
	// the circumstances of pre-3.10 crashes are clearer.
	// For details see https://github.com/docker/docker/issues/407
	if k, err := kernel.GetKernelVersion(); err != nil {
		logrus.Warnf("%s", err)
	} else {
		if kernel.CompareKernelVersion(k, &kernel.KernelVersionInfo{Kernel: 3, Major: 10, Minor: 0}) < 0 {
			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
				logrus.Warnf("You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.10.0.", k.String())
			}
		}
	}
	return nil
}

func checkKernelAndArch() error {
	// Check for unsupported architectures
	if runtime.GOARCH != "amd64" {
		return fmt.Errorf("The Docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
	}
	// Check for unsupported kernel versions
	// FIXME: it would be cleaner to not test for specific versions, but rather
	// test for specific functionalities.
	// Unfortunately we can't test for the feature "does not cause a kernel panic"
	// without actually causing a kernel panic, so we need this workaround until
	// the circumstances of pre-3.8 crashes are clearer.
	// For details see http://github.com/docker/docker/issues/407
	if k, err := kernel.GetKernelVersion(); err != nil {
		log.Infof("WARNING: %s", err)
	} else {
		if kernel.CompareKernelVersion(k, &kernel.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
			if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
				log.Infof("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
			}
		}
	}
	return nil
}

			cmd := exec.Command(dockerBinary, "run", "--rm", "busybox", "/bin/sh", "-c", "cat /proc/filesystems")
			out, err := cmd.CombinedOutput()
			if err != nil {
				return false
			}
			return bytes.Contains(out, []byte("overlay\n"))
		},
		"Test cannot be run without suppport for overlayfs",
	}
	overlay2Supported = testRequirement{
		func() bool {
			if !overlayFSSupported.Condition() {
				return false
			}

			daemonV, err := kernel.ParseRelease(daemonKernelVersion)
			if err != nil {
				return false
			}
			requiredV := kernel.VersionInfo{Kernel: 4}
			return kernel.CompareKernelVersion(*daemonV, requiredV) > -1

		},
		"Test cannot be run without overlay2 support (kernel 4.0+)",
	}
)

func init() {
	SysInfo = sysinfo.New(true)
}

// Init returns the a native diff driver for overlay filesystem.
// If overlay filesystem is not supported on the host, graphdriver.ErrNotSupported is returned as error.
// If an overlay filesystem is not supported over an 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
	}

	// require kernel 4.0.0 to ensure multiple lower dirs are supported
	v, err := kernel.GetKernelVersion()
	if err != nil {
		return nil, err
	}
	if kernel.CompareKernelVersion(*v, kernel.VersionInfo{Kernel: 4, Major: 0, Minor: 0}) < 0 {
		if !opts.overrideKernelCheck {
			return nil, graphdriver.ErrNotSupported
		}
		logrus.Warn("Using pre-4.0.0 kernel for overlay2, mount failures may require kernel update")
	}

	fsMagic, err := graphdriver.GetFSMagic(home)
	if err != nil {
		return nil, err
	}
	if fsName, ok := graphdriver.FsNames[fsMagic]; ok {
		backingFs = fsName
	}

	// check if they are running over btrfs, aufs, zfs, overlay, or ecryptfs
	switch fsMagic {
	case graphdriver.FsMagicBtrfs, graphdriver.FsMagicAufs, graphdriver.FsMagicZfs, graphdriver.FsMagicOverlay, graphdriver.FsMagicEcryptfs:
		logrus.Errorf("'overlay2' is not supported over %s", backingFs)
		return nil, graphdriver.ErrIncompatibleFS
	}

	rootUID, rootGID, err := idtools.GetRootUIDGID(uidMaps, gidMaps)
	if err != nil {
		return nil, err
	}
	// Create the driver home dir
	if err := idtools.MkdirAllAs(path.Join(home, linkDir), 0700, rootUID, rootGID); err != nil && !os.IsExist(err) {
		return nil, err
	}

	if err := mount.MakePrivate(home); err != nil {
		return nil, err
	}

	supportsDType, err := fsutils.SupportsDType(home)
	if err != nil {
		return nil, err
	}
	if !supportsDType {
		// not a fatal error until v1.16 (#27443)
		logrus.Warn(overlayutils.ErrDTypeNotSupported("overlay2", backingFs))
	}

	d := &Driver{
		home:          home,
		uidMaps:       uidMaps,
		gidMaps:       gidMaps,
		ctr:           graphdriver.NewRefCounter(graphdriver.NewFsChecker(graphdriver.FsMagicOverlay)),
		supportsDType: supportsDType,
	}

	d.naiveDiff = graphdriver.NewNaiveDiffDriver(d, uidMaps, gidMaps)

	if backingFs == "xfs" {
		// Try to enable project quota support over xfs.
		if d.quotaCtl, err = quota.NewControl(home); err == nil {
			projectQuotaSupported = true
		}
	}

	logrus.Debugf("backingFs=%s,  projectQuotaSupported=%v", backingFs, projectQuotaSupported)

	return d, nil
}