diff --git a/docs/content/local.md b/docs/content/local.md
index 28f8a0715..3858e62fe 100644
--- a/docs/content/local.md
+++ b/docs/content/local.md
@@ -74,3 +74,48 @@ And use rclone like this:
 This will use UNC paths on `c:\src` but not on `z:\dst`.
 Of course this will cause problems if the absolute path length of a
 file exceeds 258 characters on z, so only use this option if you have to.
+
+### Specific options ###
+
+Here are the command line options specific to local storage
+
+#### --one-file-system, -x ####
+
+This tells rclone to stay in the filesystem specified by the root and
+not to recurse into different file systems.
+
+For example if you have a directory heirachy like this
+
+```
+root
+├── disk1     - disk1 mounted on the root
+│   └── file3 - stored on disk1
+├── disk2     - disk2 mounted on the root
+│   └── file4 - stored on disk12
+├── file1     - stored on the root disk
+└── file2     - stored on the root disk
+```
+
+Using `rclone --one-file-system copy root remote:` will only copy `file1` and `file2`.  Eg
+
+```
+$ rclone -q --one-file-system ls root
+        0 file1
+        0 file2
+```
+
+```
+$ rclone -q ls root
+        0 disk1/file3
+        0 disk2/file4
+        0 file1
+        0 file2
+```
+
+**NB** Rclone (like most unix tools such as `du`, `rsync` and `tar`)
+treats a bind mount to the same device as being on the same
+filesystem.
+
+**NB** This flag is only available on Unix based systems.  On systems
+where it isn't supported (eg Windows) it will not appear as an valid
+flag.
diff --git a/local/local.go b/local/local.go
index c0ca3f56a..1974f1044 100644
--- a/local/local.go
+++ b/local/local.go
@@ -12,7 +12,6 @@ import (
 	"runtime"
 	"strings"
 	"sync"
-	"syscall"
 	"time"
 	"unicode/utf8"
 
@@ -20,10 +19,10 @@ import (
 
 	"github.com/ncw/rclone/fs"
 	"github.com/pkg/errors"
-	"github.com/spf13/pflag"
 )
 
-var oneFileSystem = pflag.BoolP("one-file-system", "x", false, "Don't cross filesystem boundaries.")
+// Constants
+const devUnset = 0xdeadbeefcafebabe // a device id meaning it is unset
 
 // Register with Fs
 func init() {
@@ -48,6 +47,7 @@ func init() {
 type Fs struct {
 	name        string              // the name of the remote
 	root        string              // The root directory (OS path)
+	dev         uint64              // device number of root node
 	precisionOk sync.Once           // Whether we need to read the precision
 	precision   time.Duration       // precision of local filesystem
 	wmu         sync.Mutex          // used for locking access to 'warned'.
@@ -75,11 +75,15 @@ func NewFs(name, root string) (fs.Fs, error) {
 		name:   name,
 		warned: make(map[string]struct{}),
 		nounc:  nounc == "true",
+		dev:    devUnset,
 	}
 	f.root = f.cleanPath(root)
 
 	// Check to see if this points to a file
 	fi, err := os.Lstat(f.root)
+	if err == nil {
+		f.dev = readDevice(fi)
+	}
 	if err == nil && fi.Mode().IsRegular() {
 		// It is a file, so use the parent as the root
 		f.root, _ = getDirFile(f.root)
@@ -156,14 +160,6 @@ func (f *Fs) list(out fs.ListOpts, remote string, dirpath string, level int) (su
 		return nil
 	}
 
-	// Obtain dirpath's device
-	fdFi, err := os.Stat(dirpath)
-	if err != nil {
-		out.SetError(errors.Wrapf(err, "failed to stat directory %q", dirpath))
-		return nil
-	}
-	fdDev := fdFi.Sys().(*syscall.Stat_t).Dev
-
 	defer func() {
 		err := fd.Close()
 		if err != nil {
@@ -199,7 +195,7 @@ func (f *Fs) list(out fs.ListOpts, remote string, dirpath string, level int) (su
 					if out.AddDir(dir) {
 						return nil
 					}
-					if level > 0 && !(*oneFileSystem && !((fi.Sys().(*syscall.Stat_t)).Dev == fdDev)) {
+					if level > 0 && f.dev == readDevice(fi) {
 						subdirs = append(subdirs, listArgs{remote: newRemote, dirpath: newPath, level: level - 1})
 					}
 				}
@@ -302,7 +298,16 @@ func (f *Fs) Put(in io.Reader, src fs.ObjectInfo) (fs.Object, error) {
 // Mkdir creates the directory if it doesn't exist
 func (f *Fs) Mkdir() error {
 	// FIXME: https://github.com/syncthing/syncthing/blob/master/lib/osutil/mkdirall_windows.go
-	return os.MkdirAll(f.root, 0777)
+	err := os.MkdirAll(f.root, 0777)
+	if err != nil {
+		return err
+	}
+	fi, err := os.Lstat(f.root)
+	if err != nil {
+		return err
+	}
+	f.dev = readDevice(fi)
+	return nil
 }
 
 // Rmdir removes the directory
diff --git a/local/read_device_other.go b/local/read_device_other.go
new file mode 100644
index 000000000..1429c7ddc
--- /dev/null
+++ b/local/read_device_other.go
@@ -0,0 +1,13 @@
+// Device reading functions
+
+// +build !darwin,!dragonfly,!freebsd,!linux,!netbsd,!openbsd,!solaris
+
+package local
+
+import "os"
+
+// readDevice turns a valid os.FileInfo into a device number,
+// returning devUnset if it fails.
+func readDevice(fi os.FileInfo) uint64 {
+	return devUnset
+}
diff --git a/local/read_device_unix.go b/local/read_device_unix.go
new file mode 100644
index 000000000..472e72f8d
--- /dev/null
+++ b/local/read_device_unix.go
@@ -0,0 +1,31 @@
+// Device reading functions
+
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package local
+
+import (
+	"os"
+	"syscall"
+
+	"github.com/ncw/rclone/fs"
+	"github.com/spf13/pflag"
+)
+
+var (
+	oneFileSystem = pflag.BoolP("one-file-system", "x", false, "Don't cross filesystem boundaries.")
+)
+
+// readDevice turns a valid os.FileInfo into a device number,
+// returning devUnset if it fails.
+func readDevice(fi os.FileInfo) uint64 {
+	if !*oneFileSystem {
+		return devUnset
+	}
+	statT, ok := fi.Sys().(*syscall.Stat_t)
+	if !ok {
+		fs.Debug(fi.Name(), "Type assertion fi.Sys().(*syscall.Stat_t) failed from: %#v", fi.Sys())
+		return devUnset
+	}
+	return uint64(statT.Dev)
+}