diff --git a/weed/mount/weedfs_dir_mkrm.go b/weed/mount/weedfs_dir_mkrm.go
index 63fe34f91..fb854b77e 100644
--- a/weed/mount/weedfs_dir_mkrm.go
+++ b/weed/mount/weedfs_dir_mkrm.go
@@ -13,6 +13,12 @@ import (
 	"time"
 )
 
+/** Create a directory
+ *
+ * Note that the mode argument may not have the type specification
+ * bits set, i.e. S_ISDIR(mode) can be false.  To obtain the
+ * correct directory type bits use  mode|S_IFDIR
+ * */
 func (wfs *WFS) Mkdir(cancel <-chan struct{}, in *fuse.MkdirIn, name string, out *fuse.EntryOut) (code fuse.Status) {
 
 	if s := checkName(name); s != fuse.OK {
@@ -73,6 +79,7 @@ func (wfs *WFS) Mkdir(cancel <-chan struct{}, in *fuse.MkdirIn, name string, out
 
 }
 
+/** Remove a directory */
 func (wfs *WFS) Rmdir(cancel <-chan struct{}, header *fuse.InHeader, name string) (code fuse.Status) {
 
 	if name == "." {
diff --git a/weed/mount/weedfs_dir_read.go b/weed/mount/weedfs_dir_read.go
index 96fd36ffe..3a187aa1c 100644
--- a/weed/mount/weedfs_dir_read.go
+++ b/weed/mount/weedfs_dir_read.go
@@ -13,18 +13,56 @@ import (
 
 // Directory handling
 
+/** Open directory
+ *
+ * Unless the 'default_permissions' mount option is given,
+ * this method should check if opendir is permitted for this
+ * directory. Optionally opendir may also return an arbitrary
+ * filehandle in the fuse_file_info structure, which will be
+ * passed to readdir, releasedir and fsyncdir.
+ */
 func (wfs *WFS) OpenDir(cancel <-chan struct{}, input *fuse.OpenIn, out *fuse.OpenOut) (code fuse.Status) {
 	if !wfs.inodeToPath.HasInode(input.NodeId) {
 		return fuse.ENOENT
 	}
 	return fuse.OK
 }
+
+/** Release directory
+ *
+ * If the directory has been removed after the call to opendir, the
+ * path parameter will be NULL.
+ */
 func (wfs *WFS) ReleaseDir(input *fuse.ReleaseIn) {
 }
+
+/** Synchronize directory contents
+ *
+ * If the directory has been removed after the call to opendir, the
+ * path parameter will be NULL.
+ *
+ * If the datasync parameter is non-zero, then only the user data
+ * should be flushed, not the meta data
+ */
 func (wfs *WFS) FsyncDir(cancel <-chan struct{}, input *fuse.FsyncIn) (code fuse.Status) {
 	return fuse.OK
 }
 
+/** Read directory
+ *
+ * The filesystem may choose between two modes of operation:
+ *
+ * 1) The readdir implementation ignores the offset parameter, and
+ * passes zero to the filler function's offset.  The filler
+ * function will not return '1' (unless an error happens), so the
+ * whole directory is read in a single readdir operation.
+ *
+ * 2) The readdir implementation keeps track of the offsets of the
+ * directory entries.  It uses the offset parameter and always
+ * passes non-zero offset to the filler function.  When the buffer
+ * is full (or an error happens) the filler function will return
+ * '1'.
+ */
 func (wfs *WFS) ReadDir(cancel <-chan struct{}, input *fuse.ReadIn, out *fuse.DirEntryList) (code fuse.Status) {
 	return wfs.doReadDirectory(input, out, false)
 }
diff --git a/weed/mount/weedfs_file_mkrm.go b/weed/mount/weedfs_file_mkrm.go
index b5ade894e..82da45179 100644
--- a/weed/mount/weedfs_file_mkrm.go
+++ b/weed/mount/weedfs_file_mkrm.go
@@ -10,6 +10,26 @@ import (
 	"time"
 )
 
+/**
+ * Create and open a file
+ *
+ * If the file does not exist, first create it with the specified
+ * mode, and then open it.
+ *
+ * If this method is not implemented or under Linux kernel
+ * versions earlier than 2.6.15, the mknod() and open() methods
+ * will be called instead.
+ */
+func (wfs *WFS) Create(cancel <-chan struct{}, in *fuse.CreateIn, name string, out *fuse.CreateOut) (code fuse.Status) {
+	return fuse.ENOSYS
+}
+
+/** Create a file node
+ *
+ * This is called for creation of all non-directory, non-symlink
+ * nodes.  If the filesystem defines a create() method, then for
+ * regular files that will be called instead.
+ */
 func (wfs *WFS) Mknod(cancel <-chan struct{}, in *fuse.MknodIn, name string, out *fuse.EntryOut) (code fuse.Status) {
 
 	if s := checkName(name); s != fuse.OK {
@@ -73,6 +93,7 @@ func (wfs *WFS) Mknod(cancel <-chan struct{}, in *fuse.MknodIn, name string, out
 
 }
 
+/** Remove a file */
 func (wfs *WFS) Unlink(cancel <-chan struct{}, header *fuse.InHeader, name string) (code fuse.Status) {
 
 	dirFullPath := wfs.inodeToPath.GetPath(header.NodeId)
diff --git a/weed/mount/weedfs_symlink.go b/weed/mount/weedfs_symlink.go
index 3c36717d1..2c66db7f4 100644
--- a/weed/mount/weedfs_symlink.go
+++ b/weed/mount/weedfs_symlink.go
@@ -11,6 +11,7 @@ import (
 	"time"
 )
 
+/** Create a symbolic link */
 func (wfs *WFS) Symlink(cancel <-chan struct{}, header *fuse.InHeader, target string, name string, out *fuse.EntryOut) (code fuse.Status) {
 
 	if s := checkName(name); s != fuse.OK {
diff --git a/weed/mount/weedfs_unsupported.go b/weed/mount/weedfs_unsupported.go
new file mode 100644
index 000000000..218486d5c
--- /dev/null
+++ b/weed/mount/weedfs_unsupported.go
@@ -0,0 +1,65 @@
+package mount
+
+import "github.com/hanwen/go-fuse/fuse"
+
+// https://github.com/libfuse/libfuse/blob/48ae2e72b39b6a31cb2194f6f11786b7ca06aac6/include/fuse.h#L778
+
+/**
+ * Copy a range of data from one file to anotherNiels de Vos, 4 years ago: • libfuse: add copy_file_range() support
+ *
+ * Performs an optimized copy between two file descriptors without the
+ * additional cost of transferring data through the FUSE kernel module
+ * to user space (glibc) and then back into the FUSE filesystem again.
+ *
+ * In case this method is not implemented, applications are expected to
+ * fall back to a regular file copy.   (Some glibc versions did this
+ * emulation automatically, but the emulation has been removed from all
+ * glibc release branches.)
+ */
+func (wfs *WFS) CopyFileRange(cancel <-chan struct{}, in *fuse.CopyFileRangeIn) (written uint32, code fuse.Status) {
+	return 0, fuse.ENOSYS
+}
+
+/**
+ * Allocates space for an open file
+ *
+ * This function ensures that required space is allocated for specified
+ * file.  If this function returns success then any subsequent write
+ * request to specified range is guaranteed not to fail because of lack
+ * of space on the file system media.
+ */
+func (wfs *WFS) Fallocate(cancel <-chan struct{}, in *fuse.FallocateIn) (code fuse.Status) {
+	return fuse.ENOSYS
+}
+
+/**
+ * Find next data or hole after the specified offset
+ */
+func (wfs *WFS) Lseek(cancel <-chan struct{}, in *fuse.LseekIn, out *fuse.LseekOut) fuse.Status {
+	return fuse.ENOSYS
+}
+
+func (wfs *WFS) GetLk(cancel <-chan struct{}, in *fuse.LkIn, out *fuse.LkOut) (code fuse.Status) {
+	return fuse.ENOSYS
+}
+
+func (wfs *WFS) SetLk(cancel <-chan struct{}, in *fuse.LkIn) (code fuse.Status) {
+	return fuse.ENOSYS
+}
+
+func (wfs *WFS) SetLkw(cancel <-chan struct{}, in *fuse.LkIn) (code fuse.Status) {
+	return fuse.ENOSYS
+}
+
+/**
+ * Check file access permissions
+ *
+ * This will be called for the access() system call.  If the
+ * 'default_permissions' mount option is given, this method is not
+ * called.
+ *
+ * This method is not called under Linux kernel versions 2.4.x
+ */
+func (wfs *WFS) Access(cancel <-chan struct{}, input *fuse.AccessIn) (code fuse.Status) {
+	return fuse.ENOSYS
+}