Hi Rich, A compiling error occurs here, File "../ocaml/guestfs.ml", line 1, characters 0-1: Error: The implementation ../ocaml/guestfs.ml does not match the interface ../ocaml/guestfs.cmi: Values do not match: external mkfs_btrfs : t -> ?allocstart:int64 -> ?bytecount:int64 -> ?datatype:string -> ?leafsize:int -> ?label:string -> ?metadata:string -> ?nodesize:int -> ?sectorsize:int -> string array -> unit = "ocaml_guestfs_mkfs_btrfs_byte" "ocaml_guestfs_mkfs_btrfs" is not included in val mkfs_btrfs : t -> ?allocstart:int64 -> ?bytecount:int64 -> ?datatype:string -> ?leafsize:int -> ?label:string -> ?metadata:string -> ?nodesize:int -> ?sectorsize:int -> string -> unit make: *** [../ocaml/guestfs.cmx] Error 2 Thanks, Wanlong Gao