external umount_all : t -> unit = "ocaml_guestfs_umount_all"
external lvm_remove_all : t -> unit = "ocaml_guestfs_lvm_remove_all"
external file : t -> string -> string = "ocaml_guestfs_file"
+external command : t -> string array -> string = "ocaml_guestfs_command"
+external command_lines : t -> string array -> string array = "ocaml_guestfs_command_lines"