external tail_n : t -> int -> string -> string array = "ocaml_guestfs_tail_n"
external df : t -> string = "ocaml_guestfs_df"
external df_h : t -> string = "ocaml_guestfs_df_h"
external tail_n : t -> int -> string -> string array = "ocaml_guestfs_tail_n"
external df : t -> string = "ocaml_guestfs_df"
external df_h : t -> string = "ocaml_guestfs_df_h"