Reset the partitions when initializing the disk

THIS DESTROYS DATA

mirage/partitions.ml

@@ -114,8 +114,6 @@ module Make(BLOCK : Mirage_block.S) = struct
         Lwt.return_error (`Msg "too small disk")
       else Lwt_result.return ()
     in
-    let gpt =
-      let partitions =
     (* Current implementation of [Gpt.Partition.make] only returns [Ok _] or
        raises [Invalid_argument _] :/ *)
     let attributes = 1L in
@@ -155,6 +153,8 @@ module Make(BLOCK : Mirage_block.S) = struct
         (Int64.pred git_dump.starting_lba)
       |> Result.get_ok
     in
+    let gpt =
+      let partitions =
         [ tar; git_dump; md5s; sha512s ]
       in
       Gpt.make ~sector_size ~disk_sectors:size_sectors partitions
@@ -167,6 +167,23 @@ module Make(BLOCK : Mirage_block.S) = struct
     Gpt.marshal_partition_table ~sector_size
       (Cstruct.shift buf (sector_size * Int64.to_int gpt.partition_entry_lba))
     gpt;
-    BLOCK.write block 0L [ buf ]
+    let write block sector_start buffers =
+      BLOCK.write block sector_start buffers
       |> Lwt_result.map_error (fun e -> `Block e)
+    in
+    let*? () =
+      write block 0L [ buf ]
+    in
+    (* Format the file systems by writing zeroes *)
+    let zeroes = Cstruct.create (max (2 * Tar.Header.length) sector_size) in
+    let*? () =
+      write block tar.starting_lba [ Cstruct.sub zeroes 0 (2 * Tar.Header.length) ]
+    in
+    let*? () =
+      write block git_dump.starting_lba [ Cstruct.sub zeroes 0 sector_size ]
+    in
+    let*? () =
+      write block md5s.starting_lba [ Cstruct.sub zeroes 0 sector_size ]
+    in
+    write block sha512s.starting_lba [ Cstruct.sub zeroes 0 sector_size ]
 end