diff --git a/bin/builder_db.ml b/bin/builder_db.ml
index bf3de3d..10b8e91 100644
--- a/bin/builder_db.ml
+++ b/bin/builder_db.ml
@@ -202,6 +202,43 @@ let verify_input_id () dbpath =
    in
    or_die 1 r
 
+let build_artifacts : (unit, (Fpath.t * Fpath.t * Cstruct.t * int64) * [`build] Builder_db.Rep.id, [ `One | `Zero | `Many ]) Caqti_request.t =
+  Caqti_request.collect
+    Caqti_type.unit
+    Caqti_type.(tup2 (tup4 Builder_db.Rep.fpath Builder_db.Rep.fpath Builder_db.Rep.cstruct int64) (Builder_db.Rep.id `build))
+    {| SELECT filepath, localpath, sha256, size, build FROM build_artifact |}
+
+let verify_data_dir () datadir =
+  let dbpath = datadir ^ "/builder.sqlite3" in
+  Logs.info (fun m -> m "connecting to %s" dbpath);
+  let r =
+    connect
+      (Uri.make ~scheme:"sqlite3" ~path:dbpath ~query:["create", ["false"]] ())
+    >>= fun (module Db : Caqti_blocking.CONNECTION)  ->
+    Db.collect_list build_artifacts () >>= fun build_artifacts ->
+    Logs.info (fun m -> m "total: %d artifacts" (List.length build_artifacts));
+    List.iteri (fun idx ((fpath, lpath, sha, size), _build_id) ->
+      if idx mod 100 = 0 then Logs.info (fun m -> m "%d" idx);
+      (match Fpath.segs lpath with
+       | _job :: _uuid :: output :: tl ->
+         if output = "output" && Fpath.equal (Fpath.v (String.concat "/" tl)) fpath then
+           ()
+         else
+           Logs.err (fun m -> m "lpath (%a) and fpath (%a) do not match" Fpath.pp lpath Fpath.pp lpath)
+       | _ -> Logs.err (fun m -> m "lpath is not of form <job>/<uuid>/<output>/<filename>: %a" Fpath.pp lpath));
+      let abs_path = Fpath.(v datadir // lpath) in
+      (match Bos.OS.File.read abs_path with
+       | Error (`Msg msg) -> Logs.err (fun m -> m "file %a not present: %s" Fpath.pp abs_path msg)
+       | Ok data ->
+           let s = Int64.of_int (String.length data) in
+           if s <> size then Logs.err (fun m -> m "File %a has different size (in DB %Lu on disk %Lu)" Fpath.pp abs_path size s);
+           let sh = Mirage_crypto.Hash.SHA256.digest (Cstruct.of_string data) in
+           if not (Cstruct.equal sha sh) then Logs.err (fun m -> m "File %a has different hash (in DB %a on disk %a" Fpath.pp abs_path Cstruct.hexdump_pp sha Cstruct.hexdump_pp sh))
+    ) build_artifacts;
+    Ok ()
+  in
+  or_die 1 r
+
 let help man_format cmds = function
   | None -> `Help (man_format, None)
   | Some cmd ->
@@ -331,6 +368,11 @@ let verify_input_id_cmd =
   (Cmdliner.Term.(pure verify_input_id $ setup_log $ dbpath),
    Cmdliner.Term.info ~doc "verify-input-id")
 
+let verify_data_dir_cmd =
+  let doc = "verify that the data directory is consistent with the build_artifact table" in
+  (Cmdliner.Term.(pure verify_data_dir $ setup_log $ datadir),
+   Cmdliner.Term.info ~doc "verify-data-dir")
+
 let help_cmd =
   let topic =
     let doc = "Command to get help on" in
@@ -352,5 +394,5 @@ let () =
     [help_cmd; migrate_cmd;
      user_add_cmd; user_update_cmd; user_remove_cmd; user_list_cmd; user_disable_cmd;
      access_add_cmd; access_remove_cmd; job_remove_cmd;
-     verify_input_id_cmd ]
+     verify_input_id_cmd; verify_data_dir_cmd ]
   |> Cmdliner.Term.exit