diff --git a/bin/builder_db.ml b/bin/builder_db.ml
index 5630dc5..0232d6c 100644
--- a/bin/builder_db.ml
+++ b/bin/builder_db.ml
@@ -4,10 +4,10 @@ let ( let+ ) x f = Result.map f x
 let or_die exit_code = function
   | Ok r -> r
   | Error (`Msg msg) ->
-    Format.eprintf "Error: %s" msg;
+    Format.eprintf "Error: %s\n" msg;
     exit exit_code
   | Error (#Caqti_error.t as e) ->
-    Format.eprintf "Database error: %a" Caqti_error.pp e;
+    Format.eprintf "Database error: %a\n" Caqti_error.pp e;
     exit exit_code
 
 let foreign_keys =
@@ -320,22 +320,35 @@ let help man_format cmds = function
     then `Help (man_format, Some cmd)
     else `Error (true, "Unknown command: " ^ cmd)
 
+let uname =
+  let cmd = Bos.Cmd.(v "uname" % "-s") in
+  lazy (match Bos.OS.Cmd.(run_out cmd |> out_string |> success) with
+      | Ok s when s = "FreeBSD" -> `FreeBSD
+      | Ok s when s = "Linux" -> `Linux
+      | Ok s -> invalid_arg (Printf.sprintf "OS %s not supported\n" s)
+      | Error (`Msg m) -> invalid_arg m)
+
+let default_datadir =
+  match Lazy.force uname with
+  | `FreeBSD -> "/var/db/builder-web"
+  | `Linux -> "/var/lib/builder-web"
+
 let dbpath =
   let doc = "sqlite3 database path" in
   Cmdliner.Arg.(value &
-                opt non_dir_file "/var/db/builder-web/builder.sqlite3" &
+                opt non_dir_file (default_datadir ^ "/builder.sqlite3") &
                 info ~doc ["dbpath"])
 
 let dbpath_new =
   let doc = "sqlite3 database path" in
   Cmdliner.Arg.(value &
-                opt string "/var/db/builder-web/builder.sqlite3" &
+                opt string (default_datadir ^ "/builder.sqlite3") &
                 info ~doc ["dbpath"])
 
 let datadir =
   let doc = "data directory" in
   Cmdliner.Arg.(value &
-                opt dir "/var/db/builder-web/" &
+                opt dir default_datadir &
                 info ~doc ["datadir"])
 
 let jobname =
diff --git a/bin/builder_web_app.ml b/bin/builder_web_app.ml
index 0c5cd0a..37829bc 100644
--- a/bin/builder_web_app.ml
+++ b/bin/builder_web_app.ml
@@ -120,9 +120,22 @@ let ip_port : (Ipaddr.V4.t * int) Arg.converter =
   in
   parse, fun ppf (ip, port) -> Format.fprintf ppf "%a:%d" Ipaddr.V4.pp ip port
 
+let uname =
+  let cmd = Bos.Cmd.(v "uname" % "-s") in
+  lazy (match Bos.OS.Cmd.(run_out cmd |> out_string |> success) with
+      | Ok s when s = "FreeBSD" -> `FreeBSD
+      | Ok s when s = "Linux" -> `Linux
+      | Ok s -> invalid_arg (Printf.sprintf "OS %s not supported" s)
+      | Error (`Msg m) -> invalid_arg m)
+
+let default_datadir =
+  match Lazy.force uname with
+  | `FreeBSD -> "/var/db/builder-web"
+  | `Linux -> "/var/lib/builder-web"
+
 let datadir =
   let doc = "data directory" in
-  Arg.(value & opt dir "/var/db/builder-web/" & info [ "d"; "datadir" ] ~doc)
+  Arg.(value & opt dir default_datadir & info [ "d"; "datadir" ] ~doc)
 
 let port =
   let doc = "port" in
diff --git a/bin/migrations/builder_migrations.ml b/bin/migrations/builder_migrations.ml
index ea8d001..ab83d49 100644
--- a/bin/migrations/builder_migrations.ml
+++ b/bin/migrations/builder_migrations.ml
@@ -24,7 +24,7 @@ let pp_error ppf = function
 let or_die exit_code = function
   | Ok r -> r
   | Error e ->
-    Format.eprintf "Database error: %a" pp_error e;
+    Format.eprintf "Database error: %a\n" pp_error e;
     exit exit_code
 
 let do_database_action action () datadir =
@@ -59,10 +59,23 @@ let help man_format migrations = function
     then `Help (man_format, Some migration)
     else `Error (true, "Unknown migration: " ^ migration)
 
+let uname =
+  let cmd = Bos.Cmd.(v "uname" % "-s") in
+  lazy (match Bos.OS.Cmd.(run_out cmd |> out_string |> success) with
+      | Ok s when s = "FreeBSD" -> `FreeBSD
+      | Ok s when s = "Linux" -> `Linux
+      | Ok s -> invalid_arg (Printf.sprintf "OS %s not supported" s)
+      | Error (`Msg m) -> invalid_arg m)
+
+let default_datadir =
+  match Lazy.force uname with
+  | `FreeBSD -> "/var/db/builder-web"
+  | `Linux -> "/var/lib/builder-web"
+
 let datadir =
   let doc = "data directory containing builder.sqlite3 and data files" in
   Cmdliner.Arg.(value &
-                opt dir "/var/db/builder-web/" &
+                opt dir default_datadir &
                 info ~doc ["datadir"])
 
 let setup_log =
diff --git a/bin/migrations/m20210308.ml b/bin/migrations/m20210308.ml
index 0a02b0c..faac6f5 100644
--- a/bin/migrations/m20210308.ml
+++ b/bin/migrations/m20210308.ml
@@ -10,13 +10,13 @@ let broken_builds =
           WHERE a.build = b.id and a.filepath = b.main_binary) = 0
     |}
 
-let fixup _datadir (module Db : Caqti_blocking.CONNECTION) =
+let fixup datadir (module Db : Caqti_blocking.CONNECTION) =
   let open Grej.Infix in
   Grej.check_version ~user_version:3L (module Db) >>= fun () ->
   Db.rev_collect_list broken_builds () >>= fun broken_builds ->
   Grej.list_iter_result
     (fun ((build, uuid, job_name) : [`build] Rep.id * Uuidm.t * string) ->
-       Format.printf "Removing job %a.\nPlease clean up data files in /var/db/builder-web/%s/%a\n"
-         Uuidm.pp uuid job_name Uuidm.pp uuid;
+       Format.printf "Removing job %a.\nPlease clean up data files in %a/%s/%a\n"
+         Uuidm.pp uuid Fpath.pp datadir job_name Uuidm.pp uuid;
        Db.exec Builder_db.Build.remove build)
     broken_builds