diff --git a/.ocamlformat b/.ocamlformat
index e80baea..187e7df 100644
--- a/.ocamlformat
+++ b/.ocamlformat
@@ -1 +1 @@
-version=0.27.0
+version=0.29.0
diff --git a/bin/dune b/bin/dune
new file mode 100644
index 0000000..46e05a5
--- /dev/null
+++ b/bin/dune
@@ -0,0 +1,8 @@
+(executable
+ (name main)
+ (public_name opentrace)
+ (preprocess
+  (pps ppx_blob))
+ (preprocessor_deps
+  (file ../lib/opentrace.bpf.o))
+ (libraries eio_posix opentrace))
diff --git a/opentrace.ml b/bin/main.ml
similarity index 98%
rename from opentrace.ml
rename to bin/main.ml
index 97966e7..e56df73 100644
--- a/opentrace.ml
+++ b/bin/main.ml
@@ -1,10 +1,11 @@
+open Opentrace
 open Libbpf
 open Libbpf_maps
 
 type format = Csv | Json
 
 let obj_path = "opentrace.bpf.o"
-let obj_file = [%blob "opentrace.bpf.o"]
+let obj_file = [%blob "../lib/opentrace.bpf.o"]
 
 let program_names =
   [
@@ -209,8 +210,10 @@ let exec format output user poll (prog, args) open_flags_filter cgroups =
       Condition.wait start_process mutex;
       Eio.Switch.run @@ fun sw ->
       with_cgroup cgroups @@ fun group ->
-      let process = Spawn.make_process group (Some uid) in
-      let p = Eio.Process.spawn process ~sw (prog :: args) in
+      let process = Spawn.make_process group in
+      let p =
+        Eio_unix.Process.spawn_unix ~uid ~fds:[] process ~sw (prog :: args)
+      in
       Atomic.set pid (Some (Eio.Process.pid p));
       let stat =
         Option.map
diff --git a/dune-project b/dune-project
index 04ac888..cd97086 100644
--- a/dune-project
+++ b/dune-project
@@ -11,7 +11,7 @@
   (description "")
   (depends
     (ocaml (>= 5.2.0))
-    eio_main
+    (eio_posix (>= 1.4)) 
     menhir
     cmdliner
     ppx_blob
diff --git a/dune b/lib/dune
similarity index 94%
rename from dune
rename to lib/dune
index 366b044..0cacaa8 100644
--- a/dune
+++ b/lib/dune
@@ -3,10 +3,9 @@
 
 (ocamllex lexer)
 
-(executable
+(library
  (name opentrace)
  (public_name opentrace)
- (modules opentrace config parser filter lexer spawn)
  (foreign_stubs
   (language c)
   (flags :standard -D_LARGEFILE64_SOURCE)
diff --git a/filter.ml b/lib/filter.ml
similarity index 100%
rename from filter.ml
rename to lib/filter.ml
diff --git a/include/discover.ml b/lib/include/discover.ml
similarity index 100%
rename from include/discover.ml
rename to lib/include/discover.ml
diff --git a/include/dune b/lib/include/dune
similarity index 100%
rename from include/dune
rename to lib/include/dune
diff --git a/lexer.mll b/lib/lexer.mll
similarity index 100%
rename from lexer.mll
rename to lib/lexer.mll
diff --git a/opentrace.bpf.c b/lib/opentrace.bpf.c
similarity index 100%
rename from opentrace.bpf.c
rename to lib/opentrace.bpf.c
diff --git a/opentrace_stubs.c b/lib/opentrace_stubs.c
similarity index 51%
rename from opentrace_stubs.c
rename to lib/opentrace_stubs.c
index c63499f..f4b4871 100644
--- a/opentrace_stubs.c
+++ b/lib/opentrace_stubs.c
@@ -12,39 +12,18 @@
 
 #include "include/fork_action.h"
 
-static void action_setuid(int errors, value v_config) {
-  #ifdef _WIN32
-  eio_unix_fork_error(errors, "action_setuid", "Unsupported operation on windows");
-  #else
-  value v_uid = Field(v_config, 1);
-  int r;
-  r = setuid(Int_val(v_uid));
-  if (r != 0) {
-    eio_unix_fork_error(errors, "setuid", strerror(errno));
-    _exit(1);
-  }
-  #endif
-}
-
-CAMLprim value eio_unix_fork_setuid(value v_unit) {
-  return Val_fork_fn(action_setuid);
-}
-
 static void action_setcgroup(int errors, value v_config) {
   value v_path = Field(v_config, 1);
 
-  int r;
   pid_t pid = getpid();
   FILE *f = fopen(String_val(v_path), "w");
   if (f == NULL) {
-	  eio_unix_fork_error(errors, "cgroup", strerror(errno));
-	  _exit(1);
+	  eio_unix_fork_error(errors, "cgroup", errno);
   }
 
   if (fprintf(f, "%d\n", pid) < 0) {
 	fclose(f);
-	eio_unix_fork_error(errors, "cgroup", strerror(errno));
-	_exit(1);
+	eio_unix_fork_error(errors, "cgroup", errno);
   }
 
   fclose(f);
diff --git a/parser.mly b/lib/parser.mly
similarity index 100%
rename from parser.mly
rename to lib/parser.mly
diff --git a/spawn.ml b/lib/spawn.ml
similarity index 65%
rename from spawn.ml
rename to lib/spawn.ml
index 878de81..a84d920 100644
--- a/spawn.ml
+++ b/lib/spawn.ml
@@ -31,15 +31,6 @@ let process =
 module T = struct
   type t = unit
 
-  external action_setuid : unit -> Eio_unix.Private.Fork_action.fork_fn
-    = "eio_unix_fork_setuid"
-
-  let action_setuid = action_setuid ()
-
-  let setuid (uid : int) =
-    Eio_unix.Private.Fork_action.
-      { run = (fun k -> k (Obj.repr (action_setuid, uid))) }
-
   external action_setcgroup : unit -> Eio_unix.Private.Fork_action.fork_fn
     = "eio_unix_fork_setcgroup"
 
@@ -49,13 +40,40 @@ module T = struct
     Eio_unix.Private.Fork_action.
       { run = (fun k -> k (Obj.repr (action_setcgroup, group))) }
 
-  let spawn_unix () ~group ~uid ~sw ?cwd ~env ~fds ~executable args =
+  let spawn_unix () ~group ~sw ?cwd ?pgid ?uid ?gid ?login_tty ~env ~fds
+      ~executable args =
+    let login_tty_action, fds =
+      match login_tty with
+      | None -> ([], fds)
+      | Some tty ->
+          let fds =
+            [ (0, tty, `Blocking); (1, tty, `Blocking); (2, tty, `Blocking) ]
+            @ fds
+          in
+          ([ Eio_unix.Private.Fork_action.login_tty tty ], fds)
+    in
+    let actions =
+      Low_level.Process.Fork_action.(
+        login_tty_action
+        @ [
+            Eio_unix.Private.Fork_action.inherit_fds fds;
+            execve executable ~argv:(Array.of_list args) ~env;
+          ])
+    in
+    let actions =
+      match pgid with
+      | None -> actions
+      | Some pgid -> Eio_unix.Private.Fork_action.setpgid pgid :: actions
+    in
     let actions =
-      Low_level.Process.Fork_action.
-        [ inherit_fds fds; execve executable ~argv:(Array.of_list args) ~env ]
+      match uid with
+      | None -> actions
+      | Some uid -> Eio_unix.Private.Fork_action.setuid uid :: actions
     in
     let actions =
-      match uid with None -> actions | Some uid -> setuid uid :: actions
+      match gid with
+      | None -> actions
+      | Some gid -> Eio_unix.Private.Fork_action.setgid gid :: actions
     in
     let actions =
       match group with None -> actions | Some g -> setcgroup g :: actions
@@ -78,11 +96,11 @@ module T = struct
     process (Low_level.Process.spawn ~sw actions)
 end
 
-let make_process group uid =
+let make_process group =
   let module T = struct
     type t = unit
 
-    let spawn_unix = T.spawn_unix ~group ~uid
+    let spawn_unix = T.spawn_unix ~group
   end in
   let h = Eio_unix.Process.Pi.mgr_unix (module Eio_unix.Process.Make_mgr (T)) in
   Eio.Resource.T ((), h)
diff --git a/uring.h b/lib/uring.h
similarity index 100%
rename from uring.h
rename to lib/uring.h
diff --git a/opentrace.opam b/opentrace.opam
index 1c9470a..58b2582 100644
--- a/opentrace.opam
+++ b/opentrace.opam
@@ -5,8 +5,8 @@ description: ""
 depends: [
   "dune" {>= "3.14"}
   "ocaml" {>= "5.2.0"}
-  "eio_main"
-  "menhir"
+  "eio_posix" {>= "1.4"}
+  "menhir" {>= "20180523"}
   "cmdliner"
   "ppx_blob"
   "jsonm"