diff --git a/packages/extunix/extunix.0.3.1/opam b/packages/extunix/extunix.0.3.1/opam
new file mode 100644
index 00000000000..fc8f62d1705
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+++ b/packages/extunix/extunix.0.3.1/opam
@@ -0,0 +1,69 @@
+# This file is generated by dune, edit dune-project instead
+opam-version: "2.0"
+synopsis: "Collection of thin bindings to various low-level system API"
+description: """
+Motto: "Be to Unix, what extlib is to stdlib"
+
+* Implement thin C bindings that directly map to underlying system API.
+* Provide common consistent ocaml interface: naming convention, exceptions.
+* Simple to build - no extra dependencies.
+"""
+maintainer: ["ygrek@autistici.org"]
+authors: [
+  "Andre Nathan"
+  "Antonin Décimo"
+  "Dmitry Grebeniuk"
+  "François Bobot"
+  "Gerd Stolpmann"
+  "Goswin von Brederlow"
+  "Joshua Smith"
+  "Kaustuv Chaudhuri"
+  "Markus W. Weissmann"
+  "Mehdi Dogguy"
+  "Niki Yoshiuchi"
+  "Pierre Chambart"
+  "Roman Vorobets"
+  "Stéphane Glondu"
+  "Sylvain Le Gall"
+  "ygrek"
+  "Zhenya Lykhovyd"
+]
+license: "LGPL-2.1-only with OCaml-LGPL-linking-exception"
+tags: ["org:ygrek"]
+homepage: "https://ygrek.org/p/ocaml-extunix"
+doc: "https://ygrek.org/p/ocaml-extunix"
+bug-reports: "https://github.com/ygrek/extunix/issues"
+depends: [
+  "ocaml" {>= "4.06"}
+  "dune" {>= "2.2"}
+  "dune-configurator" {build}
+  "ppxlib" {>= "0.18"}
+  "ounit2" {with-test}
+  "base-bytes"
+  "base-bigarray"
+  "base-unix"
+]
+build: [
+  ["dune" "subst"] {dev}
+  [
+    "dune"
+    "build"
+    "-p"
+    name
+    "-j"
+    jobs
+    "@install"
+    "@runtest" {with-test}
+    "@doc" {with-doc}
+  ]
+]
+dev-repo: "git+https://github.com/ygrek/extunix.git"
+url {
+  src: "https://ygrek.org/p/release/ocaml-extunix/ocaml-extunix-0.3.1.tar.gz"
+  checksum: [
+    "md5=62f898ad617074dc2ed80ee48b8ffc0d"
+    "sha256=69a8a022eccc8a4ab2aa4df2f9f7075736b40293bbb69bb0a4bec03ad5bc46f5"
+    "sha512=9ff12902cef9847d3ed00e94fc75fb5a00369385163359b9ecf278c3f53bf322fddec830ae6d0785c5dd670c02c6b4ffdbae1c743f13d4c73186f674dc7e72e1"
+  ]
+  mirrors: "https://github.com/ygrek/extunix/releases/download/v0.3.1/ocaml-extunix-0.3.1.tar.gz"
+}