From e87f42e3a2d57fc18997983e3a04f972f83c5317 Mon Sep 17 00:00:00 2001
From: Alexander Sosedkin <monk@unboiled.info>
Date: Fri, 17 Dec 2021 01:28:46 +0100
Subject: [PATCH] modules/upgrade: fix missing /dev/shm on upgrade from <21.11

Fixes: #162
---
 modules/module-list.nix |  1 +
 modules/upgrade.nix     | 15 +++++++++++++++
 2 files changed, 16 insertions(+)
 create mode 100644 modules/upgrade.nix

diff --git a/modules/module-list.nix b/modules/module-list.nix
index bbd4269..511bcc3 100644
--- a/modules/module-list.nix
+++ b/modules/module-list.nix
@@ -17,6 +17,7 @@
   ./home-manager.nix
   ./nixpkgs/options.nix
   ./time.nix
+  ./upgrade.nix
   ./user.nix
   ./version.nix
   (pkgs.path + "/nixos/modules/misc/assertions.nix")
diff --git a/modules/upgrade.nix b/modules/upgrade.nix
new file mode 100644
index 0000000..1a5a4ce
--- /dev/null
+++ b/modules/upgrade.nix
@@ -0,0 +1,15 @@
+# Copyright (c) 2019-2021, see AUTHORS. Licensed under MIT License, see LICENSE.
+
+{ config, lib, ... }:
+
+{
+  config.build.activationAfter =
+    # TODO: remove when we stop supporting upgrades from <21.11
+    # Setups upgraded to 21.11 don't have the /dev/shm directory bootstrapped:
+    # https://github.com/t184256/nix-on-droid/issues/162
+    lib.mkIf (lib.versionOlder config.system.stateVersion "21.11") {
+      createDevShm = ''
+        mkdir -p ${config.build.installationDir}/dev/shm
+      '';
+    };
+}