From f9451de1e7eec7a34e1b6968df76f365555ed598 Mon Sep 17 00:00:00 2001
From: dawn <dawn@tangled.org>
Date: Mon, 29 Jun 2026 12:32:28 +0000
Subject: [PATCH] nix/microvm: make sure tmp is diskbacked

Signed-off-by: dawn <dawn@tangled.org>
---
 nix/microvm/base.nix | 10 ++++++++++
 spindle/engines/microvm/test-spindle-microvm.sh | 8 +++++++-
 2 file(s) changed, 17 insertion(s)(+), 1 deletion(s)(-)

diff --git a/nix/microvm/base.nix b/nix/microvm/base.nix
--- a/nix/microvm/base.nix
+++ b/nix/microvm/base.nix
@@ -307,6 +307,13 @@
     options = ["bind"];
     depends = ["/persist"];
   };
+  # bind mount /tmp so our tmp is disk backed...
+  fileSystems."/tmp" = {
+    device = "/persist/tmp";
+    fsType = "none";
+    options = ["bind"];
+    depends = ["/persist"];
+  };
 
   # create bind sources before local-fs.target, which means we have to do this
   # at initrd time
@@ -322,6 +329,9 @@
     };
     "/sysroot/persist/var".d = {
       mode = "0755";
+    };
+    "/sysroot/persist/tmp".d = {
+      mode = "1777";
     };
   };
 }
diff --git a/spindle/engines/microvm/test-spindle-microvm.sh b/spindle/engines/microvm/test-spindle-microvm.sh
--- a/spindle/engines/microvm/test-spindle-microvm.sh
+++ b/spindle/engines/microvm/test-spindle-microvm.sh
@@ -500,10 +500,16 @@
         ;;
 esac
 
+if [ "$(stat -c %d /tmp)" = "$(stat -c %d /workspace)" ]; then
+    echo "tmp_on_persist=yes"
+else
+    echo "tmp_on_persist=no"
+fi
+
 /run/current-system/sw/bin/nix-store --realise "$store_path" >/dev/null
 ' bash "$test_store_path") || return 1
 
-    check_needles "$out" "^http_version=2(\\.0)?$" || return 1
+    check_needles "$out" "^http_version=2(\\.0)?$" "^tmp_on_persist=yes$" || return 1
     echo "success: store path realized from cache and cache proxy accepted cleartext HTTP/2"
 }
 

--
tangled.sh