From 77b41a90e242e4a3bb12ba357067c4b0221bc732 Mon Sep 17 00:00:00 2001
From: Rodrigo Arias Mallo <rodrigo.arias@bsc.es>
Date: Mon, 18 Sep 2023 18:06:51 +0200
Subject: [PATCH] Patch nix instead of using an override unit

---
 m/module/shared-nix-store.nix | 14 +++++++++++---
 pkgs/nix-socket.patch         | 11 +++++++++++
 pkgs/overlay.nix              |  4 ++++
 3 files changed, 26 insertions(+), 3 deletions(-)
 create mode 100644 pkgs/nix-socket.patch

diff --git a/m/module/shared-nix-store.nix b/m/module/shared-nix-store.nix
index af9c147..72eab92 100644
--- a/m/module/shared-nix-store.nix
+++ b/m/module/shared-nix-store.nix
@@ -11,9 +11,17 @@
   # One solution is to make the nix-daemon.socket depend only on the socket
   # patch (which is already covered by ConditionPathIsReadWrite =
   # /nix/var/nix/daemon-socket), instead on the /nix/store.
-  systemd.sockets.nix-daemon.unitConfig = {
-    RequiresMountsFor = "/nix/var/nix/daemon-socket";
-  };
+  #
+  # Using systemd.sockets.nix-daemon.unitConfig.RequiresMountsFor =
+  # "/nix/var/nix/daemon-socket" doesn't work, as the the mount options get
+  # added by systemd when the override config is merged with the one that Nix
+  # provides:
+  #
+  # owl2% sudo systemctl show nix-daemon.socket | grep RequiresMountsFor
+  # RequiresMountsFor=/nix/store /nix/var/nix/daemon-socket/socket /nix/var/nix/daemon-socket
+  # 
+  # To fix this, the Nix package is patched to only depend on /nix/var instead.
+  # See ../../pkgs/overlay.nix for details.
 
   # Mount the hut nix store via NFS in read-only mode.
   fileSystems."/mnt/hut-nix-store" = {
diff --git a/pkgs/nix-socket.patch b/pkgs/nix-socket.patch
new file mode 100644
index 0000000..44a66f9
--- /dev/null
+++ b/pkgs/nix-socket.patch
@@ -0,0 +1,11 @@
+--- a/misc/systemd/nix-daemon.socket.in	1970-01-01 01:00:01.000000000 +0100
++++ b/misc/systemd/nix-daemon.socket.in	2023-09-18 17:53:32.351760208 +0200
+@@ -1,7 +1,7 @@
+ [Unit]
+ Description=Nix Daemon Socket
+ Before=multi-user.target
+-RequiresMountsFor=@storedir@
++RequiresMountsFor=@localstatedir@
+ ConditionPathIsReadWrite=@localstatedir@/nix/daemon-socket
+ 
+ [Socket]
diff --git a/pkgs/overlay.nix b/pkgs/overlay.nix
index 03208c5..f731209 100644
--- a/pkgs/overlay.nix
+++ b/pkgs/overlay.nix
@@ -32,4 +32,8 @@ final: prev:
     lua = prev.lua5_4;
     fmt = prev.fmt_8;
   }) ceph ceph-client;
+
+  nix = prev.nix.overrideAttrs (old: {
+    patches = old.patches ++ [ ./nix-socket.patch ];
+  });
 }