From 30679f9f4b4a0905885d59d9c012072b4d54b61c Mon Sep 17 00:00:00 2001
From: Jake Hillion <jake@hillion.co.uk>
Date: Sun, 2 Jun 2024 22:01:17 +0100
Subject: [PATCH] sodium: add cache directory on the sd card

---
 hosts/sodium.pop.ts.hillion.co.uk/default.nix | 19 ++++++++++++++++++-
 .../hardware-configuration.nix                |  7 +++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/hosts/sodium.pop.ts.hillion.co.uk/default.nix b/hosts/sodium.pop.ts.hillion.co.uk/default.nix
index 73386f7..9a2961e 100644
--- a/hosts/sodium.pop.ts.hillion.co.uk/default.nix
+++ b/hosts/sodium.pop.ts.hillion.co.uk/default.nix
@@ -1,4 +1,4 @@
-{ config, pkgs, lib, nixos-hardware, ... }:
+{ config, pkgs, nixpkgs-unstable, lib, nixos-hardware, ... }:
 
 {
   imports = [
@@ -23,6 +23,23 @@
 
     ## Impermanence
     custom.impermanence.enable = true;
+    boot.initrd.postDeviceCommands = lib.mkAfter ''
+      btrfs subvolume delete /cache/tmp
+      btrfs subvolume snapshot /cache/empty_snapshot /cache/tmp
+      chmod 0777 /cache/tmp
+      chmod +t /cache/tmp
+    '';
+
+    ### nix only supports build-dir from 2.22. bind mount /tmp to something persistent instead.
+    fileSystems."/tmp" = {
+      device = "/cache/tmp";
+      options = [ "bind" ];
+    };
+    # nix = {
+    #   settings = {
+    #     build-dir = "/cache/tmp/";
+    #   };
+    # };
 
     ## Custom Services
     custom.locations.autoServe = true;
diff --git a/hosts/sodium.pop.ts.hillion.co.uk/hardware-configuration.nix b/hosts/sodium.pop.ts.hillion.co.uk/hardware-configuration.nix
index 40b1764..925aafb 100644
--- a/hosts/sodium.pop.ts.hillion.co.uk/hardware-configuration.nix
+++ b/hosts/sodium.pop.ts.hillion.co.uk/hardware-configuration.nix
@@ -42,6 +42,13 @@
       options = [ "subvol=data" ];
     };
 
+  fileSystems."/cache" =
+    {
+      device = "/dev/disk/by-uuid/48ae82bd-4d7f-4be6-a9c9-4fcc29d4aac0";
+      fsType = "btrfs";
+      options = [ "subvol=cache" ];
+    };
+
   swapDevices = [ ];
 
   # Enables DHCP on each ethernet and wireless interface. In case of scripted networking