From a547b3b04b7f16f225d248549a4cc16a91498254 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sat, 29 Nov 2025 23:08:03 -0500
Subject: [PATCH] Enable content-addressed derivations.

ref: https://www.tweag.io/blog/2020-09-10-nix-cas/
---
 nix/configuration/configuration.nix           | 33 ++++++++++---------
 .../roles/distributed_build/default.nix       |  3 +-
 2 files changed, 20 insertions(+), 16 deletions(-)

diff --git a/nix/configuration/configuration.nix b/nix/configuration/configuration.nix
index d1375bd..5815429 100644
--- a/nix/configuration/configuration.nix
+++ b/nix/configuration/configuration.nix
@@ -102,6 +102,9 @@
     nix.settings.experimental-features = [
       "nix-command"
       "flakes"
+      "ca-derivations"
+      # "blake3-hashes"
+      # "git-hashing"
     ];
     nix.settings.trusted-users = [ "@wheel" ];
 
@@ -162,22 +165,22 @@
         );
       in
       [
-        (final: prev: {
-          imagemagick = prev.imagemagick.overrideAttrs (old: rec {
-            # 7.1.2-6 seems to no longer exist, so use 7.1.2-7
-            version = "7.1.2-7";
+        # (final: prev: {
+        #   imagemagick = prev.imagemagick.overrideAttrs (old: rec {
+        #     # 7.1.2-6 seems to no longer exist, so use 7.1.2-7
+        #     version = "7.1.2-7";
 
-            src = final.fetchFromGitHub {
-              owner = "ImageMagick";
-              repo = "ImageMagick";
-              tag = version;
-              hash = "sha256-9ARCYftoXiilpJoj+Y+aLCEqLmhHFYSrHfgA5DQHbGo=";
-            };
-          });
-        })
-        (final: prev: {
-          grub2 = (final.callPackage ./package/grub { });
-        })
+        #     src = final.fetchFromGitHub {
+        #       owner = "ImageMagick";
+        #       repo = "ImageMagick";
+        #       tag = version;
+        #       hash = "sha256-9ARCYftoXiilpJoj+Y+aLCEqLmhHFYSrHfgA5DQHbGo=";
+        #     };
+        #   });
+        # })
+        # (final: prev: {
+        #   grub2 = (final.callPackage ./package/grub { });
+        # })
       ];
 
     # This option defines the first version of NixOS you have installed on this particular machine,
diff --git a/nix/configuration/roles/distributed_build/default.nix b/nix/configuration/roles/distributed_build/default.nix
index dc2d680..012d413 100644
--- a/nix/configuration/roles/distributed_build/default.nix
+++ b/nix/configuration/roles/distributed_build/default.nix
@@ -58,7 +58,8 @@ in
       {
         nix.distributedBuilds = true;
 
-        nix.settings.substituters = lib.mkForce [ "ssh://hydra" ];
+        # https://nix.dev/manual/nix/2.32/store/types/ssh-store.html
+        nix.settings.substituters = lib.mkForce [ "ssh://hydra?compress=true&log-fd=2&max-connections=4" ];
         nix.settings.substitute = lib.mkForce true;
         nix.settings.post-build-hook = pkgs.writeShellScript "post-build-hook" ''
           set -euo pipefail