From 5291925fd2486175e781669412fa5a525da7602a Mon Sep 17 00:00:00 2001
From: "Alexander V. Nikolaev" <avn@avnik.info>
Date: Mon, 23 Mar 2020 01:47:12 +0200
Subject: [PATCH] nixos: Introduce nix.buildLocation option

Allow to specify where package build will happens.
It helps big packages (like browsers) not to overflow tmpfs.
---
 nixos/modules/services/misc/nix-daemon.nix | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/nixos/modules/services/misc/nix-daemon.nix b/nixos/modules/services/misc/nix-daemon.nix
index 0c2407e1dd2..022ddad8f36 100644
--- a/nixos/modules/services/misc/nix-daemon.nix
+++ b/nixos/modules/services/misc/nix-daemon.nix
@@ -430,6 +430,16 @@ in
         '';
       };
 
+      buildLocation = mkOption {
+        type = types.str;
+        default = "/tmp";
+        example = "/var/buildroot";
+        description = ''
+          Temporary directory, which used to unpack and build source packages.
+          (by default <filename>/tmp</filename> is used, which commonly reside on tmpfs,
+          and big packages (like browsers) can just not fit there)
+        '';
+      };
     };
 
   };
@@ -476,7 +486,9 @@ in
           ++ optionals cfg.distributedBuilds [ pkgs.gzip ];
 
         environment = cfg.envVars
-          // { CURL_CA_BUNDLE = "/etc/ssl/certs/ca-certificates.crt"; }
+          // { CURL_CA_BUNDLE = "/etc/ssl/certs/ca-certificates.crt";
+               TMPDIR = cfg.buildLocation;
+             }
           // config.networking.proxy.envVars;
 
         unitConfig.RequiresMountsFor = "/nix/store";
@@ -490,6 +502,8 @@ in
         restartTriggers = [ nixConf ];
       };
 
+    systemd.tmpfiles.rules = [ "d ${cfg.buildLocation} 0775 root root -" ];
+
     # Set up the environment variables for running Nix.
     environment.sessionVariables = cfg.envVars //
       { NIX_PATH = cfg.nixPath;