From f6d03359b3810dca112e1190eeec7f18a3bab247 Mon Sep 17 00:00:00 2001
From: Moritz Ulrich <moritz@tarn-vedra.de>
Date: Thu, 5 Jun 2014 18:38:38 +0200
Subject: [PATCH] Only overwrite container-configuration when --config is
 specified.

Fixes #2834.
---
 nixos/modules/virtualisation/nixos-container.pl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/nixos/modules/virtualisation/nixos-container.pl b/nixos/modules/virtualisation/nixos-container.pl
index 718630fe8b9b..5083abd84489 100644
--- a/nixos/modules/virtualisation/nixos-container.pl
+++ b/nixos/modules/virtualisation/nixos-container.pl
@@ -31,7 +31,7 @@ EOF
 }
 
 my $ensureUniqueName = 0;
-my $extraConfig = "";
+my $extraConfig;
 
 GetOptions(
     "help" => sub { showHelp() },
@@ -190,7 +190,7 @@ elsif ($action eq "update") {
 
     # FIXME: may want to be more careful about clobbering the existing
     # configuration.nix.
-    writeNixOSConfig $nixosConfigFile if defined $extraConfig;
+    writeNixOSConfig $nixosConfigFile if (defined $extraConfig && $extraConfig ne "");
 
     system("nix-env", "-p", "$profileDir/system",
            "-I", "nixos-config=$nixosConfigFile", "-f", "<nixpkgs/nixos>",