From 48fcf9307624388d555e82584eb0c477841c6cb2 Mon Sep 17 00:00:00 2001
From: Martin Fischer <martin@push-f.com>
Date: Sat, 20 Sep 2025 12:51:20 +0200
Subject: fix: make rebuild register host-specific gcroots

---
 nixos/.gitignore |  2 +-
 nixos/rebuild    | 15 ++++++++++-----
 2 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/nixos/.gitignore b/nixos/.gitignore
index c4a847d..06d39e8 100644
--- a/nixos/.gitignore
+++ b/nixos/.gitignore
@@ -1 +1 @@
-/result
+/hosts/*/result
diff --git a/nixos/rebuild b/nixos/rebuild
index d902bd8..9e62b33 100755
--- a/nixos/rebuild
+++ b/nixos/rebuild
@@ -23,8 +23,13 @@ nixpkgsPath=$(
     '
 )
 
-# FIXME: change into host directory for host-specific garbage collector roots
-cd "$top"
-# nixos-rebuild always reads Nixpkgs from the NIX_PATH,
-# so we need to set it explicitly to our pinned version
-exec nixos-rebuild "$@" -I nixpkgs="$nixpkgsPath" -I nixos-config="$configPath" -I top="$top"
+(
+  # The result symlink created in the current directory is registered as a root of the Nix
+  # garbage collector, so it's important that we call nixos-rebuild from the host directory.
+  # (nix-build has an --out-link option but that option cannot be set via nixos-rebuild).
+  cd $top/hosts/$HOSTNAME &&
+
+  # nixos-rebuild always reads Nixpkgs from the NIX_PATH,
+  # so we need to set it explicitly to our pinned version
+  exec nixos-rebuild "$@" -I nixpkgs="$nixpkgsPath" -I nixos-config="$configPath" -I top="$top"
+)
-- 
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