Root contexts (systemd services running as root, PID 1) default to
store=auto which resolves to the LOCAL nix store — bypassing the host
daemon, its remote builders (muede-pc2), and any prebuilt derivation
outputs already in the shared store. This causes spurious full
rebuilds of agent toplevels that the host already built and cached.
Two changes:
harness-base.nix:
- Add systemd.globalEnvironment.NIX_REMOTE = "daemon" — sets
DefaultEnvironment in systemd.conf so every unit in the container
inherits NIX_REMOTE=daemon. Non-root contexts already default to
the daemon socket; this only matters for root services that would
otherwise use the local store.
- Add NIX_REMOTE = "daemon" to environment.variables so interactive
shells also have it set (redundant with /etc/profile.d/nix-daemon.sh
but explicit and profile-agnostic).
hive-c0re.nix (hive-priv service):
- Add NIX_REMOTE = "daemon" to the service environment. hive-priv
runs as root and invokes nixos-container update + nix prebuild; these
must route through the host daemon so they see the shared store and
remote builders, not a private local store.
The sandbox-fallback = true in harness-base.nix is kept as a belt-
and-suspenders fallback but becomes a no-op for the common case once
nix routes through the daemon (the daemon builds on the host where
sandboxing works).
3a4b8d9873