From 814dbea27faaa9fa4d7b20541c23237b0a4a386f Mon Sep 17 00:00:00 2001
From: zowoq <59103226+zowoq@users.noreply.github.com>
Date: Mon, 6 Jul 2026 17:13:54 +1000
Subject: [PATCH 1/2] nixos/nspawn-container: hash name, remove assertion

the code comment is copied from the commit that added the assertion

https://github.com/NixOS/nixpkgs/commit/af0238c70efc80925c31d293da3bf8affca6437f
---
 .../nspawn-container/default.nix              | 28 -------------------
 .../run-nspawn/src/run_nspawn/__init__.py     |  8 ++++++
 2 files changed, 8 insertions(+), 28 deletions(-)

diff --git a/nixos/modules/virtualisation/nspawn-container/default.nix b/nixos/modules/virtualisation/nspawn-container/default.nix
index 82a06929e925..621f2bcb9f33 100644
--- a/nixos/modules/virtualisation/nspawn-container/default.nix
+++ b/nixos/modules/virtualisation/nspawn-container/default.nix
@@ -81,34 +81,6 @@ in
           which is prohibited within the Nix build sandbox where the test is run.
         '';
       }
-      {
-        # Check every interface defined in allInterfaces.
-        # Containers try to create a bridge "${config.system.name}-${interfaceName}"
-        assertion = lib.all (
-          iface:
-          let
-            hostName = "${config.system.name}-${iface.name}";
-          in
-          lib.stringLength hostName <= 15
-        ) (lib.attrValues cfg.allInterfaces);
-
-        message =
-          let
-            offendingInterfaces = lib.filter (
-              iface: lib.stringLength "${config.system.name}-${iface.name}" > 15
-            ) (lib.attrValues cfg.allInterfaces);
-            offenderList = map (
-              i:
-              "${config.system.name}-${i.name} (${toString (lib.stringLength "${config.system.name}-${i.name}")} chars)"
-            ) offendingInterfaces;
-          in
-          ''
-            The following generated host interface names exceed the Linux 15-character limit:
-              ${lib.concatStringsSep "\n            " offenderList}
-
-            Please shorten 'config.system.name' or the interface names in 'virtualisation.interfaces'.
-          '';
-      }
     ];
 
     virtualisation.systemd-nspawn.options = [
diff --git a/nixos/modules/virtualisation/nspawn-container/run-nspawn/src/run_nspawn/__init__.py b/nixos/modules/virtualisation/nspawn-container/run-nspawn/src/run_nspawn/__init__.py
index f733ad1845c4..9d5d73433e66 100644
--- a/nixos/modules/virtualisation/nspawn-container/run-nspawn/src/run_nspawn/__init__.py
+++ b/nixos/modules/virtualisation/nspawn-container/run-nspawn/src/run_nspawn/__init__.py
@@ -1,6 +1,7 @@
 import contextlib
 import dataclasses
 import fcntl
+import hashlib
 import logging
 import os
 import signal
@@ -124,6 +125,13 @@ def mk_veth(
     vlan: int,
 ) -> typing.Generator[None, None, None]:
     host_intf_name = f"{container_name}-{container_intf_name}"
+    # If the names for systemd-nspawn containers are too long,
+    # the generated bridge interface names will surpass the
+    # kernel limit IFNAMSIZ (15 characters + '\0').
+    if len(host_intf_name) > 15:
+        hashed = hashlib.sha256(host_intf_name.encode()).hexdigest()[:6]
+        host_intf_name = f"{host_intf_name[:8]}-{hashed}"
+
     with ensure_vlan_bridge(vlan) as bridge_name:
         logger.info("creating interface %s", host_intf_name)
         run_ip(

From 2e6f5555de91951c95a1d5010b92b2edf6da2ea6 Mon Sep 17 00:00:00 2001
From: zowoq <59103226+zowoq@users.noreply.github.com>
Date: Tue, 7 Jul 2026 10:20:12 +1000
Subject: [PATCH 2/2] nixosTests.grafana: switch to nspawn containers

---
 nixos/tests/grafana/basic.nix             | 4 ++--
 nixos/tests/grafana/provision/default.nix | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/nixos/tests/grafana/basic.nix b/nixos/tests/grafana/basic.nix
index eb024be44fa9..2221960135c5 100644
--- a/nixos/tests/grafana/basic.nix
+++ b/nixos/tests/grafana/basic.nix
@@ -84,7 +84,7 @@ import ../make-test-python.nix (
       };
     };
 
-    nodes = builtins.mapAttrs (
+    containers = builtins.mapAttrs (
       _: val:
       mkMerge [
         val
@@ -97,7 +97,7 @@ import ../make-test-python.nix (
 
     meta.maintainers = [ ];
 
-    inherit nodes;
+    inherit containers;
 
     testScript = ''
       start_all()
diff --git a/nixos/tests/grafana/provision/default.nix b/nixos/tests/grafana/provision/default.nix
index 8fed76d5b282..9109aa58a99a 100644
--- a/nixos/tests/grafana/provision/default.nix
+++ b/nixos/tests/grafana/provision/default.nix
@@ -183,7 +183,7 @@ import ../../make-test-python.nix (
         };
     };
 
-    nodes = builtins.mapAttrs (
+    containers = builtins.mapAttrs (
       _: val:
       mkMerge [
         val
@@ -196,7 +196,7 @@ import ../../make-test-python.nix (
 
     meta.maintainers = [ ];
 
-    inherit nodes;
+    inherit containers;
 
     testScript = ''
       start_all()