Add configurationLimit to systemd-boot to prevent running out of disk space

Refs #23926

nixos/modules/system/boot/loader/systemd-boot/systemd-boot-builder.py

@@ -133,7 +133,9 @@ def get_generations(profile=None):
         universal_newlines=True)
     gen_lines = gen_list.split('\n')
     gen_lines.pop()
-    return [ (profile, int(line.split()[0])) for line in gen_lines ]
+
+    configurationLimit = @configurationLimit@
+    return [ (profile, int(line.split()[0])) for line in gen_lines ][-configurationLimit:]
 
 def remove_old_entries(gens):
     rex_profile = re.compile("^@efiSysMountPoint@/loader/entries/nixos-(.*)-generation-.*\.conf$")

nixos/modules/system/boot/loader/systemd-boot/systemd-boot.nix

@@ -22,7 +22,7 @@ let
 
     editor = if cfg.editor then "True" else "False";
 
-    inherit (cfg) consoleMode;
+    inherit (cfg) consoleMode configurationLimit;
 
     inherit (efi) efiSysMountPoint canTouchEfiVariables;
 
@@ -57,6 +57,16 @@ in {
       '';
     };
 
+    configurationLimit = mkOption {
+      default = 100;
+      example = 120;
+      type = types.int;
+      description = ''
+        Maximum of configurations in boot menu. Otherwise boot partition could
+        run out of disk space.
+      '';
+    };
+
     consoleMode = mkOption {
       default = "keep";