nixos/config: add defaultPackages option

readd perl (used in shell scripts), rsync (needed for NixOps) and strace (common debugging tool)

they where previously removed in NixOS#91213

Co-authored-by: Timo Kaufmann <timokau@zoho.com>
Co-authored-by: 8573 <8573@users.noreply.github.com>

nixos/modules/config/system-path.nix

@@ -43,6 +43,12 @@ let
  pkgs.which # 88K size
  ];
 
+ defaultPackages = map (pkg: setPrio ((pkg.meta.priority or 5) + 3) pkg)
+ [ pkgs.perl
+ pkgs.rsync
+ pkgs.strace
+ ];
+
 in
 
 {
@@ -65,6 +71,21 @@ in
  '';
  };
 
+ defaultPackages = mkOption {
+ type = types.listOf types.package;
+ default = defaultPackages;
+ example = literalExample "[]";
+ description = ''
+ Set of packages users expect from a minimal linux istall.
+ Like systemPackages, they appear in
+ /run/current-system/sw. These packages are
+ automatically available to all users, and are
+ automatically updated every time you rebuild the system
+ configuration.
+ If you want a more minimal system, set it to an empty list.
+ '';
+ };
+
  pathsToLink = mkOption {
  type = types.listOf types.str;
  # Note: We need `/lib' to be among `pathsToLink' for NSS modules
@@ -104,7 +125,7 @@ in
 
  config = {
 
- environment.systemPackages = requiredPackages;
+ environment.systemPackages = requiredPackages ++ config.environment.defaultPackages;
 
  environment.pathsToLink =
  [ "/bin"