From 603813ee37b9a1298208fe37eab5f0b919b2d6e4 Mon Sep 17 00:00:00 2001
From: danjujan <44864658+danjujan@users.noreply.github.com>
Date: Wed, 4 Dec 2024 20:41:42 +0100
Subject: [PATCH 1/3] make-disk-image: improve xargs invocation

---
 lib/make-disk-image.nix | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/make-disk-image.nix b/lib/make-disk-image.nix
index be491f7b..367eae4f 100644
--- a/lib/make-disk-image.nix
+++ b/lib/make-disk-image.nix
@@ -94,7 +94,7 @@ let
 
     # We copy files with cp because `nix copy` seems to have a large memory leak
     mkdir -p ${systemToInstall.config.disko.rootMountPoint}/nix/store
-    xargs cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store < ${closureInfo}/store-paths
+    xargs -P 0 -I {} sh -c 'cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store "$1" || exit 255' sh {} < ${closureInfo}/store-paths
 
     ${systemToInstall.config.system.build.nixos-install}/bin/nixos-install --root ${systemToInstall.config.disko.rootMountPoint} --system ${systemToInstall.config.system.build.toplevel} --keep-going --no-channel-copy -v --no-root-password --option binary-caches ""
     umount -Rv ${systemToInstall.config.disko.rootMountPoint}

From e6c2ca8c24a1a30ef24e5856436360a1db84a197 Mon Sep 17 00:00:00 2001
From: danjujan <44864658+danjujan@users.noreply.github.com>
Date: Thu, 5 Dec 2024 18:32:18 +0100
Subject: [PATCH 2/3] make-disk-image: save xargs invocation overhead

---
 lib/make-disk-image.nix | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/lib/make-disk-image.nix b/lib/make-disk-image.nix
index 367eae4f..313ce16f 100644
--- a/lib/make-disk-image.nix
+++ b/lib/make-disk-image.nix
@@ -87,14 +87,21 @@ let
     ${lib.getExe systemToInstall.config.system.build.destroyFormatMount} --yes-wipe-all-disks
   '';
 
-  installer = lib.optionalString cfg.copyNixStore ''
+  installer =
+    let
+      # let xargs stop directly when cp fails
+      cpEarlyExit = pkgs.writeScript "cp-early-exit" ''
+        cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store "$@" || exit 255
+      '';
+    in
+    lib.optionalString cfg.copyNixStore ''
     # populate nix db, so nixos-install doesn't complain
     export NIX_STATE_DIR=${systemToInstall.config.disko.rootMountPoint}/nix/var/nix
     nix-store --load-db < "${closureInfo}/registration"
 
     # We copy files with cp because `nix copy` seems to have a large memory leak
     mkdir -p ${systemToInstall.config.disko.rootMountPoint}/nix/store
-    xargs -P 0 -I {} sh -c 'cp --recursive --target ${systemToInstall.config.disko.rootMountPoint}/nix/store "$1" || exit 255' sh {} < ${closureInfo}/store-paths
+    xargs -P 0 ${cpEarlyExit} < ${closureInfo}/store-paths
 
     ${systemToInstall.config.system.build.nixos-install}/bin/nixos-install --root ${systemToInstall.config.disko.rootMountPoint} --system ${systemToInstall.config.system.build.toplevel} --keep-going --no-channel-copy -v --no-root-password --option binary-caches ""
     umount -Rv ${systemToInstall.config.disko.rootMountPoint}

From 472e4d537c7591f184e904af1e67d0f6eeae7531 Mon Sep 17 00:00:00 2001
From: danjujan <44864658+danjujan@users.noreply.github.com>
Date: Fri, 6 Dec 2024 16:17:25 +0100
Subject: [PATCH 3/3] make-disk-image: make xargs flags configurable

---
 lib/make-disk-image.nix | 2 +-
 module.nix              | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/lib/make-disk-image.nix b/lib/make-disk-image.nix
index 313ce16f..409bd046 100644
--- a/lib/make-disk-image.nix
+++ b/lib/make-disk-image.nix
@@ -101,7 +101,7 @@ let
 
     # We copy files with cp because `nix copy` seems to have a large memory leak
     mkdir -p ${systemToInstall.config.disko.rootMountPoint}/nix/store
-    xargs -P 0 ${cpEarlyExit} < ${closureInfo}/store-paths
+    xargs ${cfg.xargsFlags} ${cpEarlyExit} < ${closureInfo}/store-paths
 
     ${systemToInstall.config.system.build.nixos-install}/bin/nixos-install --root ${systemToInstall.config.disko.rootMountPoint} --system ${systemToInstall.config.system.build.toplevel} --keep-going --no-channel-copy -v --no-root-password --option binary-caches ""
     umount -Rv ${systemToInstall.config.disko.rootMountPoint}
diff --git a/module.nix b/module.nix
index 6543e111..3f213c3c 100644
--- a/module.nix
+++ b/module.nix
@@ -102,6 +102,13 @@ in
         description = "QEMU image format to use for the disk images";
         default = "raw";
       };
+
+      xargsFlags = lib.mkOption {
+        type = lib.types.str;
+        description = "flags for xargs invocation";
+        default = "";
+        example = "-L 100 -P 0";
+      };
     };
 
     memSize = lib.mkOption {