config/default.nix

@@ -4,4 +4,5 @@
     "${nixos-config}/services/tailscale.nix"
     ./systemd-boot.nix
   ];
+  boot.initrd.systemd.enable = true;
 }

modules/environment/impermanence.nix

@@ -17,30 +17,43 @@ with lib; {
       environment.impermanence = mkDefault (!config.boot.isContainer && !inTester);
     }
     (mkIf config.environment.impermanence {
-      boot.initrd.postDeviceCommands = mkAfter ''
+      boot.initrd.systemd.services.rootfs-cleanup = {
-        mkdir /btrfs_tmp
+        wantedBy = [
-        mount ${config.fileSystems."/".device} -t btrfs /btrfs_tmp
+          "initrd.target"
-        if [[ -e /btrfs_tmp/root ]]; then
+        ];
-          mkdir -p /btrfs_tmp/old_roots
+        after = [
-          timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
+          "initrd-root-device.target"
-          mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp
+        ];
-        fi
+        before = [
+          "sysroot.mount"
+        ];
+        unitConfig.DefaultDependencies = "no";
+        serviceConfig.Type = "oneshot";
+        script = ''
+          mkdir /btrfs_tmp
+          mount ${config.fileSystems."/".device} -t btrfs /btrfs_tmp
+          if [[ -e /btrfs_tmp/root ]]; then
+            mkdir -p /btrfs_tmp/old_roots
+            timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
+            mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp
+          fi
 
-        delete_subvolume_recursively() {
+          delete_subvolume_recursively() {
-          IFS=$'\n'
+            IFS=$'\n'
-          for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
+            for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
-            delete_subvolume_recursively "/btrfs_tmp/$i"
+              delete_subvolume_recursively "/btrfs_tmp/$i"
+            done
+            btrfs subvolume delete "$1"
+          }
+
+          for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
+            delete_subvolume_recursively "$i"
           done
-          btrfs subvolume delete "$1"
-        }
 
-        for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
+          btrfs subvolume create /btrfs_tmp/root
-          delete_subvolume_recursively "$i"
+          umount /btrfs_tmp
-        done
+        '';
-
+      };
-        btrfs subvolume create /btrfs_tmp/root
-        umount /btrfs_tmp
-      '';
       assertions = [
         {
           assertion = hasAttr "/" config.fileSystems;