Question about using btrfs-optin-persistence using systemd service about nix-config HOT 4 CLOSED

let
   rootfsDevice = "/dev/disk/by-label/${hostname}";
   wipeScript = ''
     counter=0

     # systemd initrd offers no way to hook in between
     # 'root device is ready' and 'mount the root device at /sysroot'.
     # Instead, lets poll for the root device.
     # https://github.com/systemd/systemd/issues/24904

     echo wipe: Waiting for ${rootfsDevice}
     while [ ! -e ${rootfsDevice} ]; do
       sleep 0.1
       counter=$((counter + 1))
       if [ $counter -ge 300 ]; then
           echo wipe: Timed out waiting for ${rootfsDevice}
           exit
       fi
     done
     echo wipe: Found ${rootfsDevice}. Wiping ephemeral.

     mkdir -p /btrfs
     mount -o subvol=/ ${rootfsDevice} /btrfs

     echo "Cleaning subvolume"
     btrfs subvolume list -o /btrfs/root | cut -f9 -d ' ' |
       while read subvolume; do
         btrfs subvolume delete "/btrfs/$subvolume"
       done && btrfs subvolume delete /btrfs/root

     echo "Restoring blank subvolume"
     btrfs subvolume snapshot /btrfs/root-blank /btrfs/root

     umount /btrfs
     rm -d /btrfs
   '';
in {
   options = {
     /* truncated */
   };
   config = {
     boot.initrd = {
       supportedFilesystems = [ "btrfs" ];
       systemd = {
         enable = true;
         emergencyAccess = true;
         initrdBin = with pkgs; [ coreutils btrfs-progs ];
         services.initrd-btrfs-root-wipe = {
           description = "Wipe ephemeral btrfs root";
           script = wipeScript;
           serviceConfig.Type = "oneshot";
           unitConfig.DefaultDependencies = "no";

           after = [ "cryptsetup.target" "initrd-root-device.target" ];
           before = [ "sysroot.mount" ];
           wantedBy = [ "sysroot.mount" ];
         };
       };
     };
   };

     /* truncated */
}