{ ... }: {
  # machine-id is used by systemd for the journal, if you don't
  # persist this file you won't be able to easily use journalctl to
  # look at journals for previous boots.
  environment.etc."machine-id".source = "/nix/persist/etc/machine-id";


  # if you want to run an openssh daemon, you may want to store the
  # host keys across reboots.
  #
  # For this to work you will need to create the directory yourself:
  # $ mkdir /nix/persist/etc/ssh
  environment.etc."ssh/ssh_host_rsa_key".source = "/nix/persist/etc/ssh/ssh_host_rsa_key";
  environment.etc."ssh/ssh_host_rsa_key.pub".source = "/nix/persist/etc/ssh/ssh_host_rsa_key.pub";
  environment.etc."ssh/ssh_host_ed25519_key".source = "/nix/persist/etc/ssh/ssh_host_ed25519_key";
  environment.etc."ssh/ssh_host_ed25519_key.pub".source = "/nix/persist/etc/ssh/ssh_host_ed25519_key.pub";

}