nixos/hosts/common/optional/persistence.nix

{
  fileSystems."/persist".neededForBoot = true;
  environment.persistence."/persist" = {
    hideMounts = true;
    directories = [
      "/etc/nixos"
      "/srv"
      "/var/log"
      "/var/lib/nixos"
      "/var/lib/systemd/coredump"
      "/etc/NetworkManager/system-connections"
      "/var/lib/flatpak"
      "/run/secrets-for-users"
    ];
    files = [
      "/etc/ssh/ssh_host_ed25519_key"
      "/etc/ssh/ssh_host_ed25519_key.pub"
    ];
  };
}