So I opted to turn that into a systemd mount. In the spirit of “let’s write a blog post so that I don’t forget”, here’s how to do it.

Here’s the nix module. Replace the contents of let with your configuration. I’m mounting a b2 bucket, but this should work with another kind of remote.

{ pkgs, lib, ... }:
let
  mountPoint = "/mnt/where";
  remoteName = "rclone-remote-name";
  bucketName = "bucket-name";
  configFile = "/etc/rclone-mnt.conf";
in
{
  environment.systemPackages = with pkgs;[
    rclone
  ];
  systemd.mounts = lib.singleton {
    where = mountPoint;
    what = "${remoteName}:${bucketName}";
    type = "rclone";
    options = "_netdev,args2env,allow_other,vfs-cache-mode=full,config=${configFile}";
  };
  systemd.automounts = lib.singleton {
    where = mountPoint;
    wantedBy = [ "multi-user.target" ];
  };
}

And the contents of /etc/rclone-mnt.conf (not managed by nix to avoid secrets going to the store - I haven’t found a way for rclone to read the b2 key from a file).

[rclone-remote-name]
type = b2
hard_delete = True
account = 01234
key = 5678

With this in place, nixos will attempt to mount the remote when ready ("multi-user.target" - apparently you rarely want to use "default.target") and it knows that it requires network access (the "network-online.target" is implied by the pseudo option _netdev).