My external hdd ony mounts with nix-rebuild switch

Help
1

I’m trying to create a very basic nas with nixos using an external hard disk I had lying around. This needs to be mounted at boot and preferably re-mounted if it gets disconnected then reconnected.

So far I’ve tried this config in my configuration.nix :
fileSystems."/mnt/ut3-drive" = {
device = "/dev/sdb"; # tried with /dev/by-uuid/... as well
fsType = "btrfs";
options = [
"x-systemd.automount"
"x-systemd.device-timeout=10s"
"nofail"
];
};
Which correctly mounts my disk after nixos-rebuild switch but not after reboot.
How can I make it mount automatically (like an entry in fstab) using nix config ?

2

FYI that’s never correct, always use unique IDs (by-label or by-uuid).

3

Thanks that makes sense, however as stated in my config snippet, I tried by uuid already with the uuid copied directly from lsblk so I heavily doubt that is the problem.