Stuck on: `cp: cannot stat '/etc/ssh/ssh_host_ed25519_key': No such file or directory`

[uPaymeiFixit]

When running nixos-anywhere with my configuration, I always seem to get cp: cannot stat '/etc/ssh/ssh_host_ed25519_key': No such file or directory.

This seems to happen no matter what I do to the configuration, including which values I set in boot.initrd.network.ssh.hostKeys. For this example I've copied exactly the example configuration for Remote disk unlocking > Setup from the NixOS Wiki.

I can reproduce this when running either the nixos-installer-aarch64-linux.iso community image or the official minimal ISO image.

I'm new to nix, and even newer to nixos-anywhere, so it's entirely possible I've misunderstood how to use it correctly. I've tried a long list of things for the past two days and can't figure out how to get past this error. Any suggestions are greatly appreciated.

flake.nix

{
  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
  inputs.disko.url = "github:nix-community/disko";
  inputs.disko.inputs.nixpkgs.follows = "nixpkgs";

  outputs =
    { nixpkgs, disko, ... }:
    {
      nixosConfigurations.nixos-anywhere-bug = nixpkgs.lib.nixosSystem {

        system = "aarch64-linux";
        modules = [
          disko.nixosModules.disko
          {
            # Example from https://nixos.wiki/wiki/Remote_disk_unlocking
            boot.kernelParams = [ "ip=dhcp" ];
            boot.initrd = {
              availableKernelModules = [ "r8169" ];
              systemd.users.root.shell = "/bin/cryptsetup-askpass";
              network = {
                enable = true;
                ssh = {
                  enable = true;
                  port = 22;
                  authorizedKeys = [ "ssh-rsa AAAAyourpublic-key-here..." ];
                  hostKeys = [ "/etc/ssh/ssh_host_ed25519_key" ];
                };
              };
            };

            # Disko configuration
            boot.loader.grub.devices = [ "/dev/sda" ];
            disko.devices.disk.sda = {
              type = "disk";
              device = "/dev/sda";
              content = {
                type = "gpt";
                partitions = {
                  ESP = {
                    size = "500M";
                    type = "EF00";
                    content = {
                      type = "filesystem";
                      format = "vfat";
                      mountpoint = "/boot";
                    };
                  };
                  root = {
                    size = "100%";
                    content = {
                      type = "filesystem";
                      format = "ext4";
                      mountpoint = "/";
                    };
                  };
                };
              };
            };
          }
        ];
      };
    };
}

reproduce-bug.sh

#!/usr/bin/env bash

nix run github:nix-community/nixos-anywhere -- --no-reboot --flake .#nixos-anywhere-bug root@10.211.55.11

output

...
copying path '/nix/store/wr7w5dj4in81gcb2zhjl6h4v996q1q9m-linux-6.6.29-modules' from 'https://cache.nixos.org'...
### Installing NixOS ###
Warning: Permanently added '10.211.55.11' (ED25519) to the list of known hosts.
installing the boot loader...
setting up /etc...
updating GRUB 2 menu...
cp: cannot stat '/etc/ssh/ssh_host_ed25519_key': No such file or directory
failed to create initrd secrets No such file or directory
installation finished!
umount: /mnt/boot unmounted
umount: /mnt unmounted
### Done! ###

[phaer]

You can pre-generate ssh host keys locally and add them with --extra-files, or re-use ssh host keys from your existing linux install with --copy-host-keys. See https://nix-community.github.io/nixos-anywhere/howtos/secrets.html