Migrate nix-auto-installer into this flake

Folds the separate nix-auto-installer repo's build outputs into this
flake so it can build every auto-installer artifact it used to,
negating the need for that repo:

- modules/installer/{common,iso,proxmox-lxc}.nix — migrated from
  nix-auto-installer's common.nix/installer.nix/proxmox-lxc.nix.
- flake.nix gains nixosConfigurations.{installer,proxmox-lxc} and
  packages.x86_64-linux.{iso,lxc,pxe,all}, matching the original
  repo's interface (nix build .#iso / .#lxc / .#pxe / .#all).
- Dropped the live Gitea PAT baked into every installer image via
  environment.etc."git-credentials" — gitea.lan.ddnsgeek.com/beatzaplenty/nixos.git
  allows anonymous read, so the installer (which only ever reads the
  flake, never pushes) doesn't need a credential at all.
- installer_old.nix wasn't migrated — dead code, unreferenced by the
  source repo's flake.nix, and carried a second stale leaked token.
- The installer environment's own hardcoded login password hash is
  preserved as-is: sops-nix has no stable per-boot host key to derive
  an age key from on ephemeral installer media, so it can't reuse the
  same per-host secret mechanism the rest of this repo uses without
  separate design work.
- vars.adminSshKey / vars.dockerHost-style dedup: the installer's SSH
  authorized key and its FLAKE_BASE_URL domain were exact duplicates
  of values already in variables.nix / modules/common/configuration.nix,
  so both now reference the single source of truth instead.

Verified eval-equivalent for every existing host (drvPath-identical)
and confirmed the migrated auto-install.sh script renders byte-for-byte
identical to the source repo's output.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01La55Nsss8jZ7ZuzUV9mfot

flake.nix

@@ -23,6 +23,7 @@
     let
       system = "x86_64-linux";
       inherit (nixpkgs) lib;
+      pkgs = nixpkgs.legacyPackages.${system};
       vars = import ./variables.nix;
 
       # Generates a nixosConfiguration from a platform (what it runs on) and
@@ -86,9 +87,65 @@
         lxc-pxe-boot = mkTarget { platform = "lxc"; buildType = "pxe-boot"; hostPath = ./hosts/pxe-boot/host.nix; };
       };
 
+      # Auto-install environments (migrated from the former nix-auto-installer
+      # flake): a self-contained NixOS installer that boots, discovers this
+      # flake's own nixosConfigurations over the network, and runs
+      # nixos-install against whichever one the operator picks. These are
+      # deliberately not part of the platform x build-type matrix above —
+      # they're throwaway boot media, not persistent hosts, so they skip
+      # disko/sops-nix/home-manager and just need `vars`.
+      installerTargets = {
+        installer = nixpkgs.lib.nixosSystem {
+          inherit system;
+          modules = [ ./modules/installer/iso.nix ];
+          specialArgs = { inherit vars; };
+        };
+
+        proxmox-lxc = nixpkgs.lib.nixosSystem {
+          inherit system;
+          modules = [ ./modules/installer/proxmox-lxc.nix ];
+          specialArgs = { inherit vars; };
+        };
+      };
+
+      # Same installer environment, built as netboot (kernel + initrd +
+      # iPXE script) instead of an ISO — this is what packages.pxe bundles.
+      netbootSystem = nixpkgs.lib.nixosSystem {
+        inherit system;
+        modules = [
+          ./modules/installer/iso.nix
+          ({ modulesPath, ... }: {
+            imports = [
+              (modulesPath + "/installer/netboot/netboot-minimal.nix")
+            ];
+          })
+        ];
+        specialArgs = { inherit vars; };
+      };
+
     in
     {
 
-      nixosConfigurations = generatedTargets;
+      nixosConfigurations = generatedTargets // installerTargets;
+
+      # Buildable auto-installer artifacts (`nix build .#<name>`), migrated
+      # unchanged from nix-auto-installer's interface.
+      packages.${system} = rec {
+        iso = installerTargets.installer.config.system.build.isoImage;
+
+        lxc = installerTargets.proxmox-lxc.config.system.build.tarball;
+
+        pxe = pkgs.linkFarm "pxe" [
+          { name = "netboot.ipxe"; path = netbootSystem.config.system.build.netbootIpxeScript; }
+          { name = "initrd"; path = netbootSystem.config.system.build.netbootRamdisk; }
+          { name = "kernel"; path = netbootSystem.config.system.build.kernel; }
+        ];
+
+        all = pkgs.linkFarm "all" [
+          { name = "iso"; path = iso; }
+          { name = "lxc"; path = lxc; }
+          { name = "pxe"; path = pxe; }
+        ];
+      };
     };
 }

modules/installer/common.nix

@@ -0,0 +1,202 @@
+{ pkgs, lib, vars, ... }:
+
+{
+  networking.useDHCP = lib.mkDefault true;
+
+  time.timeZone = vars.timeZone;
+
+  # Without this, the installer only ever sees cache.nixos.org, which
+  # doesn't carry sops-install-secrets (it's built straight from the
+  # sops-nix flake's own Go source, not part of nixpkgs) — every install
+  # would otherwise compile it from scratch, which is what ran an 8GB LXC
+  # container's disk out of space. Push a built copy to nix-cache once
+  # (from a machine with real disk headroom) and every future install,
+  # of any type, fetches instead of rebuilding.
+  nix.settings = {
+    substituters = [
+      "http://nix-cache"
+      "https://cache.nixos.org/"
+    ];
+    trusted-public-keys = [
+      "cache.local-1:usoWYanY3Kpq2+kDIS2nhWoLZiRxanmdysdzqCFBHW4="
+      "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+    ];
+  };
+
+  environment = {
+    systemPackages = with pkgs; [
+      git
+      curl
+      jq
+      parted
+      e2fsprogs
+      btrfs-progs
+      util-linux
+      disko
+    ];
+
+    # Write auto-install script to /root
+    etc."auto-install.sh" = {
+      text = ''
+            #!/run/current-system/sw/bin/bash
+            set -eux
+
+            set -euo pipefail
+
+        export FLAKE_BASE_URL="git+https://${vars.lanDomain}/beatzaplenty/nixos.git"
+
+        echo "Fetching available NixOS hosts from flake..."
+        mapfile -t options < <(
+          nix eval --json --no-use-registries --no-accept-flake-config --extra-experimental-features "flakes nix-command" \
+            "''${FLAKE_BASE_URL}#nixosConfigurations" \
+            --apply builtins.attrNames \
+          | jq -r '.[]'
+        )
+
+        if [[ ''${#options[@]} -eq 0 ]]; then
+          echo "ERROR: No NixOS hosts found in ''${FLAKE_BASE_URL}#nixosConfigurations" >&2
+          exit 1
+        fi
+
+        echo "Choose the flake profile to install:"
+        select choice in "''${options[@]}"; do
+          if [[ -n "$choice" ]]; then
+            echo "You selected: $choice"
+            break
+          else
+            echo "Invalid selection. Try again."
+          fi
+        done
+
+        echo "Starting install with flake: ''${FLAKE_BASE_URL}#''${choice}"
+
+        # Optional: confirm before proceeding
+        read -rp "Proceed with installation? (y/N): " confirm
+        if [[ ! "$confirm" =~ ^[Yy]$ ]]; then
+          echo "Aborted."
+          exit 1
+        fi
+
+        # A nix-cache host is *the* substituter/remote-builder for every other
+        # host once installed (its own config explicitly excludes itself from
+        # using either — see buildType != "nix-cache" in the nixos flake.nix).
+        # Installing one shouldn't depend on a nix-cache substituter either,
+        # for the same reason — plus in practice "nix-cache" only resolves over
+        # Tailscale, which a fresh installer environment was never connected to
+        # anyway, so it's dead weight even for non-nix-cache installs until
+        # that's sorted out. Override it away here specifically for nix-cache
+        # targets to keep install-time behaviour consistent with run-time.
+        nix_extra_opts=()
+        if [[ "''${choice}" == *-nix-cache ]]; then
+            echo "Installing a nix-cache host — skipping the nix-cache substituter."
+            nix_extra_opts+=(--option substituters "https://cache.nixos.org/")
+        fi
+
+        if nix eval --refresh --json  --extra-experimental-features "flakes nix-command" "''${nix_extra_opts[@]}" "''${FLAKE_BASE_URL}#nixosConfigurations.''${choice}.config.disko.devices.disk.main.device" >/dev/null 2>&1; then
+            disko --mode destroy,format,mount \
+                --flake "''${FLAKE_BASE_URL}#''${choice}" "''${nix_extra_opts[@]}" --yes
+        else
+            # No raw disk to partition — true for every LXC container, which has
+            # no block device visible from inside it, only its already-mounted
+            # root filesystem. nixos-install defaults to installing into /mnt; if
+            # nothing points /mnt at the real root, the new system gets built and
+            # written to a disconnected empty directory, never actually becomes
+            # bootable, and the container silently keeps running this installer
+            # environment forever. Bind-mount / onto /mnt so the install actually
+            # lands on the filesystem this container boots from.
+            echo "Selected host has no Disko configuration — installing in place via bind mount."
+            mount --bind / /mnt
+        fi
+
+        # sops-nix derives this host's decryption key from its own SSH host key
+        # at *activation* time, which runs before systemd would otherwise
+        # generate one on first boot. Without pre-seeding it here, secrets
+        # (including the login password) fail to decrypt on first boot.
+        # Generate the key + register it with `nixos`'s sops-nix setup ahead of
+        # time (see nix-auto-installer/scripts/prepare-host-key.sh), then scp it
+        # to /root/host-keys/ on this machine before continuing.
+        mkdir -p /root/host-keys
+        if [[ -f "/root/host-keys/''${choice}_ssh_host_ed25519_key" ]]; then
+            echo "Found pre-seeded SSH host key for ''${choice}, installing to target..."
+            install -D -m 0600 "/root/host-keys/''${choice}_ssh_host_ed25519_key" /mnt/etc/ssh/ssh_host_ed25519_key
+            install -D -m 0644 "/root/host-keys/''${choice}_ssh_host_ed25519_key.pub" /mnt/etc/ssh/ssh_host_ed25519_key.pub
+        else
+            echo "WARNING: no pre-seeded host key found at /root/host-keys/''${choice}_ssh_host_ed25519_key"
+            echo "sops-nix secrets (including the login password) will NOT decrypt on first boot."
+            echo "Run scripts/prepare-host-key.sh for host ''${choice} on your admin workstation first,"
+            echo "then scp the result here, if this host needs sops-nix secrets."
+            read -rp "Continue without a pre-seeded key anyway? (y/N): " skip_key
+            if [[ ! "$skip_key" =~ ^[Yy]$ ]]; then
+                echo "Aborted."
+                exit 1
+            fi
+        fi
+
+        mkdir -p /mnt/install-tmp
+        export TMPDIR=/mnt/install-tmp
+
+        nixos-install \
+            --flake "''${FLAKE_BASE_URL}#''${choice}" \
+            "''${nix_extra_opts[@]}" \
+            --no-root-password
+
+
+            rm -rf /mnt/install-tmp
+            # Redundant copy of the host's private key — the real one is now at
+            # /etc/ssh/ssh_host_ed25519_key. Nothing NixOS-managed ever cleans this
+            # up on its own since it was written imperatively, not declaratively.
+            rm -rf /root/host-keys
+            sleep 10
+            reboot
+      '';
+
+      mode = "0755";
+    };
+  };
+
+  programs.git.enable = true;
+
+  # Run the installer on first login. Previously this copied an /etc file
+  # into the nixos user's ~/.bash_profile via an activation script that
+  # got dropped in a refactor (and only ever worked for that one user
+  # anyway) — loginShellInit is NixOS's native hook for this, applies to
+  # any user's login shell (root included), and needs no home-directory
+  # file-copying/chown.
+  programs.bash.loginShellInit = ''
+    if [ -n "$PS1" ] && [ ! -e "$HOME/.auto_install_ran" ]; then
+      sudo /etc/auto-install.sh
+      touch "$HOME/.auto_install_ran"
+    fi
+  '';
+
+  services.openssh.enable = true;
+
+  services.openssh.settings = {
+    PermitRootLogin = "yes";
+    PasswordAuthentication = true;
+  };
+
+  users.users.root = {
+    hashedPassword =
+      "$6$Kwv9KAyvcurAViQF$H4.u3feqGE7lVoNgkFXhE3n2Pmo//9JYDTCz8ifrVHBxPjwa1xMby7tEZ8Bpt5MXs9Rkx6/YbZWxs5CpH0s/70";
+  };
+
+  users.users.${vars.primaryUser} = {
+    isNormalUser = true;
+
+    extraGroups = [
+      "wheel"
+    ];
+
+    shell = pkgs.bashInteractive;
+
+    hashedPassword =
+      "$6$Kwv9KAyvcurAViQF$H4.u3feqGE7lVoNgkFXhE3n2Pmo//9JYDTCz8ifrVHBxPjwa1xMby7tEZ8Bpt5MXs9Rkx6/YbZWxs5CpH0s/70";
+
+    openssh.authorizedKeys.keys = [
+      vars.adminSshKey
+    ];
+  };
+
+  system.stateVersion = "26.05";
+}

modules/installer/iso.nix

@@ -0,0 +1,8 @@
+{ modulesPath, ... }:
+
+{
+  imports = [
+    "${modulesPath}/installer/cd-dvd/installation-cd-minimal.nix"
+    ./common.nix
+  ];
+}

modules/installer/proxmox-lxc.nix

@@ -0,0 +1,12 @@
+{ modulesPath, ... }:
+
+{
+  imports = [
+    ./common.nix
+    (modulesPath + "/virtualisation/proxmox-lxc.nix")
+  ];
+
+  # LXC has no bootloader
+  boot.loader.grub.enable = false;
+  boot.loader.systemd-boot.enable = false;
+}

variables.nix

@@ -25,6 +25,10 @@
     "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIHxXTQxFnArK5HXG7czeoybZebCGfxpUdusJkPn+BCSp root@server"
   ];
 
+  # Admin SSH public key, authorized on the primary user of every host and
+  # the installer image's nixos/root users.
+  adminSshKey = "ssh-rsa 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 wayne@stream";
+
   # System
   timeZone = "Australia/Brisbane";
   primaryUser = "nixos"; # main interactive user on every host