Export ZFS root pool before rebooting from the auto-installer

disko's --mode ...,mount leaves the pool imported (needed for
nixos-install to write into /mnt), and the script rebooted straight
into the newly-installed system without exporting it. That pool is
still stamped with the live installer's own hostid, which never
matches the target host's declared networking.hostId, and since
boot.zfs.forceImportRoot is false (the recommended setting, not a bug),
the first real boot refuses to force-import an unexported pool from a
different hostid -- which is exactly the ZFS-import stall baremetal-gui
was hitting after install. Exporting all pools right before reboot (a
no-op for non-ZFS hosts) clears the in-use state so import succeeds
regardless of hostid.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/installer/auto-install.sh

@@ -1,17 +1,20 @@
 #!/usr/bin/env nix-shell
-#!nix-shell -i bash -p jq disko nixos-install-tools
+#!nix-shell -i bash -p jq disko nixos-install-tools zfs
 # shellcheck shell=bash
 # The only genuinely external tools this script calls directly: `jq`
-# (parsing the `nix eval` host list) and `disko`/`nixos-install` (the
-# install itself). Everything disko shells out to internally
-# (parted/sgdisk/mkfs.*/zfs/...) is self-contained -- disko's own
-# generated scripts hardcode absolute Nix store paths for those, they
+# (parsing the `nix eval` host list), `disko`/`nixos-install` (the
+# install itself), and `zpool` (exporting a ZFS root pool before reboot,
+# see the comment above that call below). Everything disko shells out to
+# internally (parted/sgdisk/mkfs.*/zfs/...) is self-contained -- disko's
+# own generated scripts hardcode absolute Nix store paths for those, they
 # don't rely on this script's PATH at all (confirmed by inspecting a
 # generated system.build.formatScript). The built installer image
-# (modules/installer/common.nix) already has all three in
-# environment.systemPackages, so this nix-shell wrapper is a fast no-op
-# there; it's what makes the script also work standalone (e.g. run
-# directly from a checkout on a stock ISO), where they aren't.
+# (modules/installer/common.nix, plus the upstream
+# installation-cd-minimal.nix it imports via iso.nix) already has all
+# four in environment.systemPackages, so this nix-shell wrapper is a
+# fast no-op there; it's what makes the script also work standalone
+# (e.g. run directly from a checkout on a stock ISO), where they aren't
+# guaranteed.
 set -eux
 
 set -euo pipefail
@@ -162,5 +165,24 @@ nixos-install \
     # /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
+
+    # disko's --mode ...,mount left any ZFS root pool imported (that's what
+    # let nixos-install write into /mnt). If we reboot with it still
+    # imported, it isn't just "not exported" -- it's stamped with *this*
+    # live installer environment's hostid, which almost never matches the
+    # target's own networking.hostId (see hosts/*/host.nix; the installer
+    # itself sets none). modules/services/zfs/enable-service.nix and
+    # modules/common/configuration.nix both set boot.zfs.forceImportRoot =
+    # false deliberately (the safe option per that setting's own docs), so
+    # the freshly-installed system's first real boot sees a pool "in use by
+    # another system" and refuses to import it without -f -- which is what
+    # makes boot stall waiting on the ZFS import. Exporting here (a no-op
+    # if the chosen host has no ZFS root, e.g. proxmox-*/linode-*) clears
+    # that in-use state so the next import, from any hostid, succeeds.
+    if [[ -n "$(zpool list -H -o name 2>/dev/null)" ]]; then
+        echo "Exporting ZFS pool(s) before reboot..."
+        zpool export -a
+    fi
+
     sleep 10
     reboot