Fix Limine install with ESP mounted outside /boot

Place limine.conf next to the EFI binary on the ESP so it is found
regardless of ESP mountpoint, and block unbootable layouts (non-UKI
Limine with ESP not at /boot and no separate /boot partition) in
GlobalMenu validation, guided.main() and _add_limine_bootloader().

Fixes #4333

archinstall/lib/global_menu.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 from typing import override
 
 from archinstall.default_profiles.profile import GreeterType
@@ -492,6 +493,11 @@ class GlobalMenu(AbstractMenu[None]):
 		if bootloader == Bootloader.Limine:
 			if boot_partition.fs_type not in [FilesystemType.FAT12, FilesystemType.FAT16, FilesystemType.FAT32]:
 				return 'Limine does not support booting with a non-FAT boot partition'
+			if self._uefi and efi_partition and boot_partition == efi_partition and efi_partition.mountpoint != Path('/boot') and not bootloader_config.uki:
+				return (
+					f'Limine requires kernels on a FAT partition. The ESP is mounted at {efi_partition.mountpoint}, '
+					'enable UKI or add a separate /boot partition'
+				)
 
 		elif bootloader == Bootloader.Refind:
 			if not self._uefi:

archinstall/lib/installer.py

@@ -1466,6 +1466,16 @@ class Installer:
 			elif not efi_partition.mountpoint:
 				raise ValueError('EFI partition is not mounted')
 
+			# Limine can only read FAT filesystems. When the ESP doubles as
+			# the boot partition but is mounted outside /boot (e.g. /efi,
+			# /boot/efi) and UKI is disabled, kernels end up on the root
+			# filesystem under /boot/ which Limine cannot access.
+			if boot_partition == efi_partition and efi_partition.mountpoint != Path('/boot') and not uki_enabled:
+				raise DiskError(
+					f'Limine requires kernels on a FAT partition. The ESP is mounted at {efi_partition.mountpoint}, '
+					'so enable UKI or add a separate /boot partition to install Limine.',
+				)
+
 			info(f'Limine EFI partition: {efi_partition.dev_path}')
 
 			parent_dev_path = get_parent_device_path(efi_partition.safe_dev_path)
@@ -1476,15 +1486,11 @@ class Installer:
 				if bootloader_removable:
 					efi_dir_path = efi_dir_path / 'BOOT'
 					efi_dir_path_target = efi_dir_path_target / 'BOOT'
-
-					boot_limine_path = self.target / 'boot' / 'limine'
-					boot_limine_path.mkdir(parents=True, exist_ok=True)
-					config_path = boot_limine_path / 'limine.conf'
 				else:
 					efi_dir_path = efi_dir_path / 'arch-limine'
 					efi_dir_path_target = efi_dir_path_target / 'arch-limine'
 
-					config_path = efi_dir_path / 'limine.conf'
+				config_path = efi_dir_path / 'limine.conf'
 
 				efi_dir_path.mkdir(parents=True, exist_ok=True)
 

archinstall/scripts/guided.py

@@ -1,6 +1,7 @@
 import os
 import sys
 import time
+from pathlib import Path
 
 from archinstall.lib.applications.application_handler import ApplicationHandler
 from archinstall.lib.args import ArchConfig, ArchConfigHandler
@@ -195,6 +196,35 @@ def perform_installation(
 						pass
 
 
+def _check_bootloader_layout(config: ArchConfig) -> str | None:
+	"""Validate bootloader configuration against disk layout.
+
+	Returns an error message if the configuration would produce an
+	unbootable system, or None if it is valid.
+	"""
+	# Limine can only read FAT. When the ESP is the boot partition but
+	# mounted outside /boot and UKI is disabled, the kernel ends up on the
+	# root filesystem which Limine cannot access.
+	if not (config.bootloader_config and config.bootloader_config.bootloader == Bootloader.Limine and not config.bootloader_config.uki and config.disk_config):
+		return None
+
+	efi_part = next(
+		(p for m in config.disk_config.device_modifications if (p := m.get_efi_partition())),
+		None,
+	)
+	boot_part = next(
+		(p for m in config.disk_config.device_modifications if (p := m.get_boot_partition())),
+		None,
+	)
+
+	if efi_part and boot_part == efi_part and efi_part.mountpoint != Path('/boot'):
+		return (
+			f'Limine requires kernels on a FAT partition. The ESP is mounted at {efi_part.mountpoint}, '
+			'enable UKI or add a separate /boot partition to install Limine.'
+		)
+	return None
+
+
 def main(arch_config_handler: ArchConfigHandler | None = None) -> None:
 	if arch_config_handler is None:
 		arch_config_handler = ArchConfigHandler()
@@ -211,6 +241,12 @@ def main(arch_config_handler: ArchConfigHandler | None = None) -> None:
 	config.write_debug()
 	config.save()
 
+	# Safety net for silent/config-file flow. The TUI menu blocks Install via
+	# GlobalMenu._validate_bootloader() before reaching this point.
+	if err_msg := _check_bootloader_layout(arch_config_handler.config):
+		error(err_msg)
+		return
+
 	if arch_config_handler.args.dry_run:
 		return