fixup! feat(extensions): add netboot extension for full TFTP+NFS boot

Author: iav

extensions/netboot/netboot.sh

@@ -3,7 +3,7 @@
 # Copyright (c) 2026 Igor Velkov
 # This file is a part of the Armbian Build Framework https://github.com/armbian/build/
 #
-# Netboot: produce kernel + DTB + extlinux.conf + rootfs.tgz for TFTP/NFS root
+# Netboot: produce kernel + DTB + extlinux.conf + rootfs archive/export tree for TFTP/NFS root
 # boot without local storage. See Developer-Guide_Netboot.md for server setup
 # (tftpd-hpa + nfs-kernel-server + router DHCP options) and for the
 # `netboot_artifacts_ready` hook used to auto-deploy artifacts to a server.
@@ -55,6 +55,9 @@ function extension_prepare_config__netboot_defaults_and_validate() {
 	else
 		declare -g NETBOOT_NFS_PATH="${NETBOOT_NFS_PATH:-/srv/netboot/rootfs/shared/${LINUXFAMILY}/${BOARD}/${BRANCH}-${RELEASE}}"
 	fi
+	if [[ "${NETBOOT_NFS_PATH}" != /* ]]; then
+		exit_with_error "${EXTENSION}: NETBOOT_NFS_PATH must be an absolute path (got '${NETBOOT_NFS_PATH}')"
+	fi
 
 	if [[ -n "${NETBOOT_CLIENT_MAC}" ]]; then
 		declare -g NETBOOT_CLIENT_MAC_NORMALIZED="${NETBOOT_CLIENT_MAC//:/-}"