Ok, uboot-n900-tools in the repo
/etc/default/u-boot-update-bootmenu
BOOTMENU_FAT_DIR="/media/sd-mmcblk1p1" BOOTMENU_CFG_DIR="/etc/bootmenu.d" BOOTMENU_BOOT_DIR="/boot" BOOTMENU_MAEMOBOOT_DIR="/maemo/boot" BOOTMENU_OPTBOOT_DIR="/media/sd-mmcblk1p2" BOOTMENU_TMP="/tmp"