buildroot/fs/iso9660/Config.in

config BR2_TARGET_ROOTFS_ISO9660
	bool "iso image"
	depends on (BR2_i386 || BR2_x86_64)
	depends on BR2_LINUX_KERNEL
	depends on BR2_TARGET_GRUB || \
		BR2_TARGET_GRUB2 || \
		BR2_TARGET_SYSLINUX_ISOLINUX
	select BR2_LINUX_KERNEL_INSTALL_TARGET \
	       if (!BR2_TARGET_ROOTFS_ISO9660_INITRD && !BR2_TARGET_ROOTFS_INITRAMFS)
	help
	  Build a bootable ISO9660 image. By default, the root
	  filesystem is directly packed as the ISO9660 filesystem,
	  which means the root filesystem will be read-only. It
	  requires ISO9660 filesystem support and CDROM support in the
	  kernel.

	  However, if BR2_TARGET_ROOTFS_INITRAMFS or
	  BR2_TARGET_ROOTFS_ISO9660_INITRD have been enabled, the
	  ISO9660 filesystem will only contain a kernel image and
	  optionally an external initrd image. In this case, the
	  filesystem being in RAM, it will be read/write. No ISO9660
	  or CDROM support is needed in the kernel.

if BR2_TARGET_ROOTFS_ISO9660

choice
	prompt "Bootloader"

config BR2_TARGET_ROOTFS_ISO9660_GRUB
	bool "grub"
	depends on BR2_TARGET_GRUB
	select BR2_TARGET_GRUB_FS_ISO9660

config BR2_TARGET_ROOTFS_ISO9660_GRUB2
	bool "grub2"
	depends on BR2_TARGET_GRUB2
	help
	  Use Grub 2 as the bootloader for the ISO9660 image. Make
	  sure to enable the 'iso9660' module in
	  BR2_TARGET_GRUB2_BUILTIN_MODULES and to use 'cd' as the boot
	  partition in BR2_TARGET_GRUB2_BOOT_PARTITION=.

config BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
	bool "isolinux"
	depends on BR2_TARGET_SYSLINUX_ISOLINUX

endchoice

config BR2_TARGET_ROOTFS_ISO9660_BOOT_MENU
	string "Boot menu config file"
	default "fs/iso9660/menu.lst" if BR2_TARGET_ROOTFS_ISO9660_GRUB
	default "fs/iso9660/grub.cfg" if BR2_TARGET_ROOTFS_ISO9660_GRUB2
	default "fs/iso9660/isolinux.cfg" if BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
	help
	  Use this option to provide a custom bootloader configuration
	  file (menu.lst for Grub, grub.cfg for Grub 2, isolinux.cfg for
	  isolinux).

	  Note that the strings __KERNEL_PATH__ and __INITRD_PATH__
	  will automatically be replaced by the path to the kernel and
	  initrd images respectively.

config BR2_TARGET_ROOTFS_ISO9660_INITRD
	bool "Use initrd"
	default y
	select BR2_TARGET_ROOTFS_CPIO
	help
	  Enable this option to have the root filesystem bundled as an
	  initrd/initramfs rather than directly as the ISO9660
	  filesystem. With this option enabled, the ISO9660 will only
	  contain a kernel image, an initrd image (unless an initramfs
	  linked into the kernel is used) and the bootloader.

config BR2_TARGET_ROOTFS_ISO9660_HYBRID
	bool "Build hybrid image"
	depends on BR2_TARGET_ROOTFS_ISO9660_ISOLINUX
	help
	  Enable this option to build an hybrid image, i.e an image
	  which can either be booted from a CD-ROM or from a device
	  which BIOS considers a hard disk or ZIP disk, e.g. a USB key
	  or similar.

endif

comment "iso image needs a Linux kernel and one of grub, grub2 or isolinux to be built"
	depends on BR2_i386 || BR2_x86_64
	depends on !BR2_LINUX_KERNEL || \
		!(BR2_TARGET_GRUB || BR2_TARGET_GRUB2 || BR2_TARGET_SYSLINUX_ISOLINUX)