+ # Holds just a single file, rarely written, so
+ # use ext2, like was often used for the /boot partition.
+ # This exists because grub can only persist data to a non-cow fs.
+ # And we use persisting a var in grub to do a one time boot.
+ # We could pass the data on the kernel command line and persist it
+ # to grubenv after booting, but that relies on the boot always succeeding.
+ # This is just a bit more robust, and it could work for booting
+ # into ipxe which can't persist data, if we ever got that working.
+ mkfs.ext2 `grub_extdev`