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GRUB image files

   GRUB consists of several images: two essential stages, optional
stages called "Stage 1.5", one image for bootable CD-ROM, and two
network boot images. Here is a short overview of them. *Note
Internals::, for more details.
     This is an essential image used for booting up GRUB. Usually, this
     is embedded in an MBR or the boot sector of a partition. Because a
     PC boot sector is 512 bytes, the size of this image is exactly 512
     All `stage1' must do is to load Stage 2 or Stage 1.5 from a local
     disk. Because of the size restriction, `stage1' encodes the
     location of Stage 2 (or Stage 1.5) in a block list format, so it
     never understand any filesystem structure.
     This is the core image of GRUB. It does everything but booting up
     itself. Usually, this is put in a filesystem, but that is not
     These are called "Stage 1.5", because they serve as a bridge
     between `stage1' and `stage2', that is to say, Stage 1.5 is loaded
     by Stage 1 and Stage 1.5 loads Stage 2. The difference between
     `stage1' and `*_stage1_5' is that the former doesn't understand
     any filesystem while the latter understands one filesystem (e.g.
     `e2fs_stage1_5' understands ext2fs). So you can move the Stage 2
     image to another location safely, even after GRUB has been
     While Stage 2 cannot generally be embedded in a fixed area as the
     size is so large, Stage 1.5 can be installed into the area right
     after an MBR, or the boot loader area of a ReiserFS or a FFS.
     This is a boot image for CD-ROMs using the "no emulation mode" in
     El Torito specification. This is identical to Stage 2, except that
     this boots up without Stage 1 and sets up a special drive `(cd)'.
     This is a network boot image for the Network Image Proposal used
     by some network boot loaders, such as Etherboot. This is mostly
     the same as Stage 2, but it also sets up a network and loads a
     configuration file from the network.
     This is another network boot image for the Preboot Execution
     Environment used by several Netboot ROMs. This is identical to
     `nbgrub', except for the format.