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(grub.info)Images

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GRUB image files
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   GRUB consists of several images: two essential stages, optional
stages called "Stage 1.5", and two network boot images. Here is a short
overview of them. Note: Internals, for more details.

`stage1'
     This is an essential image used for booting up GRUB. Usually, this
     is embedded in a MBR or the boot sector of a partition. Because a
     PC boot sector is 512 bytes, the size of this image is exactly 512
     bytes.

     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.

`stage2'
     This is the core image of GRUB. This does all things but booting up
     itself. Usually, this is put in a filesystem, but that is not
     required.

`e2fs_stage1_5'
`fat_stage1_5'
`ffs_stage1_5'
`jfs_stage1_5'
`minix_stage1_5'
`reiserfs_stage1_5'
`vstafs_stage1_5'
`xfs_stage1_5'
     These are called "Stage 1.5", because the purpose is 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 but the latter does an filesystem (e.g.
     `e2fs_stage1_5' understands ext2fs). So you can move the location
     of Stage 2 to another safely, even after GRUB has been installed.

     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 a MBR, or the boot loader area of a ReiserFS or a FFS.

`nbgrub'
     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 this also sets up a network and loads a
     configuration file from the network.

`pxegrub'
     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.