Node:Images, Next:Filesystem, Previous:Security, Up:Top
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. See Internals, for more details.
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, that is to say, Stage 1.5 is loaded by Stage 1 and Stage 1.5 loads Stage 2. The difference between
*_stage1_5is that the former doesn't understand any filesystem but the latter does an filesystem (e.g.
e2fs_stage1_5understands 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, except for the format.