(GNU/Linux): Update for GRUB 2.
(Serial terminal): Remove mention of --disable-serial, which was a
GRUB Legacy configure option. Update instructions to use
`terminal_input' and `terminal_output' rather than `terminal'.
(Vendor power-on keys): Copy-edit. Add cross-references to `Simple
configuration' and `Installing GRUB using grub-install'.
(Menu entry editor): Update for GRUB 2.
(terminfo): Add vt100-color, ieee1275, and dumb terminal types.
Document new -a, -u, and -v options.
(initrd): New section.
(initrd16): New section.
(linux): New section.
(linux16): New section.
(search): The `var' argument to `--set' is optional.
(GRUB only offers a rescue shell): Go into a little more detail on
drive ordering.
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