03-Jun-2002
		Notes on booting arbitrary REAL mode
			binaries at 1000:0000


THIS IS NOT A PART OF THE STANDARD LILO DISTRIBUTION.

Arbitrary real mode binaries cannot be loaded directly by LILO.  However, if
they are made to look like a "kernel image loaded LOW," then LILO can be
induced to load them, thinking they are an out-of-date kernel image.

Such files are limited to 512K bytes; less if you have a very large Extended
BIOS Data Area (EBDA), which intrudes upon the 0x9000 segment.  The start
addresss of the file MUST be at offset 0 in the file.  It will be loaded at
0x1000:0000, and jumped to at that address (segment=0x1000, offset=0000) in
16-bit real mode.

In order to make the arbitrary binary, call it "foo.b", look like a kernel,
the file "pseudo.b", the pseudo kernel header, must be pre-pended; viz.,

	cat pseudo.b foo.b >foo.img

"foo.img" is the bootable pseudo-kernel.

In the configuration file, usually '/etc/lilo.conf', the following lines
must be added:

	image = foo.img
	    root = current

The root directory specification MUST be added (this is a "kernel" after
all), to avoid a fatal LILO error message (unspecified numeric value). 
Optionally, the arbitrary image may be given a name; viz.,

	    label = foo-test

The image should then be bootable from the LILO boot prompt.

EXAMPLE:  Add the LILO diagnostic program "test4.com" to the LILO boot menu.

The test program is created by "make floppy", which will write a floppy disk
image, but it also may be added to the LILO boot menu with the following
commands:

	make all
	cd diagnose
	make test4.com
	cd ..
	cat pseudo.b diagnose/test4.com >/boot/test4.img

Then append the following lines to '/etc/lilo.conf':

	image = /boot/test4.img
	  root = current
          label = diagnostic

Now, install the boot loader with the new menu item:

	/sbin/lilo

The last item on the boot menu should be "diagnostic", which will run
"test4.com" from the LILO boot prompt.

--John Coffman <johninsd@san.rr.com>
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