ok- the main point with booting is thus- with the new raid code, you can
start raid from the kernel without any utils on the disk. meaning, all you
have to do is get the kernel into ram, and jump to its starting address.
this is what lilo is for, along with loadlin, etc.
they are needed cause the kernel, and esp. multiple kernels cant fit into
the MBR on the disk. so the mbr contains basically the CHS or linear
addresses of where the map file is, and thus the kernels. (simplified to
the point of incorrectness)
under RH, these all live in /boot, which is usually in the / partition.
you have a couple choices.
1. mkbootdisk. works well, i use it on some. makes setup simple, no
non-raid partitions, no multi-lilo.conf setups. but, it is the floppy, and
they suck for HA. (of course if ha is your deal, you have multiple
machines or multiple hardware raid adapters, etc)
2. small partitions at start of disk (within first 1024 Cyl) marked
bootable, mounted as /boot /boot1, etc. this requires some fooling with
lilo, etc, i used this on my latest box, works well (have floppy as
backup)
3. modify lilo to understand raid. this would be non-trivial for all
personalities except for raid1, as the actual kernel in those situations
will be split across disks, requiring lilo to know how to read the raid
superblocks, which is sometimes difficult, cause the superblock is at the
end of the disk, outside of the bios 1024 cyl range lilo has to use.
i had this working accidentally once. i setup lilo, somehow created an
array (raid1) using the root disk, without disturbing the data. the
kernels were
in the same CHS locations, and lilo still ran, even though it was a raid
partition. was impossible i thought, but neat! till i ran lilo again and
it bitched, could not upgrade!
the lilo option seems doable for raid1. hardware solutions are also
feasable, but non-trivial
al
"so don't tell us it can't be done, putting down what you don't know.
money isn't our god, integrity will free our souls" - Max Cavalera
