Re: bootable, rootable, base, and the rest
"A. P. Harris" <apharris@queso.onshore.com> writes:
> Regarding the state of the boot floppies, I think most of the
> structure is already there. It seems to me that there could be
> more shared logic between some of the components (i.e., building the
> driver disk and the rescue disk scripts).
(Once I tried to follow this logic in the original documentation, but
there weren't that many architectures at that time.)
> * rootability -- loading the root file system. We currently have
> this in the root.bin .
> media: rescue disk or separate root disk, CD, TFTP
>
> current limitations:
>
> - we think we want both a 2.8MB option as well as 1.4MB
> - we don't support root on a number of more exotic media,
> such as PCMCIA floppy, ZIP drive, LS120
> - the need to support new root.bin media would drive us to
> create an initrd
Basically the difference is that you use a whole floppy disk for a
root fs, but you don't want to allocate a whole ZIP or CD for this.
So we need a way to tell the kernel which part of the medium should be
loaded.
Options:
a) Load a file from a file system on that medium.
b) Load a sequence of blocks from that medium.
Option b) was used on RedHat install floppies, it seems to be a
not-so-well-known kernel feature. No idea whether it works on other
media.
Option a) isn't implemented. Without kernel support we need a small
initrd that mounts the medium, initialises the ramdisk from that
medium and uses this ramdisk as root.
(A variant is to construct the filesystem in a way that the fs mounted
from the medium can be readonly. Then you can simply loop-mount it
into the already-existing fs.)
Sven
--
Sven Rudolph <sr1@sax.de> http://www.sax.de/~sr1/
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