The Red Hat installer is based on the installer used in Red Hat's
Linux distributions for intel, sparc and alpha machines.  It provides
for installing from CD or local disk (either a MacOS HFS partition or
a Linux partition), or over the net by FTP or NFS.

The installer needs to be able to access two directories, called
`base' and `RPMS' respectively, in the same place.  The RPMS directory
contains RPM (Redhat Package Manager) packages for various pieces of
the system software.  The base directory contains sundry other files
used in the install process.

To run the installer, you boot `installer.coff', which contains a
Powermac/Linux kernel along with a pre-initialized ramdisk that
contains the installer program and assorted other files.  With both
the kernel image and the pre-initialized ramdisk stored in gzipped
form, the total comes to just under 1.4MB, which fits on a
high-density floppy.

The steps in the installation process are:

1.  Get the following files by FTP:

bootvars.sit.hqx        the Boot Variables application
installer.coff          the installer kernel image
                        ***make sure you get this in binary mode***

These are available from ftp://ftp.linuxppc.org/linuxppc/powermac or
from ftp://cap.anu.edu.au/pub/linux-pmac.

The Boot Variables application can conveniently be placed in the
Control Panels folder so you can invoke it from the apple menu.

2.  Copy installer.coff to a Mac-format floppy.  I suggest that you
use a fresh floppy, or a recently-reformatted one, because OF may have
trouble otherwise.  If the space on the floppy is too fragmented, OF
will give a `too many extents' error message and refuse to read it,
even though MacOS may have no difficulty.

3.  Open Boot Variables and set the boot-device variable to
`fd:installer.coff'.  It is also useful to set input-device and
output-device to allow you to see error messages from OF and/or talk
to OF's user interface if necessary.  The settings you use here will
depend on what sort of machine you have; section 2 gives more details.

4.  Press the `Write' button and then quit Boot Variables.

5.  Reboot.

6.  Insert the floppy containing installer.coff before the reset chord
finishes sounding.  If you don't insert it in time, OF will fail to
boot from the floppy.  In that case, just reset the machine again with
the command-option-power key combination.  You should hear the system
stepping through the floppy as it reads it - this will take a minute
or so.

7.  Following this, the screen should come up with the first screen of
the Red Hat installer.  The installer uses a series of screens with
menus, choices, buttons etc. to allow you to specify the details of
your installation.

N.B.: if you have any big-endian EXT2 partitions (from a previous
MkLinux or Powermac/Linux installation), *don't* specify them on the
screen labelled "Mount other partitions" (or some such).  The reason
is that the installer will label them "ext2" (rather than "bext2") and
the filesystem check on startup will damage them, since recent
versions of the ext2 filesystem check program cannot handle big-endian
ext2 filesystems correctly.

8.  At the end of the installation process, the last screen gives you
an opportunity to change the boot-device setting.  Set this to the OF
name for the disk containing your root partition (see section 2), or
to /AAPL,ROM if you wish to reboot MacOS at this stage.

9.  After the installer kernel shuts down, it is supposed to reset the
system, but it doesn't for some reason.  So you will need to reset it
manually with the command-option-power key combination.

Note: the installer boot floppy can also be used to rescue your Linux
installation if for some reason it gets into a state where it can't
boot.  You can boot from fd:installer.coff with boot-file set to
" --rescue".  When the kernel boots, it will start the installer which
will go through just the first few screens and then drop you into a
shell where you can mount your root partition and fix it up.
Alternatively, you can boot fd:installer.coff with boot-file set to
indicate your root partition (e.g. " root=/dev/sda6" or whatever).

        I have noted that on my 8600/250 the red hat style installer breaks when
there is more than 128 mgs of ram installed.  I believe the error is that 
root can't mount fs and you get a kernal panic when booting off the 
installer.coff floppy.
        You can install with 128 mgs or less and then insert extra 
ram after installation with no problems.

A bit of trivia for anyone who might be trying to build their own installer.coff, or any xcoff file with both a compressed kernel image and a compressed ramdisk image - apparently if the kernel is after the ramdisk, the zlib code in coffboot will fail to uncompress the kernel, and give an error like "inflate returned -3". You can use objcopy to remove the ramdisk image if it is before the kernel, and then reinsert it at the end. I don't know if this is true for all kernel versions, but I experienced it with both 2.1.124 and 2.2.1.