There is a definite void in the official documentation available for getting 
linux up and running.  All of the documentation I've seen appears to be too 
vague for those of us not intimately familiar with yaboot, linux, partitions, 
PRAM, etc.  This document is my attempt to fill in some details that other 
resources have ALL omitted.  It is the result of days of frustrating trial and 
error on my part and is intended to spare others some of that frustration.

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    PART 1 - General Information
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This document describes the steps and pitfalls that you may face while trying to 
install Linux PPC 2K on an iBook.

First some terminology rules:
a) [mac-mac] = Mac OS Partition Number to Boot into Mac OS.
b) [mac-yaboot] = Mac OS Partition Number to Boot into yaboot
c) [linux-root] = Linux Partition Number containing installed linux stuff
d) [linux-swap] = Linux Partition Number containing the Linux Swap space

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    PART 2 - Getting Linux Up and Running (Pitfalls and Steps)
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1) Pitfall: [mac-yaboot] partition MUST BE AN HFS NOT AN HFS+ PARTITION!!!

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2) Pitfall: The kernel that came on the CD freezes on boot on iBook SE.  You 
must acquire a new, later kernel.  Try here http://ppclinux.apple.com/~benh/

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3) Pitfall: The kernel file must be uncompressed (converted from vmlinux...gz to 
just vmlinux...)

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4) Pitfall: The kernel (e.g. vmlinux-2.2.15pre14) must be just inside the [mac-
yaboot] hard drive icon.  DO NOT put it inside the system folder or any other 
folder.  For example, if your [mac-yaboot] partition is called "Linux Boot" then 
the path to the linux kernel should be

    "Linux Boot:vmlinux-2.2.15pre14".

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5) Pitfall: The yaboot.conf file is VERY sensitive and VERY UNDOCUMENTED.  All 
that I know is this:
  a) device=hd:   appears to be necessary

  b) default=[label] specifies which of the configurations will be run if you 
just hit enter at the initial yaboot prompt or don't respond within the 
specified timeout time.

  c) timeout=[time]  where time is specified in 1/10ths of seconds (e.g. 50 
means 5 seconds 55 means 5 1/2 seconds).  This timeout specifies how long yaboot 
will wait at the initial prompt before attempting to load the configuration 
specified by the "default" label above.

NOTE:  The header (containing the above 3 options) is separated from the 
configurations (containing the following options) by an empty line.  Each 
configuration is separated from the next by an empty line as well.

  d) If anything is wrong in the configuration you get the "image not found" (or 
something like that) error

  e) the video option in a given configuration is used to tell the kernel to use 
video hardware acceleration.  Specifying "novideo" means NO VIDEO ACCELERATION, 
NOT NO VIDEO AT ALL.

  f) There are other configuration options that must be specified for the 
installation ram disk, but for booting AFTER installation you only need 
"image=", "label=", "root=" and "novideo".

  g) 'image' has the syntax:  "image=hd:[yaboot partition #],[kernel name]".  
For example:
    image=hd:12,vmlinx-2.2.15pre14

  h) 'label' is a string describing the configuration being defined.  Examples 
are:  'lable=linux', 'label=install', 'label=ramdisk', etc.

  i) 'root' has the syntax: "root=/dev/hda[linux root partition #]".  For 
example:
    root=/dev/hda13

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6) Step: Partition your drive as specified in the documentation.  You need at 
least the following 4:

**** IMPORTANT *****
MAKE SURE THE [mac-mac] PARTITION IS BEFORE THE OTHER ONES.  THAT IS IMPORTANT 
FOR GETTING BACK TO MACOS AFTER YOU SET THINGS UP TO BOOT INTO LINUX!!!
**** IMPORTANT *****

  a) [mac-mac] (perhaps 2 Gb.  Type: HFS or HFS+, doesn't matter) - Contains 
MacOS and All Mac Utilities.

  b) [mac-yaboot] (perhaps 100 Mb. Type: HFS.  DO NOT CREATE THIS AS HFS+) - 
Contains yaboot, yaboot.conf and vmlinux kernels

  c) [linux-root] (perhaps 2 Gb.  Type: AUX) - Contains linux

  d) [linux-swap] (perhaps 100 Mb. Type: SWAP) - Contains swap space for linux.

**** IMPORTANT *****
MAKE SURE THE [mac-mac] PARTITION IS BEFORE THE OTHER ONES.  THAT IS IMPORTANT 
FOR GETTING BACK TO MACOS AFTER YOU SET THINGS UP TO BOOT INTO LINUX!!!
**** IMPORTANT *****

The astute reader will notice that this only accounts for around 4.2 Gb of the 6 
Gb (or more if you upgraded) of disk space you have.  You can distribute the 
remaining space however you want amongst these partitions.  (NOTE: I think the 
limit for swap space that linux will use is 128 Mb so don't bother making the 
[linux-swap] bigger than that).  If you like you can even create a new 
partition.  Personally I increased the [mac-yaboot] partition to around 2 Gb, 
but it might make more sense to have a separate 1.7 Gb HFS+ partition instead.  
The choice is yours.

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7) Step: Install Linux PPC 2k.  Start by booting from the CD ROM (restart and 
hold down the 'C' key until the screen goes black).  The CD ROM boots into the 
installer.  Just follow the instructions.

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8) Step: Configure the [mac-yaboot] partition by copying the System Folder from 
the Linux PPC CD to it.  You may have to open and close the System Folder on the 
[mac-yaboot] partition to "bless" it.  (You should see the Mac OS face on the 
folder if it's blessed).  Copy the kernel to it (the vmlinux... file).

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9) Step: Make sure the later kernel is on the [mac-yaboot] partition as 
described in items 2, 3 and 4 above.

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10) Step: Edit the yaboot.conf file.  To edit it you need to use an editor that 
ignores the file's associated type (since it's not text) such as Word or Alpha 
or something.  Alternatively you can use MacLink Plus, ResEdit, a Contextual 
Menu shareware thingie, etc. to change the type to TEXT and then use SimpleText 
or whatever.

Make it look like this, making sure to replace [mac-xxx] with the appropriate 
partition # and [kernel] with the kernel name (e.g. vmlinux-2.2.15pre14-ben1):

device=hd:
timeout=30
default=linux

image=hd:[mac-yaboot],[kernel]
    label=linux
    root=/dev/hda[linux-root]
    novideo

image=... whatever other boot configurations appear here are all optional.
      Just make sure they DON'T say "label=linux".  FYI, I have not discovered
      a configuration that lets you boot into Mac OS from yaboot (if anyone
      knows of one please let me know).

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11) Step: Booting into linux.

******** IMPORTANT *********
To get back to the Mac OS after this step you have 2 choices:
  a) Reset PRAM (do a restart from within linux and before you hear the boot 
chimes press and hold COMMAND-OPTION-P-R until you hear a SECOND boot chime) or
  b) Boot from another, MacOS bootable CD (other than the Linux PPC 2000 CD), 
such as the one that came with your computer and run Startup Disk control panel 
to set the boot partition back to your MacOS partition.  
******** IMPORTANT *********

To boot into linux:
Run the Startup Disk control panel, and select the [mac-yaboot] partition and 
restart your computer.  Enjoy.

After installation LinixPPC 2000 on my iBook se, so it is discribed in
"Details for Installing LinuxPPC 2000 on an iBook SE", I edited the yaboot.conf file

init-message = "\nWelcome to LinuxPPC!\nHit <TAB> for boot options.\n\n"
device = hd:
timeout = 50
default = linux

image = hd:11,vmlinux-2.2.15pre14
label = linux
root = /dev/hda12
novideo

and Linux is running on my iBook.
The problems booting macos9.04 or linux is very simple.

My Macos partition is /dev/hda8 
my Linux partition is /dev/hda12
my "/boot" partition is /dev/hda11

I select in the startup Disk control panel the /boot partition  for startdisk.
Now the Mac always boots linux.

But when I hit the D-key during booting, macos boots.

I found the trick with the "D-key" in a german MAC magazine ( MAC-UP or MAC-Welt)