The BootX utility frees you from any dealing with OF, and it gives you easy dual-boot ability. You can choose to boot the Mac OS or Linux on startup, or switch to Linux from the Mac OS. It's that easy.

Go to: http://www.linuxppc.org/bootx.html

That page has the info for getting and using BootX.

The documentation that follows this entry is still useful if, and only if, you want to use the "old" installation method.
jhaas@linuxppc.org

To anyone who is going to give all this a go on a G3 with its shipped IDE drive, I suggest that:

Once you get your installation done, reboot with cmd-opt-p-r to reset to a nice clean out of the box OF. This means you will lose some MacOS settings, but what the hell...

Boot into MacOS and do the multibooter bit to set the values as follows:

boot-device: ide/disk@0:X
boot-file: /boot/vmlinux root=/dev/hdaX

where X is your IDE root partition

and set auto-boot to off - this way you may have an opportunity to get back into macos if anything goes seriously wrong.

Restart the computer.

Type "boot" at the OF screen, until you get CLAIM FAILED.
Type "bye" and proceed to boot MacOS
MacOS will gives you the blinking question mark.
Restart with cmd-opt-power to get OF
Type "boot" again, and Linux boots off the IDE drive with no problems.

Still with me? now go over to ftp.linuxppc.org/users/harry and get g3fix.tgz

"gunzip" then "tar -xvf" it. Follow the instructions in the resulting README file.

It works from there on in, and you get a nice OF boot selector menu to boot (pun intended...)

daniel.figucio@cbr.clw.csiro.au

The above description from daniel.figucio@cbr.clw.csiro.au matches my experience
with installing LinuxPPC 4 on my G3 233 desktop internal IDE, however, in 
reading the instructions from various places they said to download a lot of 
files it turned out were already on the Release 4 CD, so I have summarized my 
experience with that distribution here:

Formatted hard disk using Drive Setup with partitions suggested in Linux install
userguide

http://www.linuxppc.org/userguide/part.html

Then I used pdisk for MacOS from the CD macosutils directory to convert the
partitions to Apple UNIX format. This is easier than doing it during the install
as you can cut and paste the first block and length when you run it in MacOS.

The next step is to format a floppy and put the G3 installer (g3installer.coff)
on it, this file is on the CD in the RedHat:images: directory.

Next you want to tell Open Firmware to boot using that file on the floppy, so
you actually have to download a file, Multibooter 

ftp://ftp.apple.com/devworld/Rhapsody/UsefulStuff/Multibooter1.0d13.sit

In Multibooter select Network Disk (Open Firmware), Advanced Options,
Boot-Device fd:g3installer.coff, OK, Save

Put your floppy in the drive, Restart, and away you go.
You may need to set your load-base to 100000, it's not clear to me whether that
is necessary or not, if so, you can read about that elsewhere.

Once the install is done and it asks about setting up Quik, say OK, because 
the distribution already has the latest 1.3 Quik that will allow hard disk 
booting.

From there on in, things proceeded as described "Once you get the installation
done..." by daniel.figucio@cbr.clw.csiro.au above, weird but it works.  I didn't
install the boot menu, found it kind of annoying, if you turn off auto-boot you
can still select MacOS or Linux by typing "bye" for MacOS and "boot" for Linux 
at the OF prompt.

All of this multibooter stuff is no longer necessary.  I had been attempting
to even run the installer on my g3/300 for over a week with this and I never 
got anything but CLAIM FAILED. 
        Bootx is here.  I downloaded the beta from mirror.aarnet.au.edu and that was
it.  I installed it as it said in about 30 seconds, and it worked the first time.
Once the system was installed I put: root=/dev/sda4 noinitrd  
        It boots up with a nice menu at startup where you choose either MacOs or 
Linux.  Otherwise you can just open the app once in MacOs and it will boot right
there if you select it.  No messing with rom variables or anything, and finally
NO CLAIM FAILED ERROR.

Jeff Rose

I can't emphasise enough the wonder that is BootX. As Jeff says,
download it and use it when you're installing linux on a G3 (mine's
a 300 and it worked where all else failed, I think it's a rev 3).

Get BootX, the ramdisk, and the vmlinux files, stick em where it says,
and check the "Use Ram disk" box, and away you go, it really
is that simple.

To Benjamin Herrenschmidt, the author of BootX, much kudos.

The BootX page is at http://linuxppc.org/bootx.html
You'll find the app on the ftp site.

Enjoy

Steve