Your system's first boot on its own power is what electrical engineers call the “smoke test”.
If you are booting directly into Debian, and the system doesn't start
up, either use your original installation boot media, or insert the
custom boot floppy if you have one, and reset your system. This way,
you will probably need to add some boot arguments like
root=, where
rootroot is your root partition, such as
/dev/sda1.
If the machine fails to boot after completing the installation, and
stops with a boot: prompt, try typing
Linux followed by Enter. (The default boot
configuration in quik.conf is labeled Linux). The
labels defined in quik.conf will be displayed if
you press the Tab key at the boot:
prompt. You can also try booting back into the installer, and editing
the /target/etc/quik.conf placed there by the
step. Clues
for dealing with quik are available at
http://penguinppc.org/projects/quik/.
To boot back into MacOS without resetting the nvram, type
bye at the OpenFirmware prompt (assuming MacOS
has not been removed from the machine). To obtain an OpenFirmware
prompt, hold down the command-option-o-f keys while cold booting the machine. If you need to reset
the OpenFirmware nvram changes to the MacOS default in order to boot
back to MacOS, hold down the command-option-p-r keys while cold booting the machine.
If you use BootX to boot into the installed system,
just select your desired kernel in the Linux
Kernels folder, un-choose the ramdisk option, and add
a root device corresponding to your installation;
e.g. /dev/hda8.
On G4 machines and iBooks, you can hold down the option key and get a graphical screen with a button for each bootable OS, Debian GNU/Linux will be a button with a small penguin icon.
If you kept MacOS and at some point it changes the OpenFirmware
boot-device variable you should reset OpenFirmware to
its default configuration. To do this hold down the command-option-p-r keys while cold booting the machine.
The labels defined in yaboot.conf will be
displayed if you press the Tab key at the
boot: prompt.
Resetting OpenFirmware on G3 or G4 hardware will cause it to boot
Debian GNU/Linux by default (if you correctly partitioned and placed the
Apple_Bootstrap partition first). If you have Debian GNU/Linux on a SCSI disk
and MacOS on an IDE disk this may not work and you will have to enter
OpenFirmware and set the boot-device variable,
ybin normally does this automatically.
After you boot Debian GNU/Linux for the first time you can add any additional
options you desire (such as dual boot options) to
/etc/yaboot.conf and run ybin
to update your boot partition with the changed configuration. Please
read the yaboot HOWTO
for more information.