Your system's first boot on its own power is what electrical engineers call the “smoke test”.
If the system fails to start up correctly, don't panic. If the installation was successful, chances are good that there is only a relatively minor problem that is preventing the system from booting Ubuntu. In most cases such problems can be fixed without having to repeat the installation. One available option to fix boot problems is to use the installer's built-in rescue mode (see the section called “Recovering a Broken System”).
On G4 machines and iBooks, you can hold down the option key and get a graphical screen with a button for each bootable OS, Ubuntu 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
Ubuntu by default (if you correctly partitioned and placed the
Apple_Bootstrap partition first). If you have Ubuntu 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 Ubuntu 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.
