macppc system bootstrapping procedures
When powered on, after a panic, or if the system is rebooted via
, the Open Firmware
will proceed to its initialization, and will boot an operating system if the
variable is set to
“true”, or will wait for interactive commands otherwise.
The Apple Open Firmware will normally load the kernel from the device and
filename as instructed by the boot-device
variables. If the
variable is empty, the
bootloader will look for a kernel named
, unless a different filename has been
specified in the boot command. To reset this variable to its default, empty,
value, type the following at the Open Firmware prompt:
bootstrap program is named
“ofwboot”. It can be installed either in a HFS partition or in a
MSDOS partition on the disk. If MBR partitioning is chosen for the disk, the
bootstrap program will be installed automatically during the
installation procedure. For HFS shared disks,
file must be installed manually. The
ofwboot program can be loaded from any Open Firmware recognized disk or
If invoked manually without parameters, or if the specified kernel could not be
loaded, the OpenBSD
bootloader will let the user enter
a boot device, kernel filename and boot options.
If the special line exit
is entered, the bootloader
will attempt to restart the machine.
The file specification used is of the form:
where: “promdev” is an optional Open Firmware device name (such as
“hd” or “ide”) and “partition” is an
optional disk partition number. Normal line editing characters can be used
when typing the file specification.
The following options are recognized:
- Prompt for the root filesystem and swap devices after the
devices have been configured.
- Enter the “User Kernel Config” mode upon
- Enter the debugger,
ddb(4), as soon as the kernel
console has been initialized.
- Boot the system single-user. The system will be booted
multi-user unless this option is specified.
In case of system crashes, the kernel will usually enter the kernel debugger,
, unless it is not present in
the kernel, or it is disabled via the
sysctl. Upon leaving ddb, or if ddb
was not entered, the kernel will halt the system if it was still in device
configuration phase, or attempt a dump to the configured dump device, if
possible. The crash dump will then be recovered by
during the next
multi-user boot cycle. It is also possible to force other behaviours from ddb.
The prom can only be accessed during system reset, or at power-up. To enter Open
Firmware, press and hold “Cntrl” “Cmd”
“o” “f” as the machine resets until it enters the
Open Firmware debugger.
On an Xserve using serial console the System Identifier button is used to enter
Open Firmware instead of the keyboard. To enter Open Firmware, hold down the
System Identifier button while pressing the Power button. When the upper LED
bank begins lighting up in sequence, repeatedly press the System Identifier
button until the seventh LED from the right is highlighted in the lower bank.
Now hold the System Identifier button for two seconds, until all the top row
LEDs light up.
- default system kernel
- standalone installation kernel, suitable for disaster
- system bootstrap (usually installed on a stand-alone FAT
partition or an Apple HFS partition, to be readable by Open Firmware)