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Booting from open firmware

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Booting from Open Firmware

There are different possibilities to boot a PPC based NewWorld Apple computer. One can boot the traditional CD-ROM, a hard disk, a USB stick or even a Linux distribution which is served over the internet. In this article these options are going to be dealt with. M">1. Booting CD-ROM k">2. Booting from a hard disk B">3. Booting from a USB memory stick P">4. Booting via a network with TFTP s">Boot parameters for older PPC machines


1. Booting CD-ROM
The easiest way for people to install a Linux distribution, is to use a CD-ROM. In most cases a Mac can be booted off a CD-ROM by keeping the "c" key pressed during boot. The Mac should then automatically boot from the CD, provided that the CD-ROM is a PPC compatible one. There are Macs however, due to problems with firmware, are not able to do this. One could then also try to boot with the "Option" key hold during boot. The "Option" key is the key between the CTRL and Apple (Command) key. With this key, one should see the possible bootable devices on the Mac. If both these methods fail, one can always fall back on the Open Firmware boot option. To enter Open Firmware, one has to hold "Option"+"Command"+"o"+"f". You will be welcomed with a open firmware prompt. To then boot a CD-ROM, issue the following code:

boot cd:,\\:tbxi


2. Booting from a hard disk

NewWorld PowerMacs support booting from a network or an ISO9660 CD-ROM, as well as loading ELF binaries directly from the hard disk. These machines will boot Linux directly via yaboot, which supports loading a kernel and RAMdisk directly from an ext2 partition, as well as dual-booting with MacOS. Hard disk booting of the installer is particularly appropriate for newer machines without floppy drives. BootX is not supported and must not be used on NewWorld PowerMacs.

Copy (not move) the following four files which you downloaded earlier from the Linux archives, onto the root level of your hard drive (this can be accomplished by option-dragging each file to the hard drive icon).

  • vmlinux
  • initrd.gz
  • yaboot
  • yaboot.conf


Make a note of the partition number of the MacOS partition where you place these files. If you have the MacOS pdisk program, you can use the L command to check for the partition number. You will need this partition number for the command you type at the Open Firmware prompt when you boot the installer. To boot the installer, restart the computer, and immediately (during the chime) hold down the Option, Command (cloverleaf/Apple), o, and f keys all together. After a few seconds you will be presented with the Open Firmware prompt. At the prompt, type:

boot hd:x,yaboot

replacing x with the partition number of the HFS partition where the kernel and yaboot files were placed, followed by a Enter. On some machines, you may need to use ide0: instead of hd:. In a few more seconds you will see a yaboot prompt:


At yaboot's boot: prompt, type either install or install video=ofonly followed by a Enter. The video=ofonly argument is for maximum compatibility; you can try it if install doesn't work.


3. Booting from a USB memory stick
Currently, NewWorld PowerMac systems are known to support USB booting. To prepare the USB stick, you will need a system where GNU/Linux is already running and where USB is supported. You should ensure that the usb-storage kernel module is loaded (modprobe usb-storage) and try to find out which SCSI device the USB stick has been mapped to (in this example /dev/sda is used). To write to your stick, you may have to turn off its write protection switch.

Note that the USB stick should be at least 8 MB in size.

Copying the files - the flexible way

Copying the files - the easy way:

If you're lucky, there is an all-in-one file netboot/boot.img.gz which contains all the installer files (including the kernel) as well as yaboot and its configuration file in the iso or on the CD-ROM. Create a partition of type "Apple_Bootstrap" on your USB stick using mac-fdisk's C command and extract the image directly to that:

zcat boot.img.gz > /dev/sda2

Using this method will destroy anything already on the device. Make sure that you use the correct device name for your USB stick.

Adding an ISO image

The installer will look for a Linux ISO image on the stick as its source for additional data needed for the installation. So your next step is to copy the Linux ISO image onto your stick (be sure to select one that fits). The file name of the image must end in .iso.

If you want to install over the network, without using an ISO image, you will of course skip the previous step. Moreover you will have to use the initial ramdisk from the netboot directory instead of the one from hd-media, because hd-media/initrd.gz does not have network support.

When you are done, unmount the USB memory stick (umount /mnt) and activate its write protection switch.

Booting the USB stick

To boot a Macintosh system from a USB stick, you will need to use the Open Firmware prompt, since Open Firmware does not search USB storage devices by default. To get to the prompt, hold down Command+Option+o+f all together while booting.

You will need to work out where the USB storage device appears in the device tree, since at the moment ofpath cannot work that out automatically. Type dev / ls and devalias at the Open Firmware prompt to get a list of all known devices and device aliases. On the author's system with various types of USB stick, paths such as usb0/disk, usb0/hub/disk, /pci@f2000000/usb@1b,1/disk@1, and /pci@f2000000/usb@1b,1/hub@1/disk@1 work.

boot usb0/disk:2,\\:tbxi

The 2 matches the Apple_HFS or Apple_Bootstrap partition onto which you copied the boot image earlier, and the ,\\:tbxi part instructs Open Firmware to boot from the file with an HFS file type of "tbxi" (i.e. yaboot) in the directory previously blessed with hattrib -b.
The system should now boot up, and you should be presented with the boot: prompt. Here you can enter optional boot arguments, or just hit Enter.


4. Booting via a network with TFTP
Booting from the network requires that you have a network connection and a TFTP network boot server (DHCP, RARP, or BOOTP).

The installation method to support network booting is described in the section called “Preparing Files for TFTP Net Booting”.

Currently, PReP and New World PowerMac systems support netbooting.

On machines with Open Firmware, such as NewWorld Power Macs, enter open firmware (see above) and use the command:

boot enet:0

PReP and CHRP boxes may have different ways of addressing the network. On a PReP machine, you should try 


boot server_ipaddr,file,client_ipaddr


 You can also have a look at n">this page for more information.


PowerPC Boot Parameters

Many older Apple monitors used a 640x480 67Hz mode. If your video appears skewed on an older Apple monitor, try appending the boot argument video=atyfb:vmode:6 , which will select that mode for most Mach64 and Rage video hardware. For Rage 128 hardware, this changes to video=aty128fb:vmode:6 .

To read more about Open Firmware follow 0">this and e">this link.

Garyz Satterfield
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Joined: 1 month ago
Posts: 1

Just a note about Live USB on my Dual 2.0 Ghz G5...i managed to get the live image copied over to a USB thumb drive, and finally figured out the Open Firmware commands to boot it: boot usb:\boot\grub.elf. This begins to boot, but almost immediately shows me the "Prohibitory Symbol", causing me to have to reboot.

So this tells me there is something wrong with the live image I copied to the USB drive. I even redid my dd copy of the Live Image, and even tried it on another Linux box. Same results.

Anyone else had this issue with the Live Image? Or am I just dealing with a cockeyed machine?

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I packed all my computers....