For preparing 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
will probably have to turn off its write protection switch.
Note that the USB stick should be at least 8 MB in size. If you follow Section 4.3.2, “Copying the files — the flexible way” and want to include an Ubuntu ISO image on the stick, you will need enough space for the ISO as well.
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. 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
Of course this will destroy anything already on the device, so take care that you use the correct device name for your USB stick.
If you like more flexibility or just want to know what's going on, you should use the following method to put the files on your stick.
Most USB sticks do not come pre-configured in such a way that Open
Firmware can boot from them, so you will need to repartition the stick.
On Mac systems, run mac-fdisk /dev/sda,
initialise a new partition map using the i
command, and create a new partition of type Apple_Bootstrap using the
C command. (Note that the first "partition" will
always be the partition map itself.) Then type
$ hformat /dev/sda2
Take care that you use the correct device name for your USB stick. The
hformat command is contained in the
hfsutils Ubuntu package.
In order to start the kernel after booting from the USB stick, we will put a boot loader on the stick. The yaboot boot loader can be installed on an HFS filesystem and can be reconfigured by just editing a text file. Any operating system which supports the HFS file system can be used to make changes to the configuration of the boot loader.
The normal ybin tool that comes with
yaboot does not yet understand USB storage devices,
so you will have to install yaboot by hand using the
hfsutils tools. Type
$ hmount /dev/sda2 $ hcopy -r /usr/lib/yaboot/yaboot : $ hattrib -c UNIX -t tbxi :yaboot $ hattrib -b : $ humount
Again, take care that you use the correct device name. The partition must not be otherwise mounted during this procedure. This procedure writes the boot loader to the partition, and uses the HFS utilities to mark it in such a way that Open Firmware will boot it. Having done this, the rest of the USB stick may be prepared using the normal Unix utilities.
Mount the partition (mount /dev/sda2 /mnt) and
copy the following files from the Ubuntu archives to the stick:
vmlinux (kernel binary)
initrd.gz (initial ramdisk image)
yaboot.conf (yaboot configuration file)
boot.msg (optional boot message)
Optional kernel modules
The yaboot.conf configuration file should
contain the following lines:
default=install
root=/dev/ram
message=/boot.msg
image=/vmlinux
label=install
initrd=/initrd.gz
initrd-size=10000
append="--"
read-only
Please note that the initrd-size parameter
may need to be increased, depending on the image you are booting.
If you are using the hd-media image, you should
now put any Ubuntu ISO image onto your stick (if it fits).
The file name of such an
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.