Booting LinuxPPC was revolutionized in 1998 when Benjamin
Herrenschmidt released a utility called BootX, which gave PowerMac
owners easy dual-boot capability. The BootX utility runs in the Mac
OS as an application and comes with an extension that runs at system
startup. Prior to BootX, the only way to boot PowerMacs was to edit
their Open Firmware settings, which was a tricky proposition, at
best. BootX also provides basic video support for machines that don't
have video drivers.
With the BootX system, the Linux kernel is stored on the Macintosh
hard disk. When the user gives the command to boot into Linux, BootX
issues shutdown commands to the Mac OS. Just when the Mac is about to
restart, the Mac OS is kicked out of the computer's RAM, and Linux
begins to boot.
D.3.2. Partitioning the Hard Disk
Chapter 2, "Preparing to
Install Linux", discusses the reasons for
partitioning and general concepts behind it, whileSection 3.1.2, "Drives and Partitions Under Linux"" in Chapter 3, "Installation
and Initial
Configuration", explains the names and
sizes typically used for Linux partitions. Read those sections for
background; here I discuss information specific to LinuxPPC.
A full installation of LinuxPPC takes up about 650 MB. You'll want to
have more available for adding files and software. For a robust
installation, we recommend devoting at least one gigabyte
partition. Give it more if you can spare the disk space. It is
possible to pare down the installation to fit on a 100 MB ZIP disk,
but there's not much you can fit on there.
Before partitioning a disk, make a complete backup of
the disk. Once you partition the hard disk, all of the data on the
disk will be destroyed, and it will not be possible to recover it
after it has been partitioned.
If you only have one hard disk, back up the whole disk! After you've
backed up your data, boot the computer from the Mac OS CD-ROM that
came with the machine, and use Apple's Drive Setup utility to format
and partition the hard disk into two HFS partitions. Then install the
Mac OS on the first partition, reboot into the Mac OS, restore your
data, and resume the partitioning and installation
process.
In this sample installation, we will use a 4 GB hard drive
that has been split into two partitions of 2 GB each. The
first will become an Apple HFS partition and will need to be
installed on that partition. The second will be further partitioned
into a pair of Linux partitions.
To partition the hard disk, you'll need the Mac OS version
of pdisk, the disk partition utility.
This is provided by the Red Hat installer under the name
fdisk and can also be grabbed from ftp://ftp.linuxppc.org /pub/linuxppc/linuxppc-R4/RedHat/tools/pdisk.hqx.
(Please use an FTP mirror site to lighten the load on the LinuxPPC
system, especially if you're not in the United States. The mirror
list is at http:// www.linuxppc.org /mirrors.shtml.)
Unlike most Mac OS programs, pdisk is entirely
text-based. It's also a very literal program, in that it will do
exactly what you tell it to do. It won't delete your hard disk--unless you tell it to. To
make it harder to accidentally wipe
everything out, pdisk has a few safeguards built
in:
It won't save any changes unless you specifically tell it to do so.
If you quit the program (In the File menu, choose Quit), it will not save the changes
you've made to your hard disk. You have to tell it to save the
changes with the w (write) command.
The pdisk commands are shown in Table D-1.
Table D-1. pdisk Partitioning Commands
| Command |
Purpose |
| e |
Edits a device's map. A "device" is a hard disk. |
| h |
Prints the available commands. |
| l |
Lists a device's partition map. |
| L |
Lists all devices' maps. |
| q |
Quits the program. |
| v |
Prints the version number and release date. |
When you use pdisk, you're actually editing your
hard disk's partition map. The partition map is a scary sounding name
for a file that contains a list of all the partitions on your hard
disk. The partition map is stored on a partition all
its own.
When you're in the Mac OS, you see only one partition, which you think
of as your hard disk. The other four partitions are invisible, and
you don't have any reason to directly interact with them. (Unless
you've decided to go and install Linux.) The first partition holds
the partition map. The next three are device drivers, pieces of
software that tells the Mac how to use the hard disk and where to
look for the Mac OS partition. Your Mac OS software and the OS are
stored on the fifth partition, which is an Apple HFS or HFS Plus
partition.
NOTE
As of this writing, LinuxPPC cannot read HFS Extended (also known as
HFS Plus) disks, including hard disks. Research is under way to get
HFS Plus support working, but there isn't a date set for when we'll
have HFS Plus compatibility. Check on http://www.linuxppc.org for an announcement.
When you start up pdisk, it presents you with a text prompt:
Top level command (? for help):
Now what? Type
L and press Return. The
system will print out a list of every SCSI and IDE device attached to
your computer, including hard disks, CD-ROM drive, ZIP drive, and so on:
Top level command (? for help): L
pdisk: can't open file '/dev/sda' (No such device)
pdisk: can't open file '/dev/sdb' (No such device)
pdisk: can't open file '/dev/sdc' (No such device)
pdisk: can't open file '/dev/sde' (No such device)
pdisk: can't open file '/dev/sdf' (No such device)
pdisk: can't open file '/dev/sdg' (No such device)
Partition map (with 512 byte blocks) on '/dev/hda'
#: type name length base ( size )
1: Apple_partition_map Apple 63 @ 1
2: Apple_Driver43*Macintosh 54 @ 64
3: Apple_Driver43*Macintosh 74 @ 118
4: Apple_Driver_ATA*Macintosh 54 @ 192
5: Apple_Driver_ATA*Macintosh 74 @ 246
6: Apple_Patches Patch Partition 512 @ 320
7: Apple_HFS untitled 4194304 @ 832 ( 2.0G)
8: Apple_HFS untitled 4256944 @ 4195136 ( 2.0G)
If you don't have any SCSI devices on your machine, you'll see a bunch of error messages go whizzing by that say things similar to:
pdisk: can't open file '/dev/sda' (No such device)
pdisk: can't open file '/dev/sdb' (No such device)
The
can't open file messages are
pdisk's cryptic
way of reporting that it didn't find any device attached to your
computer at that address. Instead of referring to a device as
CD-ROM
Drive at SCSI ID 4 or
ATAPI HD 1,
pdisk uses
Linux's device name format. To Linux, everything is a device. Your
modem, your hard disk, the floppy drive, even the RAM are considered devices.
The name of a hard disk depends on whether it's an IDE or SCSI hard disk. IDE disks are
referred to as /dev/hdx,
and SCSI disks are /dev/sdx.
The variable x is one of the letters
a, b, c,
d, e, f, or
g. The letter on the end of the name is how Linux
distinguishes between drives.
Did you notice that IDE drives are hd and SCSI drives are sd?
Those letters just denote which bus the devices are on. The letter
after hd or sd is what you really need to pay attention to. If
your computer has one IDE hard disk in it, it will be listed as
/dev/hda. You also will get an error on
/dev/hdb, which is your CD-ROM drive. Don't
worry about it, though. (Trust me!)
If you have SCSI drives in your computer, pdisk
will first display their names with "fake" SCSI names in the format
/dev/scsibus.scsi_id, such as /dev/sdc1.5.
Fortunately, it also lists their device name in proper
/dev/sdletter format.
Linux refers to SCSI devices with the
/dev/sdletter scheme, so
use that format when working with the device.
If you have an Ultra/Wide SCSI card by Adaptec or Apple, and you're
planning on installing Linux on the hard disk attached to the card, prepare
to be a little confused. Linux might say that your hard disk is in a
different place than pdisk says it's in. This is
because when Linux boots, it looks at the names of the devices
attached to it. The Adaptec and Apple Ultra-Wide SCSI cards show up
on the letter A. The Mac's SCSI controller is
called the MESH chip, which is alphabetically after "Adaptec."
A hard disk on an Adaptec card will be at
/dev/sda. Devices on the regular internal SCSI
bus will follow at /dev/sdb and
/dev/sdc. If your machine has only one device on
the SCSI card, you're in the clear. If you have other devices
attached to it, the naming game can get a little hairy.
And now, we partition:
Choose the partition you're going to edit. In
pdisk, type the letter e:
Top level command (? for help): e
Name of device: /dev/hda
Edit /dev/hda -
Command (? for help):
Delete the second HFS partition. You have to delete the partition in order
to create free space, which you will use to make Linux partitions. Looking at the partition map, the seventh partition is the HFS
partition, which will be erased. To delete a partition, type the letter
d followed by the number of the partition you wish
to delete:
Command (? for help): d8
Command (? for help): p
Typing p again will display the partition map. The Apple HFS
partition has turned into free space, which you can use to make new partitions:
7: Apple_HFS untitled 4194304 @ 832 ( 2.0G)
8: Apple_Free Extra 4256944 @ 4195136 ( 2.0G)
Create the swap partition:
Command (? for help): c "c" is the command to make a new partition.
First block: 8p "8p": Use the first block of the free space partition,
which is the eighth partition.
Length in blocks: 30m Make it 30MB. k = kb, m = mb, g = gb
Name of partition: swap The partition will be called swap.
Command (? for help):
There! You've created your swap partition. Print out the partition map again. Examine the eighth and ninth partitions:
8: Apple_UNIX_SVR2 swap 61440 @ 4195136 ( 30.0M)
9: Apple_Free Extra 4195504 @ 4256576 ( 2.0G)
The free space is now the ninth partition, and the new swap partition
is at
/dev/hda7. Next, make the root partition. Once you make root, you will be done partitioning.
When creating the root partition, instead of typing the length in
megabytes, use the free-space partition's length in blocks. In this
example, the Apple_Free partition is 4,195,504 blocks long, which is
roughly 2 GB. By typing the partition's exact length in blocks, you
will use up all the available disk space and not have wasted space left over after partitioning:
Command (? for help): c
First block: 9p
Length in blocks: 4195504
Name of partition: root
Command (? for help): p
Partition map (with 512 byte blocks) on '/dev/hda'
#: type name length base ( size )
1: Apple_partition_map Apple 63 @ 1
2: Apple_Driver43*Macintosh 54 @ 64
3: Apple_Driver43*Macintosh 74 @ 118
4: Apple_Driver_ATA*Macintosh 54 @ 192
5: Apple_Driver_ATA*Macintosh 74 @ 246
6: Apple_Patches Patch Partition 512 @ 320
7: Apple_HFS untitled 4194304 @ 832 ( 2.0G)
8: Apple_UNIX_SVR2 swap 61440 @ 4195136 ( 30.0M)
9: Apple_UNIX_SVR2 root 4195504 @ 4256576 ( 2.0G)
In this example, partition /dev/hda9 will become your root
device. Write down which partition is your root device. You will
need to know that later. If you have a SCSI hard disk, it would be
/dev/sda7. Also note that if you are planning on
installing Linux on a drive other than your startup disk, you don't
have to have the Apple_HFS partition on the disk. You can devote the
entire drive to Linux.
When you're done partitioning, type w:
Command (? for help): w
Writing the partition map will permanently save changes.
Save changes? (y/N): y
pdisk will come back to the
Top level
command prompt. At this point, the changes to your hard
disk will have been saved. Type
q to quit
pdisk.
Tips for partitioning include the following:
If you make a mistake, it's not fatal. You can quit
pdisk at any time without saving changes.
Changes are not final until you tell pdisk to write
the new partition map with the w command.
