en/handbook/hb-install-ppc-disk.xml

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<sections>

<version>8.0</version>
<date>2007-05-07</date>

<section>
<title>Introduction to Block Devices</title>
<subsection>
<title>Block Devices</title>
<body>

<p>
We'll start by taking a good look at disk-oriented aspects of Gentoo Linux
and Linux in general, including Linux filesystems, partitions and block devices.
Then, once you're familiar with the ins and outs of disks and filesystems,
you'll be guided through the process of setting up partitions and filesystems
for your Gentoo Linux installation.
</p>

<p>
To begin, we'll introduce <e>block devices</e>. The most common block device is
the one that represents the first IDE drive in a Linux system, namely
<path>/dev/hda</path>. If you are installing onto SCSI, FireWire, USB or SATA 
drives, then your first hard drive would be <path>/dev/sda</path>.  Additional
drives are enumerated by the next letter in the alphabet.  As an example, the
third IDE disk could be found at <path>/dev/hdc</path>.
</p>

<p>
The block devices above represent an abstract interface to the disk. User
programs can use these block devices to interact with the disk without worrying
about whether the drives are IDE, SCSI or something else. The program can
simply address the storage on the disk as a bunch of contiguous,
randomly-accessible 512-byte blocks.
</p>

</body>
</subsection>
<subsection>
<title>Partitions</title>
<body>

<p>
Although it is theoretically possible to use a full disk to house your Linux
system, this is almost never done in practice. Instead, full disk block devices
are split up in smaller, more manageable block devices. On most systems,
these are called <e>partitions</e>.
</p>

</body>
</subsection>
</section>
<section>
<title>Designing a Partitioning Scheme</title>
<subsection>
<title>Default Partitioning Scheme</title>
<body>

<p>
If you are not interested in drawing up a partitioning scheme for your system,
you can use the partitioning scheme we use throughout this book.  Choose the
filesystem layout that best matches the type of PowerPC system you are 
installing on.
</p>

</body>
</subsection>
<subsection>
<title>Apple New World</title>
<body>

<p>
Apple New World machines are fairly straightforward to configure.  The first
partition is always an <e>Apple Partition Map</e>.  This partition keeps track
of the layout of the disk.  You cannot remove this partition.  The next
partition should always be a bootstrap partition.  This partition contains a
small (800k) HFS filesystem that holds a copy of the bootloader Yaboot and its
configuration file.  This partition is <e>not</e> the same as a 
<path>/boot</path> partition as found on other architectures.  After the boot
partition, the usual Linux filesystems are placed, according to the scheme
below.  The swap partition is a temporary storage place for when your system
runs out of physical memory.  The root partition will contain the filesystem
that Gentoo is installed on.  If you wish to dual boot, the OSX partition 
can go anywhere after the bootstrap partition to insure that yaboot starts 
first.
</p>

<note>
There may be "Disk Driver" partitions on your disk such as
<path>Apple_Driver63</path>, <path>Apple_Driver_ATA</path>,
<path>Apple_FWDriver</path>, <path>Apple_Driver_IOKit</path>, and
<path>Apple_Patches</path>.  These are used to boot MacOS, so if you have no
need for this, you can remove them by initializing the disk with mac-fdisk's
<c>i</c> option.  This will completely erase the disk!  If you are in doubt,
just let them be.
</note>

<note>
If you partitioned this disk with Apple's Disk Utility, there may be
128Mb spaces between partitions which Apple reserves for "future use".  You
can safely remove these.
</note>

<table>
<tr>
  <th>Partition</th>
  <th>Size</th>
  <th>Filesystem</th>
  <th>Description</th>
</tr>
<tr>
  <ti><path>/dev/hda1</path></ti>
  <ti>32k</ti>
  <ti>None</ti>
  <ti>Apple Partition Map</ti>
</tr>
<tr>
  <ti><path>/dev/hda2</path></ti>
  <ti>800k</ti>
  <ti>HFS</ti>
  <ti>Apple Bootstrap</ti>
</tr>
<tr>
  <ti><path>/dev/hda3</path></ti>
  <ti>512Mb</ti>
  <ti>Swap</ti>
  <ti>Linux Swap</ti>
</tr>
<tr>
  <ti><path>/dev/hda4</path></ti>
  <ti>Rest of Disk</ti>
  <ti>ext3, reiserfs, xfs</ti>
  <ti>Linux Root</ti>
</tr>
</table>

</body>
</subsection>
<subsection>
<title>Apple Old World</title>
<body>

<p>
Apple Old World machines are a bit more complicated to configure. The first
partition is always an <e>Apple Partition Map</e>.  This partition keeps track
of the layout of the disk.  You cannot remove this partition.  If you are using
BootX, the configuration below assumes that MacOS is installed on a seperate
disk.  If this is not the case, there will be additional partitions for "Apple
Disk Drivers" such as <path>Apple_Driver63, Apple_Driver_ATA, Apple_FWDriver,
Apple_Driver_IOKit, Apple_Patches</path> and the MacOS install.  If you are 
using Quik, you will need to create a boot partition to hold the kernel, unlike
other Apple boot methods. After the boot partition, the usual Linux filesystems
are placed, according to the scheme below.  The swap partition is a temporary
storage place for when your system runs out of physical memory.  The root 
partition will contain the filesystem that Gentoo is installed on.
</p>

<note>
If you are using an OldWorld machine, you will need to keep MacOS available.
The layout here assumes MacOS is installed on a separate drive.
</note>

<table>
<tr>
  <th>Partition</th>
  <th>Size</th>
  <th>Filesystem</th>
  <th>Description</th>
</tr>
<tr>
  <ti><path>/dev/hda1</path></ti>
  <ti>32k</ti>
  <ti>None</ti>
  <ti>Apple Partition Map</ti>
</tr>
<tr>
  <ti><path>/dev/hda2</path></ti>
  <ti>32Mb</ti>
  <ti>ext2</ti>
  <ti>Quik Boot Partition (quik only)</ti>
</tr>
<tr>
  <ti><path>/dev/hda3</path></ti>
  <ti>512Mb</ti>
  <ti>Swap</ti>
  <ti>Linux Swap</ti>
</tr>
<tr>
  <ti><path>/dev/hda4</path></ti>
  <ti>Rest of Disk</ti>
  <ti>ext3, reiserfs, xfs</ti>
  <ti>Linux Root</ti>
</tr>
</table>

</body>
</subsection>
<subsection>
<title>Pegasos</title>
<body>

<p>
The Pegaos partition layout is quite simple compared to the Apple layouts.
The first partition is a Boot Partition, which contains kernels to be booted,
along with an OpenFirmware script that presents a menu on boot.  After the boot
partition, the usual Linux filesystems are placed, according to the scheme
below.  The swap partition is a temporary storage place for when your system
runs out of physical memory.  The root partition will contain the filesystem
that Gentoo is installed on.  
</p>

<table>
<tr>
  <th>Partition</th>
  <th>Size</th>
  <th>Filesystem</th>
  <th>Description</th>
</tr>
<tr>
  <ti><path>/dev/hda1</path></ti>
  <ti>32Mb</ti>
  <ti>affs1 or ext2</ti>
  <ti>Boot Partition</ti>
</tr>
<tr>
  <ti><path>/dev/hda2</path></ti>
  <ti>512Mb</ti>
  <ti>Swap</ti>
  <ti>Linux Swap</ti>
</tr>
<tr>
  <ti><path>/dev/hda3</path></ti>
  <ti>Rest of Disk</ti>
  <ti>ext3, reiserfs, xfs</ti>
  <ti>Linux Root</ti>
</tr>
</table>

</body>
</subsection>
<subsection>
<title>IBM PReP (RS/6000)</title>
<body>

<p>
The Pegaos partition layout is quite simple compared to the Apple layouts.
The first partition is a Boot Partition, which contains kernels to be booted,
along with an OpenFirmware script that presents a menu on boot.  After the boot
partition, the usual Linux filesystems are placed, according to the scheme
below.  The swap partition is a temporary storage place for when your system
runs out of physical memory.  The root partition will contain the filesystem
that Gentoo is installed on.  
</p>

<table>
<tr>
  <th>Partition</th>
  <th>Size</th>
  <th>Filesystem</th>
  <th>Description</th>
</tr>
<tr>
  <ti><path>/dev/hda1</path></ti>
  <ti>800k</ti>
  <ti>None</ti>
  <ti>PReP Boot Partition (Type 0x41)</ti>
</tr>
<tr>
  <ti><path>/dev/hda2</path></ti>
  <ti>512Mb</ti>
  <ti>Swap</ti>
  <ti>Linux Swap (Type 0x82)</ti>
</tr>
<tr>
  <ti><path>/dev/hda3</path></ti>
  <ti>Rest of Disk</ti>
  <ti>ext3, reiserfs, xfs</ti>
  <ti>Linux Root (Type 0x83)</ti>
</tr>
</table>

<warn>
<c>parted</c> is able to resize partitions including HFS+. Unfortunately there
may be issues with resizing HFS+ journaled filesystems, so, for the best 
results, switch off journaling in Mac OS X before resizing. Remember that any
resizing operation is dangerous, so attempt at your own risk! Be sure to always
have a backup of your data before resizing!
</warn>

<p>
If you are interested in knowing how big a partition should be, or even how many
partitions you need, read on. Otherwise continue now with 
<uri link="#mac-fdisk"> Default: Using mac-fdisk (Apple) to Partition your Disk
</uri> or <uri link="#parted">Alternative: Using parted (IBM/Pegasos) to 
Partition your Disk</uri>.
</p>

</body>
</subsection>
<subsection>
<title>How Many and How Big?</title>
<body>

<p>
The number of partitions is highly dependent on your environment. For instance,
if you have lots of users, you will most likely want to have your
<path>/home</path> separate as it increases security and makes backups easier.
If you are installing Gentoo to perform as a mailserver, your <path>/var</path>
should be separate as all received mail is stored in <path>/var</path>. A good
choice of filesystem will then maximise your performance. Game servers should
have a separate <path>/opt</path> as most game servers are installed there. The
reason is similar for <path>/home</path>: security and backups. Whatever layout
you chose, you will definitely want to keep <path>/usr</path> large: not only 
will it contain the majority of applications, the Portage tree alone takes 
more than 500Mb excluding the various sources that are stored in it.
</p>

<p>
As you can see, it very much depends on what you want to achieve. Separate
partitions or volumes have the following advantages:
</p>

<ul>
<li>
  You can choose the best performing filesystem for each partition or volume
</li>
<li>
  Your entire system cannot run out of free space if one defunct tool is
  continuously writing files to a partition or volume
</li>
<li>
  If necessary, file system checks are reduced in time, as multiple checks can
  be done in parallel (although this advantage is more with multiple disks than
  it is with multiple partitions)
</li>
<li>
  Security can be enhanced by mounting some partitions or volumes read-only,
  nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
</li>
</ul>

<p>
However, multiple partitions have one big disadvantage: if not configured
properly, you might result in having a system with lots of free space on one
partition and none on another. There is also a 15-partition limit for SCSI and
SATA.
</p>

</body>
</subsection>
</section>
<section id="mac-fdisk">
<title>Default: Using mac-fdisk (Apple) Partition your Disk</title>
<body>

<p>
At this point, create your partitions using <c>mac-fdisk</c>:
</p>

<pre caption="Starting mac-fdisk">
# <i>mac-fdisk /dev/hda</i>
</pre>

<p>
If you used Apple's Disk Utility to leave space for Linux, first delete the
partitions you have created previously to make room for your new install.  Use
<c>d</c> in <c>mac-fdisk</c> to delete those partition(s).  It will ask for the
partition number to delete.  Usually the first partition on NewWorld machines
(Apple_partition_map) could not be deleted. If you would like to start with a 
clean disk, you can simply initialize the disk by pressing  <c>i</c>.  This 
will completely erase the disk, so use this with caution.
</p>

<p>
Second, create an <e>Apple_Bootstrap</e> partition by using <c>b</c>. It will
ask for what block you want to start. Enter the number of your first free
partition, followed by a <c>p</c>. For instance this is <c>2p</c>.
</p>

<note>
This partition is <e>not</e> a <path>/boot</path> partition. It is not used by
Linux at all; you don't have to place any filesystem on it and you should never
mount it. Apple users don't need an extra partition for <path>/boot</path>.
</note>

<p>
Now create a swap partition by pressing <c>c</c>. Again <c>mac-fdisk</c> will
ask for what block you want to start this partition from. As we used <c>2</c>
before to create the Apple_Bootstrap partition, you now have to enter
<c>3p</c>. When you're asked for the size, enter <c>512M</c> (or whatever size
you want -- a minimum of 512MB is recommended, but 2 times your physical memory
is the generally accepted size). When asked for a name, enter <c>swap</c>.
</p>

<p>
To create the root partition, enter <c>c</c>, followed by <c>4p</c> to select
from what block the root partition should start. When asked for the size, enter
<c>4p</c> again. <c>mac-fdisk</c> will interpret this as "Use all available
space". When asked for the name, enter <c>root</c>.
</p>

<p>
To finish up, write the partition to the disk using <c>w</c> and <c>q</c> to
quit <c>mac-fdisk</c>.
</p>

<note>
To make sure everything is ok, you should run <c>mac-fdisk -l</c> and check
whether all the partitions are there. If you don't see any of the partitions
you created, or the changes you made, you should reinitialize your partitions
by pressing "i" in mac-fdisk. Note that this will recreate the partition map
and thus remove all your partitions.
</note>

<p>
Now that your partitions are created, you can continue with 
<uri link="#filesystems">Creating Filesystems</uri>.
</p>

</body>
</section>
<section id="parted">
<title>Using parted to Partition your Disk (Pegasos and RS/6000)</title>
<body>

<p>
<c>parted</c>, the Partition Editor, can now handle HFS+ partitions used by
Mac OS and Mac OS X.  With this tool you can resize your Mac-partitions and
create space for your Linux partitions.  Nevertheless, the example below
describes partitioning for Pegasos machines only.
</p>

<p>
To begin let's fire up <c>parted</c>:
</p>

<pre caption="Starting parted">
# <i>parted /dev/hda</i>
</pre>

<p>
If the drive is unpartitioned, run <c>mklabel amiga</c> to create a new 
disklabel for the drive.
</p>

<p>
You can type <c>print</c> at any time in parted to display the current partition
table. If at any time you change your mind or made a mistake you can press
<c>Ctrl-c</c> to abort parted.
</p>

<p>
If you intend to also install MorphOS on your Pegasos create an affs1 filesystem
at the start of the drive. 32MB should be more than enough to store the MorphOS
kernel. If you have a Pegasos I or intend to use any filesystem besides ext2 or 
ext3, you will also have to store your Linux kernel on this partition (the 
Pegasos II can only boot from ext2/ext3 or affs1 partitions). To create the 
partition run <c>mkpart primary affs1 START END</c> where <c>START</c> and 
<c>END</c> should be replaced with the megabyte range (e.g. <c>0 32</c> which 
creates a 32 MB partition starting at 0MB and ending at 32MB.  If you chose to
create an ext2 or ext3 partition instead, substitute ext2 or ext3 for affs1 in
the mkpart command.
</p>

<p>
You will need to create two partitions for Linux, one root filesystem and one 
swap partition. Run <c>mkpart primary START END</c> to create each partition,
replacing <c>START</c> and <c>END</c> with the desired megabyte boundries.
</p>

<p>
It is generally recommended that you create a swap partition that is two times
bigger than the amount of RAM in your computer, but at least 512Mb is 
recommended. To create the swap partition, run 
<c>mkpart primary linux-swap START END</c> with START and END again denoting
the partition boundries.
</p>

<p>
When you are done in parted simply type <c>quit</c>.
</p>

</body>
</section>
<section id="filesystems">
<title>Creating Filesystems</title>
<subsection>
<title>Introduction</title>
<body>

<p>
Now that your partitions are created, it is time to place a filesystem on them.
If you're not sure which filesystems to choose and are happy with our defaults,
continue with 
<uri link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
Otherwise, read on to learn about the available filesystems.
</p>

</body>
</subsection>
<subsection>
<title>Filesystems?</title>
<body>

<p>
Several filesystems are available for use on the PowerPC architecture including
ext2, ext3, ReiserFS and XFS, each with their strengths and faults.
</p>

<p>
<b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
journaling, which means that routine ext2 filesystem checks at startup time can
be quite time-consuming. There is now quite a selection of journaled 
filesystems that can be checked for consistency very quickly and are thus 
generally preferred over their non-journaled counterparts.
</p>

<p>
<b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
journaling for fast recovery in addition to other enhanced journaling modes
like full data and ordered data journaling. It uses a hashed B*-tree index that
enables high performance in almost all situations. In short, ext3 is a very
good and reliable filesystem and is highly recommended for most installs.
</p>

<p>
<b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
performance and greatly outperforms both ext2 and ext3 when dealing with small
files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
extremely well and has metadata journaling. ReiserFS is solid and usable as
both general-purpose filesystem and for extreme cases such as the creation of
large filesystems, very large files and directories containing tens of
thousands of small files.
</p>

<p>
<b>XFS</b> is a filesystem with metadata journaling which comes with a robust
feature-set and is optimized for scalability. We only recommend using this
filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
an uninterruptible power supply. Because XFS aggressively caches in-transit data
in RAM, improperly designed programs (those that don't take proper precautions
when writing files to disk and there are quite a few of them) can lose a good
deal of data if the system goes down unexpectedly.
</p>

</body>
</subsection>
<subsection>
<title>Activating the Swap Partition</title>
<body>

<p>
<c>mkswap</c> is the command that is used to initialize swap partitions:
</p>

<pre caption="Creating a swap signature">
# <i>mkswap /dev/hda3</i>
</pre>

<p>
To activate the swap partition, use <c>swapon</c>:
</p>

<pre caption="Activating the swap partition">
# <i>swapon /dev/hda3</i>
</pre>

<p>
Create and activate the swap now before creating other filesystems.
</p>

</body>
</subsection>
<subsection id="filesystems-apply">
<title>Applying a Filesystem to a Partition</title>
<body>

<p>
To create a filesystem on a partition or volume, there are tools available for 
each possible filesystem:
</p>

<table>
<tr>
  <th>Filesystem</th>
  <th>Creation Command</th>
</tr>
<tr>
  <ti>ext2</ti>
  <ti><c>mke2fs</c></ti>
</tr>
<tr>
  <ti>ext3</ti>
  <ti><c>mke2fs -j</c></ti>
</tr>
<tr>
  <ti>reiserfs</ti>
  <ti><c>mkreiserfs</c></ti>
</tr>
<tr>
  <ti>xfs</ti>
  <ti><c>mkfs.xfs</c></ti>
</tr>
</table>

<p>
For instance, to make an ext3 filesystem on the root partition 
(<path>/dev/hda4</path> in our example), you would use:
</p>

<pre caption="Applying a filesystem on a partition">
# <i>mke2fs -j /dev/hda4</i>
</pre>

<p>
Now create the filesystems on your newly created partitions (or logical
volumes).
</p>

<note>
On the PegasosII your partition which holds the kernel must be ext2, ext3 or
affs1.  NewWorld machines can boot from any of ext2, ext3, XFS, ReiserFS or
even HFS/HFS+ filesystems.  On OldWorld machines booting with BootX, the kernel
must be placed on an HFS partition, but this will be completed when you
configure your bootloader.
</note>

</body>
</subsection>
</section>
<section>
<title>Mounting</title>
<body>

<p>
Now that your partitions are initialized and are housing a filesystem, it is
time to mount those partitions. Use the <c>mount</c> command. As an example we
mount the root partition:
</p>

<pre caption="Mounting partitions">
# <i>mount /dev/hda4 /mnt/gentoo</i>
</pre>

<note>
If you want your <path>/tmp</path> to reside on a separate partition, be sure to
change its permissions after mounting and unpacking with
<c>chmod 1777 /mnt/gentoo/tmp</c>. This is also true for <path>/var/tmp</path>.
</note>

<p>
Continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
Installation Files</uri>.
</p>

</body>
</section>
</sections>