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<?xml version='1.0' encoding='UTF-8'?>
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<!DOCTYPE sections SYSTEM "/dtd/book.dtd">
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<!-- The content of this document is licensed under the CC-BY-SA license -->
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<!-- See http://creativecommons.org/licenses/by-sa/1.0 -->
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<!-- $Header: /home/cvsroot/gentoo/xml/htdocs/doc/en/handbook/draft/hb-install-ppc-disk.xml,v 1.1 2004/03/30 14:24:36 swift Exp $ -->
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<sections>
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<section>
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<title>Introduction to Block Devices</title>
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<subsection>
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<title>Block Devices</title>
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<body>
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<p>
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We'll take a good look at disk-oriented aspects of Gentoo Linux
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and Linux in general, including Linux filesystems, partitions and block devices.
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Then, once you're familiar with the ins and outs of disks and filesystems,
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you'll be guided through the process of setting up partitions and filesystems
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for your Gentoo Linux installation.
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</p>
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<p>
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To begin, we'll introduce <e>block devices</e>. The most famous block device is
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probably the one that represents the first IDE drive in a Linux system, namely
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<path>/dev/hda</path>. If your system uses SCSI drives, then your first hard
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drive would be <path>/dev/sda</path>.
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</p>
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<p>
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The block devices above represent an abstract interface to the disk. User
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programs can use these block devices to interact with your disk without worrying
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about whether your drives are IDE, SCSI or something else. The program can
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simply address the storage on the disk as a bunch of contiguous,
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randomly-accessible 512-byte blocks.
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</p>
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</body>
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</subsection>
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<subsection>
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<title>Partitions and Slices</title>
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<body>
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<p>
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Although it is theoretically possible to use a full disk to house your Linux
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system, this is almost never done in practice. Instead, full disk block devices
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are split up in smaller, more manageable block devices. On most systems,
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these are called <e>partitions</e>. Other architectures use a similar technique,
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called <e>slices</e>.
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</p>
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</body>
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</subsection>
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</section>
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<section>
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<title>Designing a Partitioning Scheme</title>
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<subsection>
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<title>Default Partitioning Scheme</title>
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<body>
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<p>
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If you are not interested in drawing up a partitioning scheme for your system,
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you can use the partitioning scheme we use throughout this book:
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</p>
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<table>
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<tr>
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<th>Partition NewWorld</th>
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<th>Partition OldWorld</th>
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<th>Filesystem</th>
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<th>Size</th>
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<th>Description</th>
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</tr>
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<tr>
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<ti><path>/dev/hda1</path></ti>
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<ti>(Not needed)</ti>
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<ti>(bootstrap)</ti>
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<ti>800k</ti>
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<ti>Apple_Bootstrap</ti>
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</tr>
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<tr>
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<ti><path>/dev/hda2</path></ti>
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<ti><path>/dev/hda1</path></ti>
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<ti>(swap)</ti>
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<ti>512M</ti>
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<ti>Swap partition</ti>
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</tr>
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<tr>
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<ti><path>/dev/hda3</path></ti>
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<ti><path>/dev/hda2</path></ti>
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<ti>ext3</ti>
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<ti>Rest of the disk</ti>
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<ti>Root partition</ti>
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</tr>
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</table>
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<p>
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If you are interested in knowing how big a partition should be, or even how
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many partitions you need, read on. Otherwise continue now with
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<uri link="#fdisk">Using fdisk to Partition your Disk</uri>.
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</p>
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</body>
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</subsection>
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<subsection>
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<title>How Many and How Big?</title>
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<body>
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<p>
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The number of partitions is highly dependent on your environment. For instance,
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if you have lots of users, you will most likely want to have your
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<path>/home</path> separate as it increases security and makes backups easier.
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If you are installing Gentoo to perform as a mailserver, your
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<path>/var</path> should be separate as all mails are stored inside
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<path>/var</path>. A good choice of filesystem will then maximise your
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performance. Gameservers will have a separate <path>/opt</path> as most gaming
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servers are installed there. The reason is similar for <path>/home</path>:
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security and backups.
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</p>
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<p>
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As you can see, it very much depends on what you want to achieve. Separate
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partitions or volumes have the following advantages:
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</p>
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<ul>
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<li>
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You can choose the most performant filesystem for each partition or volume
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</li>
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<li>
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Your entire system cannot run out of free space if one defunct tool is
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continuously writing files to a partition or volume
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</li>
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<li>
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If necessary, file system checks are reduced in time, as multiple checks can
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be done in parallel (although this advantage is more with multiple disks than
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it is with multiple partitions)
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</li>
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<li>
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Security can be enhanced by mounting some partitions or volumes read-only,
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nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
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</li>
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</ul>
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<p>
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However, multiple partitions have one big disadvantage: if not configured
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properly, you might result in having a system with lots
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of free space on one partition and none on another.
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</p>
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</body>
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</subsection>
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</section>
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<section>
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<title>Using mac-fdisk on PPC to Partition your Disk</title>
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<body>
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<p>
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At this point, create your partitions using <c>mac-fdisk</c>:
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</p>
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<pre caption="Starting mac-fdisk">
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# <i>mac-fdisk /dev/hda</i>
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</pre>
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<p>
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First delete the partitions you have cleared previously to make room for your
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Linux partitions. Use <c>d</c> in <c>mac-fdisk</c> to delete those partition(s).
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It will ask for the partition number to delete.
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</p>
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<p>
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Second, create an <e>Apple_Bootstrap</e> partition by using <c>b</c>. It will
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ask for what block you want to start. If you previously selected <c>3</c> as
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partition number, enter <c>3p</c>.
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</p>
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<note>
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This partition is <e>not</e> a "boot" partition. It is not used by Linux at all;
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you don't have to place any filesystem on it and you should never mount it. PPC
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users don't need a boot partition.
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</note>
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<p>
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Now create a swap partition by pressing <c>c</c>. Again <c>mac-fdisk</c> will
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ask for what block you want to start this partition from. As we used <c>3</c>
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before to create the Apple_Bootstrap partition, you now have to enter
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<c>4p</c>. When you're asked for the size, enter <c>512M</c> (or whatever size
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you want -- 512 is recommended though). When asked for a name, enter <c>swap</c>
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(mandatory).
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</p>
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<p>
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To create the root partition, enter <c>c</c>, followed by <c>5p</c> to select
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from what block the root partition should start. When asked for the size, enter
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<c>5p</c> again. <c>mac-fdisk</c> will interprete this as "Use all available
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space". When asked for the name, enter <c>root</c> (mandatory).
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</p>
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<p>
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To finish up, write the partition to the disk using <c>w</c> and <c>q</c> to
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quit <c>mac-fdisk</c>.
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</p>
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<p>
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Now that your partitions are created, you can now continue with <uri
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link="#filesystems">Creating Filesystems</uri>.
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</p>
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</body>
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</section>
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<section id="filesystems">
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<title>Creating Filesystems</title>
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<subsection>
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<title>Introduction</title>
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<body>
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<p>
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Now that your partitions are created, it is time to place a filesystem on them.
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If you don't care about what filesystem to choose and are happy with what we use
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as default in this handbook, continue with <uri
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link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
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Otherwise read on to learn about the available filesystems...
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</p>
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</body>
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</subsection>
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<subsection>
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<title>Filesystems?</title>
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<body>
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<p>
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Several filesystems are available. Ext2 and ext3 are found stable on the
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PPC architecture, reiserfs and xfs are in experimental stage. jfs is
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unsupported.
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</p>
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<p>
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<b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
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journaling, which means that routine ext2 filesystem checks at startup time can
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be quite time-consuming. There is now quite a selection of newer-generation
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journaled filesystems that can be checked for consistency very quickly and are
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thus generally preferred over their non-journaled counterparts. Journaled
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filesystems prevent long delays when you boot your system and your filesystem
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happens to be in an inconsistent state.
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</p>
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<p>
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<b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
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journaling for fast recovery in addition to other enhanced journaling modes like
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full data and ordered data journaling. ext3 is a very good and reliable
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filesystem. It has an additional hashed b-tree indexing option that enables
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high performance in almost all situations. In short, ext3 is an excellent
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filesystem.
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</p>
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<p>
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<b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
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performance and greatly outperforms both ext2 and ext3 when dealing with small
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files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
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extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
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solid and usable as both general-purpose filesystem and for extreme cases such
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as the creation of large filesystems, the use of many small files, very large
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files and directories containing tens of thousands of files.
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</p>
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<p>
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<b>XFS</b> is a filesystem with metadata journaling that is fully supported
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under Gentoo Linux's xfs-sources kernel. It comes with a robust feature-set and
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is optimized for scalability. We only recommend using this filesystem on Linux
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systems with high-end SCSI and/or fibre channel storage and a uninterruptible
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power supply. Because XFS aggressively caches in-transit data in RAM, improperly
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designed programs (those that don't take proper precautions when writing files
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to disk and there are quite a few of them) can lose a good deal of data if the
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system goes down unexpectedly.
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</p>
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<p>
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<b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
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become production-ready and there hasn't been a sufficient track record to
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comment positively nor negatively on its general stability at this point.
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</p>
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</body>
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</subsection>
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<subsection id="filesystems-apply">
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<title>Applying a Filesystem to a Partition</title>
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<body>
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<p>
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To create a filesystem on a partition or volume, there are tools available for
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each possible filesystem:
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</p>
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<table>
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<tr>
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<th>Filesystem</th>
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<th>Creation Command</th>
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</tr>
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<tr>
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<ti>ext2</ti>
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<ti><c>mke2fs</c></ti>
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</tr>
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<tr>
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<ti>ext3</ti>
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<ti><c>mke2fs -j</c></ti>
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</tr>
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<tr>
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<ti>reiserfs</ti>
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<ti><c>mkreiserfs</c></ti>
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</tr>
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<tr>
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<ti>xfs</ti>
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<ti><c>mkfs.xfs</c></ti>
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</tr>
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<tr>
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<ti>jfs</ti>
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<ti><c>mkfs.jfs</c></ti>
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</tr>
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</table>
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<p>
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For instance, to have the root partition (<path>/dev/hda3</path> in our example)
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in ext3 (as in our example), you would use:
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</p>
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<pre caption="Applying a filesystem on a partition">
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# <i>mke2fs -j /dev/hda3</i>
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</pre>
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<p>
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Now create the filesystems on your newly created partitions (or logical
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volumes).
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</p>
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</body>
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</subsection>
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<subsection>
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<title>Activating the Swap Partition</title>
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<body>
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<p>
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<c>mkswap</c> is the command that is used to initialize swap partitions:
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</p>
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<pre caption="Creating a Swap signature">
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# <i>mkswap /dev/hda2</i>
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</pre>
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<p>
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To activate the swap partition, use <c>swapon</c>:
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</p>
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<pre caption="Activating the swap partition">
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# <i>swapon /dev/hda2</i>
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</pre>
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<p>
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Create and activate the swap now.
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</p>
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</body>
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</subsection>
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</section>
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<section>
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<title>Mounting</title>
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<body>
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<p>
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Now that your partitions are initialized and are housing a filesystem, it is
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time to mount those partitions. Use the <c>mount</c> command. Don't forget to
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create the necessary mount directories for every partition you created. As an
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example we mount the root and boot partition:
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</p>
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<pre caption="Mounting partitions">
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# <i>mount /dev/hda3 /mnt/gentoo</i>
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</pre>
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<note>
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If you want your <path>/tmp</path> to reside on a separate partition, be sure to
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change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
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also holds for <path>/var/tmp</path>.
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</note>
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<p>
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We also need to mount the proc filesystem (a virtual interface with the kernel)
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on <path>/proc</path>. We first create the <path>/mnt/gentoo/proc</path>
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mountpoint and then mount the filesystem:
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</p>
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<pre caption="Creating the /mnt/gentoo/proc mountpoint">
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# <i>mkdir /mnt/gentoo/proc</i>
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# <i>mount -t proc none /mnt/gentoo/proc</i>
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</pre>
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<p>
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Now continue with <uri link="?part=1&chap=5">Installing the Gentoo
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Installation Files</uri>.
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</p>
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</body>
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</section>
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</sections>
|
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