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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: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-install-hppa-disk.xml,v 1.9 2004/09/30 03:14:57 vapier Exp $ -->
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<sections>
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<version>1.9</version>
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<date>September 30, 2004</date>
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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 SCSI HD in a Linux system, namely
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<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>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 best performing 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. There is also a 15-partition
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limit for SCSI and SATA.
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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 fdisk on HPPA to Partition your Disk</title>
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<body>
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<p>
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Use <c>fdisk</c> to create the partitions you want:
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</p>
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<pre caption="Partitioning the disk">
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# <i>fdisk /dev/sda</i>
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</pre>
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<p>
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HPPA machines use the PC standard DOS partition tables. To create a new
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DOS partition table, simply use the <c>o</c> command.
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</p>
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<pre caption="Creating a DOS partition table">
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# <i>fdisk /dev/sda</i>
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Command (m for help): <i>o</i>
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Building a new DOS disklabel.
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</pre>
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<p>
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PALO (the HPPA bootloader) needs a special partition to work. You have
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to create a partition of at least 16Mb at the beginning of your disk.
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The partition type must be of type <e>f0</e> (Linux/PA-RISC boot).
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</p>
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<impo>
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If you ignore this and continue without a special PALO partition, your system
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will stop loving you and fail to start. Also, if your disk is larger than 2Gb,
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make sure that the boot partition is in the first 2Gb of your disk. PALO is
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unable to read a kernel after the 2Gb limit.
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</impo>
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<pre caption="A simple default partition schema">
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# <i>cat /etc/fstab</i>
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/dev/sda2 /boot ext3 noauto,noatime 1 1
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/dev/sda3 none swap sw 0 0
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/dev/sda4 / ext3 noatime 0 0
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# <i>fdisk /dev/sda</i>
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Command (m for help): <i>p</i>
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Disk /dev/sda: 4294 MB, 4294816768 bytes
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133 heads, 62 sectors/track, 1017 cylinders
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Units = cylinders of 8246 * 512 = 4221952 bytes
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Device Boot Start End Blocks Id System
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/dev/sda1 1 8 32953 f0 Linux/PA-RISC boot
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/dev/sda2 9 20 49476 83 Linux
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/dev/sda3 21 70 206150 82 Linux swap
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/dev/sda4 71 1017 3904481 83 Linux
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</pre>
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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, ext3, XFS and reiserfs are found stable on
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the HPPA architecture. The others are very experimental.
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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 which comes with a robust
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feature-set and is optimized for scalability. We only recommend using this
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filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
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an uninterruptible power supply. Because XFS aggressively caches in-transit data
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in RAM, improperly designed programs (those that don't take proper precautions
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when writing files to disk and there are quite a few of them) can lose a good
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deal of data if the 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 boot partition (<path>/dev/sda2</path> in our
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example) in ext2 and the root partition (<path>/dev/sda4</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 /dev/sda2</i>
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# <i>mke2fs -j /dev/sda4</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/sda3</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/sda3</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/sda4 /mnt/gentoo</i>
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# <i>mkdir /mnt/gentoo/boot</i>
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# <i>mount /dev/sda2 /mnt/gentoo/boot</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 will also have to mount the proc filesystem (a virtual interface with the
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kernel) on <path>/proc</path>. But first we will need to place our files on the partitions.
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</p>
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<p>
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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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