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1 <?xml version='1.0' encoding='UTF-8'?>
2 <!DOCTYPE sections SYSTEM "/dtd/book.dtd">
4 <!-- The content of this document is licensed under the CC-BY-SA license -->
5 <!-- See http://creativecommons.org/licenses/by-sa/1.0 -->
7 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/draft/hb-install-ppc-disk.xml,v 1.6 2004/07/19 01:22:49 pylon Exp $ -->
9 <sections>
10 <section>
11 <title>Introduction to Block Devices</title>
12 <subsection>
13 <title>Block Devices</title>
14 <body>
16 <p>
17 We'll take a good look at disk-oriented aspects of Gentoo Linux
18 and Linux in general, including Linux filesystems, partitions and block devices.
19 Then, once you're familiar with the ins and outs of disks and filesystems,
20 you'll be guided through the process of setting up partitions and filesystems
21 for your Gentoo Linux installation.
22 </p>
24 <p>
25 To begin, we'll introduce <e>block devices</e>. The most famous block device is
26 probably the one that represents the first IDE drive in a Linux system, namely
27 <path>/dev/hda</path>. If your system uses SCSI drives, then your first hard
28 drive would be <path>/dev/sda</path>.
29 </p>
31 <p>
32 The block devices above represent an abstract interface to the disk. User
33 programs can use these block devices to interact with your disk without worrying
34 about whether your drives are IDE, SCSI or something else. The program can
35 simply address the storage on the disk as a bunch of contiguous,
36 randomly-accessible 512-byte blocks.
37 </p>
39 </body>
40 </subsection>
41 <subsection>
42 <title>Partitions and Slices</title>
43 <body>
45 <p>
46 Although it is theoretically possible to use a full disk to house your Linux
47 system, this is almost never done in practice. Instead, full disk block devices
48 are split up in smaller, more manageable block devices. On most systems,
49 these are called <e>partitions</e>. Other architectures use a similar technique,
50 called <e>slices</e>.
51 </p>
53 </body>
54 </subsection>
55 </section>
56 <section>
57 <title>Designing a Partitioning Scheme</title>
58 <subsection>
59 <title>Default Partitioning Scheme</title>
60 <body>
62 <p>
63 If you are not interested in drawing up a partitioning scheme for your system,
64 you can use the partitioning scheme we use throughout this book:
65 </p>
67 <table>
68 <tr>
69 <th>Partition NewWorld</th>
70 <th>Partition OldWorld</th>
71 <th>Partition Pegasos</th>
72 <th>Filesystem</th>
73 <th>Size</th>
74 <th>Description</th>
75 </tr>
76 <tr>
77 <ti><path>/dev/hda1</path></ti>
78 <ti>(Not needed)</ti>
79 <ti>(Not applicable)</ti>
80 <ti>(bootstrap)</ti>
81 <ti>800k</ti>
82 <ti>Apple_Bootstrap</ti>
83 </tr>
84 <tr>
85 <ti><path>/dev/hda2</path></ti>
86 <ti><path>/dev/hda1</path></ti>
87 <ti><path>/dev/hda1</path></ti>
88 <ti>(swap)</ti>
89 <ti>512M</ti>
90 <ti>Swap partition</ti>
91 </tr>
92 <tr>
93 <ti><path>/dev/hda3</path></ti>
94 <ti><path>/dev/hda2</path></ti>
95 <ti><path>/dev/hda2</path></ti>
96 <ti>ext3</ti>
97 <ti>Rest of the disk</ti>
98 <ti>Root partition</ti>
99 </tr>
100 </table>
102 <p>
103 If you are interested in knowing how big a partition should be, or even how
104 many partitions you need, read on. Otherwise continue now with
105 <uri link="#fdisk">Default: Using mac-fdisk (Apple/IBM) to Partition your
106 Disk</uri> or <uri link="#parted">Alternative: Using parted (especially Pegasos) to
107 Partition your Disk</uri>.
108 </p>
110 </body>
111 </subsection>
112 <subsection>
113 <title>How Many and How Big?</title>
114 <body>
116 <p>
117 The number of partitions is highly dependent on your environment. For instance,
118 if you have lots of users, you will most likely want to have your
119 <path>/home</path> separate as it increases security and makes backups easier.
120 If you are installing Gentoo to perform as a mailserver, your
121 <path>/var</path> should be separate as all mails are stored inside
122 <path>/var</path>. A good choice of filesystem will then maximise your
123 performance. Gameservers will have a separate <path>/opt</path> as most gaming
124 servers are installed there. The reason is similar for <path>/home</path>:
125 security and backups.
126 </p>
128 <p>
129 As you can see, it very much depends on what you want to achieve. Separate
130 partitions or volumes have the following advantages:
131 </p>
133 <ul>
134 <li>
135 You can choose the best performing filesystem for each partition or volume
136 </li>
137 <li>
138 Your entire system cannot run out of free space if one defunct tool is
139 continuously writing files to a partition or volume
140 </li>
141 <li>
142 If necessary, file system checks are reduced in time, as multiple checks can
143 be done in parallel (although this advantage is more with multiple disks than
144 it is with multiple partitions)
145 </li>
146 <li>
147 Security can be enhanced by mounting some partitions or volumes read-only,
148 nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
149 </li>
150 </ul>
152 <p>
153 However, multiple partitions have one big disadvantage: if not configured
154 properly, you might result in having a system with lots
155 of free space on one partition and none on another.
156 </p>
158 </body>
159 </subsection>
160 </section>
161 <section id="fdisk">
162 <title>Default: Using mac-fdisk (Apple/IBM) Partition your Disk</title>
163 <body>
165 <p>
166 At this point, create your partitions using <c>mac-fdisk</c>:
167 </p>
169 <pre caption="Starting mac-fdisk">
170 # <i>mac-fdisk /dev/hda</i>
171 </pre>
173 <p>
174 First delete the partitions you have cleared previously to make room for your
175 Linux partitions. Use <c>d</c> in <c>mac-fdisk</c> to delete those partition(s).
176 It will ask for the partition number to delete.
177 </p>
179 <p>
180 Second, create an <e>Apple_Bootstrap</e> partition by using <c>b</c>. It will
181 ask for what block you want to start. Enter the number of your first free
182 partition, followed by a <c>p</c>. For instance this is <c>1p</c>.
183 </p>
185 <note>
186 This partition is <e>not</e> a "boot" partition. It is not used by Linux at all;
187 you don't have to place any filesystem on it and you should never mount it. PPC
188 users don't need a an extra partition for <path>/boot</path>.
189 </note>
191 <p>
192 Now create a swap partition by pressing <c>c</c>. Again <c>mac-fdisk</c> will
193 ask for what block you want to start this partition from. As we used <c>1</c>
194 before to create the Apple_Bootstrap partition, you now have to enter
195 <c>2p</c>. When you're asked for the size, enter <c>512M</c> (or whatever size
196 you want -- 512MB is recommended though). When asked for a name, enter <c>swap</c>
197 (mandatory).
198 </p>
200 <p>
201 To create the root partition, enter <c>c</c>, followed by <c>3p</c> to select
202 from what block the root partition should start. When asked for the size, enter
203 <c>3p</c> again. <c>mac-fdisk</c> will interpret this as "Use all available
204 space". When asked for the name, enter <c>root</c> (mandatory).
205 </p>
207 <p>
208 To finish up, write the partition to the disk using <c>w</c> and <c>q</c> to
209 quit <c>mac-fdisk</c>.
210 </p>
212 <p>
213 Now that your partitions are created, you can now continue with <uri
214 link="#filesystems">Creating Filesystems</uri>.
215 </p>
217 </body>
218 </section>
219 <section id="parted">
220 <title>Using parted (especially Pegasos) to Partition your Disk</title>
221 <body>
223 <p>
224 <c>parted</c>, the Partition Editor, can now handle HFS+ partitions used by
225 Mac OS and Mac OS X. With this tool you can shrink your Mac-partitions and
226 create space for your Linux partitions. Nevertheless, the example below
227 describes partitioning for Pegasos machines only.
228 </p>
230 <p>
231 To begin let's fire up <c>parted</c>:
232 </p>
234 <pre caption="Starting parted">
235 # <i>parted /dev/hda</i>
236 </pre>
238 <p>
239 If the drive is unpartitioned, run <c>mklabel amiga</c> to create a new
240 disklabel for the drive.
241 </p>
243 <p>
244 You can type <c>print</c> at any time in parted to display the current partition
245 table. Your changes aren't saved until you quit the application; if at any time
246 you change your mind or made a mistake you can press <c>Ctrl-c</c> to abort
247 parted.
248 </p>
250 <p>
251 If you intend to also install MorphOS on your Pegasos create an affs1 filesystem
252 named "BI0" (BI zero) at the start of the drive. 50MB should be more than enough
253 to store the MorphOS kernel. If you have a Pegasos I or intend to use reiserfs,
254 xfs or jfs you will also have to store your Linux kernel on this partition (the
255 Pegasos II can boot from ext2/ext3 drives). To create the partition run
256 <c>mkpart primary affs1 START END</c> where <c>START</c> and <c>END</c> should
257 be replaced with the megabyte range (f.i. <c>5 55</c> creates a 50 MB partition
258 starting at 5MB and ending at 55MB.
259 </p>
261 <p>
262 You need to create two partitions for Linux, one root filesystem for all your
263 program files etc, and one swap partition. To create the root filesystem you
264 must first decide which filesystem to use. Possible options are ext2, ext3,
265 reiserfs, jfs and xfs. Unless you know what you are doing, use ext3. Run
266 <c>mkpart primary ext3 START END</c> to create an ext3 partition. Again, replace
267 <c>START</c> and <c>END</c> with the megabyte start and stop marks for the
268 partition.
269 </p>
271 <p>
272 It is generally recommended that you create a swap partition the same size as
273 the amount of RAM in your computer times two. You will probably get away with a
274 smaller swap partition unless you intend to run a lot of applications at the
275 same time (although at least 512MB is recommended). To create the swap
276 partition, run <c>mkpart primary linux-swap START END</c>.
277 </p>
279 <p>
280 Write down the partition minor numbers as they are required during the
281 installation process. To dislay the minor numbers run <c>print</c>. Your drives
282 are accessed as <path>/dev/hdaX</path> where X is replaced with the minor number
283 of the partition.
284 </p>
286 <p>
287 When you are done in parted simply run <c>quit</c>.
288 </p>
290 </body>
291 </section>
292 <section id="filesystems">
293 <title>Creating Filesystems</title>
294 <subsection>
295 <title>Introduction</title>
296 <body>
298 <p>
299 Now that your partitions are created, it is time to place a filesystem on them.
300 If you don't care about what filesystem to choose and are happy with what we use
301 as default in this handbook, continue with <uri
302 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
303 Otherwise read on to learn about the available filesystems...
304 </p>
306 </body>
307 </subsection>
308 <subsection>
309 <title>Filesystems?</title>
310 <body>
312 <p>
313 Several filesystems are available. ext2 and ext3 are found stable on the
314 PPC architecture, reiserfs and xfs are in testing stage, though we did not
315 encountered any serious errors with the 2.6 Linux kernel. jfs is
316 unsupported.
317 </p>
319 <p>
320 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
321 journaling, which means that routine ext2 filesystem checks at startup time can
322 be quite time-consuming. There is now quite a selection of newer-generation
323 journaled filesystems that can be checked for consistency very quickly and are
324 thus generally preferred over their non-journaled counterparts. Journaled
325 filesystems prevent long delays when you boot your system and your filesystem
326 happens to be in an inconsistent state.
327 </p>
329 <p>
330 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
331 journaling for fast recovery in addition to other enhanced journaling modes like
332 full data and ordered data journaling. ext3 is a very good and reliable
333 filesystem. It has an additional hashed b-tree indexing option that enables
334 high performance in almost all situations. In short, ext3 is an excellent
335 filesystem.
336 </p>
338 <p>
339 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
340 performance and greatly outperforms both ext2 and ext3 when dealing with small
341 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
342 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
343 solid and usable as both general-purpose filesystem and for extreme cases such
344 as the creation of large filesystems, the use of many small files, very large
345 files and directories containing tens of thousands of files.
346 </p>
348 <p>
349 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
350 feature-set and is optimized for scalability. We only recommend using this
351 filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
352 an uninterruptible power supply. Because XFS aggressively caches in-transit data
353 in RAM, improperly designed programs (those that don't take proper precautions
354 when writing files to disk and there are quite a few of them) can lose a good
355 deal of data if the system goes down unexpectedly.
356 </p>
358 <p>
359 <b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
360 become production-ready and there hasn't been a sufficient track record to
361 comment positively nor negatively on its general stability at this point.
362 </p>
364 </body>
365 </subsection>
366 <subsection id="filesystems-apply">
367 <title>Applying a Filesystem to a Partition</title>
368 <body>
370 <p>
371 To create a filesystem on a partition or volume, there are tools available for
372 each possible filesystem:
373 </p>
375 <table>
376 <tr>
377 <th>Filesystem</th>
378 <th>Creation Command</th>
379 </tr>
380 <tr>
381 <ti>ext2</ti>
382 <ti><c>mke2fs</c></ti>
383 </tr>
384 <tr>
385 <ti>ext3</ti>
386 <ti><c>mke2fs -j</c></ti>
387 </tr>
388 <tr>
389 <ti>reiserfs</ti>
390 <ti><c>mkreiserfs</c></ti>
391 </tr>
392 <tr>
393 <ti>xfs</ti>
394 <ti><c>mkfs.xfs</c></ti>
395 </tr>
396 <tr>
397 <ti>jfs</ti>
398 <ti><c>mkfs.jfs</c></ti>
399 </tr>
400 </table>
402 <p>
403 For instance, to have the root partition (<path>/dev/hda3</path> in our example)
404 in ext3 (as in our example), you would use:
405 </p>
407 <pre caption="Applying a filesystem on a partition">
408 # <i>mke2fs -j /dev/hda3</i>
409 </pre>
411 <p>
412 Now create the filesystems on your newly created partitions (or logical
413 volumes).
414 </p>
416 <note>
417 Be sure that the partition which will host your kernel (the
418 <path>/boot</path>-path) must be ext2 or ext3. The bootloader can only handle
419 this filesystem.
420 </note>
422 </body>
423 </subsection>
424 <subsection>
425 <title>Activating the Swap Partition</title>
426 <body>
428 <p>
429 <c>mkswap</c> is the command that is used to initialize swap partitions:
430 </p>
432 <pre caption="Creating a Swap signature">
433 # <i>mkswap /dev/hda2</i>
434 </pre>
436 <p>
437 To activate the swap partition, use <c>swapon</c>:
438 </p>
440 <pre caption="Activating the swap partition">
441 # <i>swapon /dev/hda2</i>
442 </pre>
444 <p>
445 Create and activate the swap now.
446 </p>
448 </body>
449 </subsection>
450 </section>
451 <section>
452 <title>Mounting</title>
453 <body>
455 <p>
456 Now that your partitions are initialized and are housing a filesystem, it is
457 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
458 create the necessary mount directories for every partition you created. As an
459 example we create a mount-point and mount the root and boot partition:
460 </p>
462 <pre caption="Mounting partitions">
463 # <i>mkdir /mnt/gentoo</i>
464 # <i>mount /dev/hda3 /mnt/gentoo</i>
465 </pre>
467 <note>
468 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
469 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
470 also holds for <path>/var/tmp</path>.
471 </note>
473 <p>
474 We also need to mount the proc filesystem (a virtual interface with the kernel)
475 on <path>/proc</path>. We first create the <path>/mnt/gentoo/proc</path>
476 mountpoint and then mount the filesystem:
477 </p>
479 <pre caption="Creating the /mnt/gentoo/proc mountpoint">
480 # <i>mkdir /mnt/gentoo/proc</i>
481 # <i>mount -t proc none /mnt/gentoo/proc</i>
482 </pre>
484 <p>
485 Finally we have to create the <path>/dev</path> files in our new home, which is
486 needed during the bootloader installation. This could be done by "bind"-mapping
487 the <path>/dev</path>-filesystem from the LiveCD:
488 </p>
490 <pre caption="Bind-mounting the /dev-filesystem">
491 # <i>mkdir /mnt/gentoo/dev</i>
492 # <i>mount -o bind /dev /mnt/gentoo/dev</i>
493 </pre>
495 <p>
496 Now continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
497 Installation Files</uri>.
498 </p>
500 </body>
501 </section>
502 </sections>

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