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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/hb-install-ppc-disk.xml,v 1.16 2004/09/14 11:55:12 swift 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>32k</ti>
82 <ti>Apple_partition_map</ti>
83 </tr>
84 <tr>
85 <ti><path>/dev/hda2</path></ti>
86 <ti>(Not needed)</ti>
87 <ti>(Not applicable)</ti>
88 <ti>(bootstrap)</ti>
89 <ti>800k</ti>
90 <ti>Apple_Bootstrap</ti>
91 </tr>
92 <tr>
93 <ti><path>/dev/hda3</path></ti>
94 <ti><path>/dev/hda1</path></ti>
95 <ti><path>/dev/hda1</path></ti>
96 <ti>(swap)</ti>
97 <ti>512M</ti>
98 <ti>Swap partition</ti>
99 </tr>
100 <tr>
101 <ti><path>/dev/hda4</path></ti>
102 <ti><path>/dev/hda2</path></ti>
103 <ti><path>/dev/hda2</path></ti>
104 <ti>ext3</ti>
105 <ti>Rest of the disk</ti>
106 <ti>Root partition</ti>
107 </tr>
108 </table>
110 <p>
111 If you are interested in knowing how big a partition should be, or even how
112 many partitions you need, read on. Otherwise continue now with
113 <uri link="#fdisk">Default: Using mac-fdisk (Apple/IBM) to Partition your
114 Disk</uri> or <uri link="#parted">Alternative: Using parted (especially Pegasos) to
115 Partition your Disk</uri>.
116 </p>
118 </body>
119 </subsection>
120 <subsection>
121 <title>How Many and How Big?</title>
122 <body>
124 <p>
125 The number of partitions is highly dependent on your environment. For instance,
126 if you have lots of users, you will most likely want to have your
127 <path>/home</path> separate as it increases security and makes backups easier.
128 If you are installing Gentoo to perform as a mailserver, your
129 <path>/var</path> should be separate as all mails are stored inside
130 <path>/var</path>. A good choice of filesystem will then maximise your
131 performance. Gameservers will have a separate <path>/opt</path> as most gaming
132 servers are installed there. The reason is similar for <path>/home</path>:
133 security and backups.
134 </p>
136 <p>
137 As you can see, it very much depends on what you want to achieve. Separate
138 partitions or volumes have the following advantages:
139 </p>
141 <ul>
142 <li>
143 You can choose the best performing filesystem for each partition or volume
144 </li>
145 <li>
146 Your entire system cannot run out of free space if one defunct tool is
147 continuously writing files to a partition or volume
148 </li>
149 <li>
150 If necessary, file system checks are reduced in time, as multiple checks can
151 be done in parallel (although this advantage is more with multiple disks than
152 it is with multiple partitions)
153 </li>
154 <li>
155 Security can be enhanced by mounting some partitions or volumes read-only,
156 nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
157 </li>
158 </ul>
160 <p>
161 However, multiple partitions have one big disadvantage: if not configured
162 properly, you might result in having a system with lots
163 of free space on one partition and none on another. There is also a 15-partition
164 limit for SCSI and SATA.
165 </p>
167 </body>
168 </subsection>
169 </section>
170 <section id="fdisk">
171 <title>Default: Using mac-fdisk (Apple/IBM) Partition your Disk</title>
172 <body>
174 <p>
175 At this point, create your partitions using <c>mac-fdisk</c>:
176 </p>
178 <pre caption="Starting mac-fdisk">
179 # <i>mac-fdisk /dev/hda</i>
180 </pre>
182 <p>
183 First delete the partitions you have cleared previously to make room for your
184 Linux partitions. Use <c>d</c> in <c>mac-fdisk</c> to delete those partition(s).
185 It will ask for the partition number to delete.
186 </p>
188 <p>
189 Second, create an <e>Apple_Bootstrap</e> partition by using <c>b</c>. It will
190 ask for what block you want to start. Enter the number of your first free
191 partition, followed by a <c>p</c>. For instance this is <c>1p</c>.
192 </p>
194 <note>
195 This partition is <e>not</e> a "boot" partition. It is not used by Linux at all;
196 you don't have to place any filesystem on it and you should never mount it. PPC
197 users don't need a an extra partition for <path>/boot</path>.
198 </note>
200 <p>
201 Now create a swap partition by pressing <c>c</c>. Again <c>mac-fdisk</c> will
202 ask for what block you want to start this partition from. As we used <c>1</c>
203 before to create the Apple_Bootstrap partition, you now have to enter
204 <c>2p</c>. When you're asked for the size, enter <c>512M</c> (or whatever size
205 you want -- 512MB is recommended though). When asked for a name, enter <c>swap</c>
206 (mandatory).
207 </p>
209 <p>
210 To create the root partition, enter <c>c</c>, followed by <c>3p</c> to select
211 from what block the root partition should start. When asked for the size, enter
212 <c>3p</c> again. <c>mac-fdisk</c> will interpret this as "Use all available
213 space". When asked for the name, enter <c>root</c> (mandatory).
214 </p>
216 <p>
217 To finish up, write the partition to the disk using <c>w</c> and <c>q</c> to
218 quit <c>mac-fdisk</c>.
219 </p>
221 <p>
222 Now that your partitions are created, you can now continue with <uri
223 link="#filesystems">Creating Filesystems</uri>.
224 </p>
226 </body>
227 </section>
228 <section id="parted">
229 <title>Using parted (especially Pegasos) to Partition your Disk</title>
230 <body>
232 <p>
233 <c>parted</c>, the Partition Editor, can now handle HFS+ partitions used by
234 Mac OS and Mac OS X. With this tool you can shrink your Mac-partitions and
235 create space for your Linux partitions. Nevertheless, the example below
236 describes partitioning for Pegasos machines only.
237 </p>
239 <p>
240 To begin let's fire up <c>parted</c>:
241 </p>
243 <pre caption="Starting parted">
244 # <i>parted /dev/hda</i>
245 </pre>
247 <p>
248 If the drive is unpartitioned, run <c>mklabel amiga</c> to create a new
249 disklabel for the drive.
250 </p>
252 <p>
253 You can type <c>print</c> at any time in parted to display the current partition
254 table. Your changes aren't saved until you quit the application; if at any time
255 you change your mind or made a mistake you can press <c>Ctrl-c</c> to abort
256 parted.
257 </p>
259 <p>
260 If you intend to also install MorphOS on your Pegasos create an affs1 filesystem
261 named "BI0" (BI zero) at the start of the drive. 50MB should be more than enough
262 to store the MorphOS kernel. If you have a Pegasos I or intend to use reiserfs or
263 xfs, you will also have to store your Linux kernel on this partition (the
264 Pegasos II can boot from ext2/ext3 drives). To create the partition run
265 <c>mkpart primary affs1 START END</c> where <c>START</c> and <c>END</c> should
266 be replaced with the megabyte range (f.i. <c>5 55</c> creates a 50 MB partition
267 starting at 5MB and ending at 55MB.
268 </p>
270 <p>
271 You need to create two partitions for Linux, one root filesystem for all your
272 program files etc, and one swap partition. To create the root filesystem you
273 must first decide which filesystem to use. Possible options are ext2, ext3,
274 reiserfs and xfs. Unless you know what you are doing, use ext3. Run
275 <c>mkpart primary ext3 START END</c> to create an ext3 partition. Again, replace
276 <c>START</c> and <c>END</c> with the megabyte start and stop marks for the
277 partition.
278 </p>
280 <p>
281 It is generally recommended that you create a swap partition the same size as
282 the amount of RAM in your computer times two. You will probably get away with a
283 smaller swap partition unless you intend to run a lot of applications at the
284 same time (although at least 512MB is recommended). To create the swap
285 partition, run <c>mkpart primary linux-swap START END</c>.
286 </p>
288 <p>
289 Write down the partition minor numbers as they are required during the
290 installation process. To dislay the minor numbers run <c>print</c>. Your drives
291 are accessed as <path>/dev/hdaX</path> where X is replaced with the minor number
292 of the partition.
293 </p>
295 <p>
296 When you are done in parted simply run <c>quit</c>.
297 </p>
299 </body>
300 </section>
301 <section id="filesystems">
302 <title>Creating Filesystems</title>
303 <subsection>
304 <title>Introduction</title>
305 <body>
307 <p>
308 Now that your partitions are created, it is time to place a filesystem on them.
309 If you don't care about what filesystem to choose and are happy with what we use
310 as default in this handbook, continue with <uri
311 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
312 Otherwise read on to learn about the available filesystems...
313 </p>
315 </body>
316 </subsection>
317 <subsection>
318 <title>Filesystems?</title>
319 <body>
321 <p>
322 Several filesystems are available. ext2, ext3, reiserfs and xfs are found stable
323 on the PPC architecture. jfs is unsupported.
324 </p>
326 <p>
327 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
328 journaling, which means that routine ext2 filesystem checks at startup time can
329 be quite time-consuming. There is now quite a selection of newer-generation
330 journaled filesystems that can be checked for consistency very quickly and are
331 thus generally preferred over their non-journaled counterparts. Journaled
332 filesystems prevent long delays when you boot your system and your filesystem
333 happens to be in an inconsistent state.
334 </p>
336 <p>
337 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
338 journaling for fast recovery in addition to other enhanced journaling modes like
339 full data and ordered data journaling. ext3 is a very good and reliable
340 filesystem. It has an additional hashed b-tree indexing option that enables
341 high performance in almost all situations. In short, ext3 is an excellent
342 filesystem.
343 </p>
345 <p>
346 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
347 performance and greatly outperforms both ext2 and ext3 when dealing with small
348 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
349 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
350 solid and usable as both general-purpose filesystem and for extreme cases such
351 as the creation of large filesystems, the use of many small files, very large
352 files and directories containing tens of thousands of files.
353 </p>
355 <p>
356 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
357 feature-set and is optimized for scalability. We only recommend using this
358 filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
359 an uninterruptible power supply. Because XFS aggressively caches in-transit data
360 in RAM, improperly designed programs (those that don't take proper precautions
361 when writing files to disk and there are quite a few of them) can lose a good
362 deal of data if the system goes down unexpectedly.
363 </p>
365 </body>
366 </subsection>
367 <subsection id="filesystems-apply">
368 <title>Applying a Filesystem to a Partition</title>
369 <body>
371 <p>
372 To create a filesystem on a partition or volume, there are tools available for
373 each possible filesystem:
374 </p>
376 <table>
377 <tr>
378 <th>Filesystem</th>
379 <th>Creation Command</th>
380 </tr>
381 <tr>
382 <ti>ext2</ti>
383 <ti><c>mke2fs</c></ti>
384 </tr>
385 <tr>
386 <ti>ext3</ti>
387 <ti><c>mke2fs -j</c></ti>
388 </tr>
389 <tr>
390 <ti>reiserfs</ti>
391 <ti><c>mkreiserfs</c></ti>
392 </tr>
393 <tr>
394 <ti>xfs</ti>
395 <ti><c>mkfs.xfs</c></ti>
396 </tr>
397 </table>
399 <p>
400 For instance, to have the root partition (<path>/dev/hda3</path> in our example)
401 in ext3 (as in our example), you would use:
402 </p>
404 <pre caption="Applying a filesystem on a partition">
405 # <i>mke2fs -j /dev/hda3</i>
406 </pre>
408 <p>
409 Now create the filesystems on your newly created partitions (or logical
410 volumes).
411 </p>
413 <note>
414 Be sure that the partition which will host your kernel (the
415 <path>/boot</path>-path) must be ext2 or ext3. The bootloader can only handle
416 this filesystem.
417 </note>
419 </body>
420 </subsection>
421 <subsection>
422 <title>Activating the Swap Partition</title>
423 <body>
425 <p>
426 <c>mkswap</c> is the command that is used to initialize swap partitions:
427 </p>
429 <pre caption="Creating a Swap signature">
430 # <i>mkswap /dev/hda2</i>
431 </pre>
433 <p>
434 To activate the swap partition, use <c>swapon</c>:
435 </p>
437 <pre caption="Activating the swap partition">
438 # <i>swapon /dev/hda2</i>
439 </pre>
441 <p>
442 Create and activate the swap now.
443 </p>
445 </body>
446 </subsection>
447 </section>
448 <section>
449 <title>Mounting</title>
450 <body>
452 <p>
453 Now that your partitions are initialized and are housing a filesystem, it is
454 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
455 create the necessary mount directories for every partition you created. As an
456 example we create a mount-point and mount the root and boot partition:
457 </p>
459 <pre caption="Mounting partitions">
460 # <i>mkdir /mnt/gentoo</i>
461 # <i>mount /dev/hda3 /mnt/gentoo</i>
462 </pre>
464 <note>
465 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
466 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
467 also holds for <path>/var/tmp</path>.
468 </note>
470 <p>
471 Finally we have to create the <path>/dev</path> files in our new home, which is
472 needed during the bootloader installation. This could be done by "bind"-mapping
473 the <path>/dev</path>-filesystem from the LiveCD:
474 </p>
476 <pre caption="Bind-mounting the /dev-filesystem">
477 # <i>mkdir /mnt/gentoo/dev</i>
478 # <i>mount -o bind /dev /mnt/gentoo/dev</i>
479 </pre>
481 <p>
482 We will also have to mount the proc filesystem (a virtual interface with the
483 kernel) on <path>/proc</path>. But first we will need to place our files on the partitions.
484 </p>
486 <p>
487 Continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
488 Installation Files</uri>.
489 </p>
491 </body>
492 </section>
493 </sections>

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