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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 1.9 2004/07/16 09:37:11 neysx 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 (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 (Pegasos) to Partition your Disk</title>
221 <body>
223 <p>
224 To begin let's fire up <c>parted</c>:
225 </p>
227 <pre caption="Starting parted">
228 # <i>parted /dev/hda</i>
229 </pre>
231 <p>
232 If the drive is unpartitioned, run <c>mklabel amiga</c> to create a new
233 disklabel for the drive.
234 </p>
236 <p>
237 You can type <c>print</c> at any time in parted to display the current partition
238 table. Your changes aren't saved until you quit the application; if at any time
239 you change your mind or made a mistake you can press <c>Ctrl-c</c> to abort
240 parted.
241 </p>
243 <p>
244 If you intend to also install MorphOS on your Pegasos create an affs1 filesystem
245 named "BI0" (BI zero) at the start of the drive. 50MB should be more than enough
246 to store the MorphOS kernel. If you have a Pegasos I or intend to use reiserfs,
247 xfs or jfs you will also have to store your Linux kernel on this partition (the
248 Pegasos II can boot from ext2/ext3 drives). To create the partition run
249 <c>mkpart primary affs1 START END</c> where <c>START</c> and <c>END</c> should
250 be replaced with the megabyte range (f.i. <c>5 55</c> creates a 50 MB partition
251 starting at 5MB and ending at 55MB.
252 </p>
254 <p>
255 You need to create two partitions for Linux, one root filesystem for all your
256 program files etc, and one swap partition. To create the root filesystem you
257 must first decide which filesystem to use. Possible options are ext2, ext3,
258 reiserfs, jfs and xfs. Unless you know what you are doing, use ext3. Run
259 <c>mkpart primary ext3 START END</c> to create an ext3 partition. Again, replace
260 <c>START</c> and <c>END</c> with the megabyte start and stop marks for the
261 partition.
262 </p>
264 <p>
265 It is generally recommended that you create a swap partition the same size as
266 the amount of RAM in your computer times two. You will probably get away with a
267 smaller swap partition unless you intend to run a lot of applications at the
268 same time (although at least 512MB is recommended). To create the swap
269 partition, run <c>mkpart primary linux-swap START END</c>.
270 </p>
272 <p>
273 Write down the partition minor numbers as they are required during the
274 installation process. To dislay the minor numbers run <c>print</c>. Your drives
275 are accessed as <path>/dev/hdaX</path> where X is replaced with the minor number
276 of the partition.
277 </p>
279 <p>
280 When you are done in parted simply run <c>quit</c>.
281 </p>
283 </body>
284 </section>
285 <section id="filesystems">
286 <title>Creating Filesystems</title>
287 <subsection>
288 <title>Introduction</title>
289 <body>
291 <p>
292 Now that your partitions are created, it is time to place a filesystem on them.
293 If you don't care about what filesystem to choose and are happy with what we use
294 as default in this handbook, continue with <uri
295 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
296 Otherwise read on to learn about the available filesystems...
297 </p>
299 </body>
300 </subsection>
301 <subsection>
302 <title>Filesystems?</title>
303 <body>
305 <p>
306 Several filesystems are available. Ext2 and ext3 are found stable on the
307 PPC architecture, reiserfs and xfs are in experimental stage. jfs is
308 unsupported.
309 </p>
311 <p>
312 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
313 journaling, which means that routine ext2 filesystem checks at startup time can
314 be quite time-consuming. There is now quite a selection of newer-generation
315 journaled filesystems that can be checked for consistency very quickly and are
316 thus generally preferred over their non-journaled counterparts. Journaled
317 filesystems prevent long delays when you boot your system and your filesystem
318 happens to be in an inconsistent state.
319 </p>
321 <p>
322 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
323 journaling for fast recovery in addition to other enhanced journaling modes like
324 full data and ordered data journaling. ext3 is a very good and reliable
325 filesystem. It has an additional hashed b-tree indexing option that enables
326 high performance in almost all situations. In short, ext3 is an excellent
327 filesystem.
328 </p>
330 <p>
331 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
332 performance and greatly outperforms both ext2 and ext3 when dealing with small
333 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
334 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
335 solid and usable as both general-purpose filesystem and for extreme cases such
336 as the creation of large filesystems, the use of many small files, very large
337 files and directories containing tens of thousands of files.
338 </p>
340 <p>
341 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
342 feature-set and is optimized for scalability. We only recommend using this
343 filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
344 an uninterruptible power supply. Because XFS aggressively caches in-transit data
345 in RAM, improperly designed programs (those that don't take proper precautions
346 when writing files to disk and there are quite a few of them) can lose a good
347 deal of data if the system goes down unexpectedly.
348 </p>
350 <p>
351 <b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
352 become production-ready and there hasn't been a sufficient track record to
353 comment positively nor negatively on its general stability at this point.
354 </p>
356 </body>
357 </subsection>
358 <subsection id="filesystems-apply">
359 <title>Applying a Filesystem to a Partition</title>
360 <body>
362 <p>
363 To create a filesystem on a partition or volume, there are tools available for
364 each possible filesystem:
365 </p>
367 <table>
368 <tr>
369 <th>Filesystem</th>
370 <th>Creation Command</th>
371 </tr>
372 <tr>
373 <ti>ext2</ti>
374 <ti><c>mke2fs</c></ti>
375 </tr>
376 <tr>
377 <ti>ext3</ti>
378 <ti><c>mke2fs -j</c></ti>
379 </tr>
380 <tr>
381 <ti>reiserfs</ti>
382 <ti><c>mkreiserfs</c></ti>
383 </tr>
384 <tr>
385 <ti>xfs</ti>
386 <ti><c>mkfs.xfs</c></ti>
387 </tr>
388 <tr>
389 <ti>jfs</ti>
390 <ti><c>mkfs.jfs</c></ti>
391 </tr>
392 </table>
394 <p>
395 For instance, to have the root partition (<path>/dev/hda3</path> in our example)
396 in ext3 (as in our example), you would use:
397 </p>
399 <pre caption="Applying a filesystem on a partition">
400 # <i>mke2fs -j /dev/hda3</i>
401 </pre>
403 <p>
404 Now create the filesystems on your newly created partitions (or logical
405 volumes).
406 </p>
408 </body>
409 </subsection>
410 <subsection>
411 <title>Activating the Swap Partition</title>
412 <body>
414 <p>
415 <c>mkswap</c> is the command that is used to initialize swap partitions:
416 </p>
418 <pre caption="Creating a Swap signature">
419 # <i>mkswap /dev/hda2</i>
420 </pre>
422 <p>
423 To activate the swap partition, use <c>swapon</c>:
424 </p>
426 <pre caption="Activating the swap partition">
427 # <i>swapon /dev/hda2</i>
428 </pre>
430 <p>
431 Create and activate the swap now.
432 </p>
434 </body>
435 </subsection>
436 </section>
437 <section>
438 <title>Mounting</title>
439 <body>
441 <p>
442 Now that your partitions are initialized and are housing a filesystem, it is
443 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
444 create the necessary mount directories for every partition you created. As an
445 example we create a mount-point and mount the root and boot partition:
446 </p>
448 <pre caption="Mounting partitions">
449 # <i>mkdir /mnt/gentoo</i>
450 # <i>mount /dev/hda3 /mnt/gentoo</i>
451 </pre>
453 <note>
454 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
455 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
456 also holds for <path>/var/tmp</path>.
457 </note>
459 <p>
460 We also need to mount the proc filesystem (a virtual interface with the kernel)
461 on <path>/proc</path>. We first create the <path>/mnt/gentoo/proc</path>
462 mountpoint and then mount the filesystem:
463 </p>
465 <pre caption="Creating the /mnt/gentoo/proc mountpoint">
466 # <i>mkdir /mnt/gentoo/proc</i>
467 # <i>mount -t proc none /mnt/gentoo/proc</i>
468 </pre>
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 Now continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
483 Installation Files</uri>.
484 </p>
486 </body>
487 </section>
488 </sections>

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