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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: /home/cvsroot/gentoo/xml/htdocs/doc/en/handbook/draft/hb-install-ppc-disk.xml,v 1.3 2004/04/19 14:21:10 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>Filesystem</th>
72 <th>Size</th>
73 <th>Description</th>
74 </tr>
75 <tr>
76 <ti><path>/dev/hda1</path></ti>
77 <ti>(Not needed)</ti>
78 <ti>(bootstrap)</ti>
79 <ti>800k</ti>
80 <ti>Apple_Bootstrap</ti>
81 </tr>
82 <tr>
83 <ti><path>/dev/hda2</path></ti>
84 <ti><path>/dev/hda1</path></ti>
85 <ti>(swap)</ti>
86 <ti>512M</ti>
87 <ti>Swap partition</ti>
88 </tr>
89 <tr>
90 <ti><path>/dev/hda3</path></ti>
91 <ti><path>/dev/hda2</path></ti>
92 <ti>ext3</ti>
93 <ti>Rest of the disk</ti>
94 <ti>Root partition</ti>
95 </tr>
96 </table>
98 <p>
99 If you are interested in knowing how big a partition should be, or even how
100 many partitions you need, read on. Otherwise continue now with
101 <uri link="#fdisk">Default: Using mac-fdisk (Apple/IBM) to Partition your
102 Disk</uri> or <uri link="#parted">Alternative: Using parted (Pegasos) to
103 Partition your Disk</uri>.
104 </p>
106 </body>
107 </subsection>
108 <subsection>
109 <title>How Many and How Big?</title>
110 <body>
112 <p>
113 The number of partitions is highly dependent on your environment. For instance,
114 if you have lots of users, you will most likely want to have your
115 <path>/home</path> separate as it increases security and makes backups easier.
116 If you are installing Gentoo to perform as a mailserver, your
117 <path>/var</path> should be separate as all mails are stored inside
118 <path>/var</path>. A good choice of filesystem will then maximise your
119 performance. Gameservers will have a separate <path>/opt</path> as most gaming
120 servers are installed there. The reason is similar for <path>/home</path>:
121 security and backups.
122 </p>
124 <p>
125 As you can see, it very much depends on what you want to achieve. Separate
126 partitions or volumes have the following advantages:
127 </p>
129 <ul>
130 <li>
131 You can choose the most performant filesystem for each partition or volume
132 </li>
133 <li>
134 Your entire system cannot run out of free space if one defunct tool is
135 continuously writing files to a partition or volume
136 </li>
137 <li>
138 If necessary, file system checks are reduced in time, as multiple checks can
139 be done in parallel (although this advantage is more with multiple disks than
140 it is with multiple partitions)
141 </li>
142 <li>
143 Security can be enhanced by mounting some partitions or volumes read-only,
144 nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
145 </li>
146 </ul>
148 <p>
149 However, multiple partitions have one big disadvantage: if not configured
150 properly, you might result in having a system with lots
151 of free space on one partition and none on another.
152 </p>
154 </body>
155 </subsection>
156 </section>
157 <section id="fdisk">
158 <title>Default: Using mac-fdisk (Apple/IBM) Partition your Disk</title>
159 <body>
161 <p>
162 At this point, create your partitions using <c>mac-fdisk</c>:
163 </p>
165 <pre caption="Starting mac-fdisk">
166 # <i>mac-fdisk /dev/hda</i>
167 </pre>
169 <p>
170 First delete the partitions you have cleared previously to make room for your
171 Linux partitions. Use <c>d</c> in <c>mac-fdisk</c> to delete those partition(s).
172 It will ask for the partition number to delete.
173 </p>
175 <p>
176 Second, create an <e>Apple_Bootstrap</e> partition by using <c>b</c>. It will
177 ask for what block you want to start. Enter the number of your first free
178 partition, followed by a <c>p</c>. For instance this is <c>1p</c>.
179 </p>
181 <note>
182 This partition is <e>not</e> a "boot" partition. It is not used by Linux at all;
183 you don't have to place any filesystem on it and you should never mount it. PPC
184 users don't need a an extra partition for <path>/boot</path>.
185 </note>
187 <p>
188 Now create a swap partition by pressing <c>c</c>. Again <c>mac-fdisk</c> will
189 ask for what block you want to start this partition from. As we used <c>1</c>
190 before to create the Apple_Bootstrap partition, you now have to enter
191 <c>2p</c>. When you're asked for the size, enter <c>512M</c> (or whatever size
192 you want -- 512MB is recommended though). When asked for a name, enter <c>swap</c>
193 (mandatory).
194 </p>
196 <p>
197 To create the root partition, enter <c>c</c>, followed by <c>3p</c> to select
198 from what block the root partition should start. When asked for the size, enter
199 <c>3p</c> again. <c>mac-fdisk</c> will interpret this as "Use all available
200 space". When asked for the name, enter <c>root</c> (mandatory).
201 </p>
203 <p>
204 To finish up, write the partition to the disk using <c>w</c> and <c>q</c> to
205 quit <c>mac-fdisk</c>.
206 </p>
208 <p>
209 Now that your partitions are created, you can now continue with <uri
210 link="#filesystems">Creating Filesystems</uri>.
211 </p>
213 </body>
214 </section>
215 <section id="parted">
216 <title>Using parted (Pegasos) to Partition your Disk</title>
217 <body>
219 <p>
220 To begin let's fire up <c>parted</c>:
221 </p>
223 <pre caption="Starting parted">
224 # <i>parted /dev/hda</i>
225 </pre>
227 <p>
228 If the drive is unpartitioned, run <c>mklabel amiga</c> to create a new
229 disklabel for the drive.
230 </p>
232 <p>
233 You can type <c>print</c> at any time in parted to display the current partition
234 table. Your changes aren't saved until you quit the application; if at any time
235 you change your mind or made a mistake you can press <c>Ctrl-c</c> to abort
236 parted.
237 </p>
239 <p>
240 If you intend to also install MorphOS on your Pegasos create an affs1 filesystem
241 named "BI0" (BI zero) at the start of the drive. 50MB should be more than enough
242 to store the MorphOS kernel. If you have a Pegasos I or intend to use reiserfs,
243 xfs or jfs you will also have to store your Linux kernel on this partition (the
244 Pegasos II can boot from ext2/ext3 drives). To create the partition run
245 <c>mkpart primary affs1 START END</c> where <c>START</c> and <c>END</c> should
246 be replaced with the megabyte range (f.i. <c>5 55</c> creates a 50 MB partition
247 starting at 5MB and ending at 55MB.
248 </p>
250 <p>
251 You need to create two partitions for Linux, one root filesystem for all your
252 program files etc, and one swap partition. To create the root filesystem you
253 must first decide which filesystem to use. Possible options are ext2, ext3,
254 reiserfs, jfs and xfs. Unless you know what you are doing use ext3. Run
255 <c>mkpart primary ext3 START END</c> to create an ext3 partition. Again, replace
256 <c>START</c> and <c>END</c> with the megabyte start and stop marks for the
257 partition.
258 </p>
260 <p>
261 It is generally recommended that you create a swap partition the same size as
262 the amount of RAM in your computer times two. You will probably get away with a
263 smaller swap partition unless you intend to run a lot of applications at the
264 same time (although at least 512MB is recommended). To create the swap
265 partition, run <c>mkpart primary linux-swap START END</c>.
266 </p>
268 <p>
269 Write down the partition minor numbers as they are required during the
270 installation process. To dislay the minor numbers run <c>print</c>. Your drives
271 are accessed as <path>/dev/hdaX</path> where X is replaced with the minor number
272 of the partition.
273 </p>
275 <p>
276 When you are done in parted simply run <c>quit</c>.
277 </p>
279 </body>
280 </section>
281 <section id="filesystems">
282 <title>Creating Filesystems</title>
283 <subsection>
284 <title>Introduction</title>
285 <body>
287 <p>
288 Now that your partitions are created, it is time to place a filesystem on them.
289 If you don't care about what filesystem to choose and are happy with what we use
290 as default in this handbook, continue with <uri
291 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
292 Otherwise read on to learn about the available filesystems...
293 </p>
295 </body>
296 </subsection>
297 <subsection>
298 <title>Filesystems?</title>
299 <body>
301 <p>
302 Several filesystems are available. Ext2 and ext3 are found stable on the
303 PPC architecture, reiserfs and xfs are in experimental stage. jfs is
304 unsupported.
305 </p>
307 <p>
308 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
309 journaling, which means that routine ext2 filesystem checks at startup time can
310 be quite time-consuming. There is now quite a selection of newer-generation
311 journaled filesystems that can be checked for consistency very quickly and are
312 thus generally preferred over their non-journaled counterparts. Journaled
313 filesystems prevent long delays when you boot your system and your filesystem
314 happens to be in an inconsistent state.
315 </p>
317 <p>
318 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
319 journaling for fast recovery in addition to other enhanced journaling modes like
320 full data and ordered data journaling. ext3 is a very good and reliable
321 filesystem. It has an additional hashed b-tree indexing option that enables
322 high performance in almost all situations. In short, ext3 is an excellent
323 filesystem.
324 </p>
326 <p>
327 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
328 performance and greatly outperforms both ext2 and ext3 when dealing with small
329 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
330 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
331 solid and usable as both general-purpose filesystem and for extreme cases such
332 as the creation of large filesystems, the use of many small files, very large
333 files and directories containing tens of thousands of files.
334 </p>
336 <p>
337 <b>XFS</b> is a filesystem with metadata journaling that is fully supported
338 under Gentoo Linux's xfs-sources kernel. It comes with a robust feature-set and
339 is optimized for scalability. We only recommend using this filesystem on Linux
340 systems with high-end SCSI and/or fibre channel storage and a uninterruptible
341 power supply. Because XFS aggressively caches in-transit data in RAM, improperly
342 designed programs (those that don't take proper precautions when writing files
343 to disk and there are quite a few of them) can lose a good deal of data if the
344 system goes down unexpectedly.
345 </p>
347 <p>
348 <b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
349 become production-ready and there hasn't been a sufficient track record to
350 comment positively nor negatively on its general stability at this point.
351 </p>
353 </body>
354 </subsection>
355 <subsection id="filesystems-apply">
356 <title>Applying a Filesystem to a Partition</title>
357 <body>
359 <p>
360 To create a filesystem on a partition or volume, there are tools available for
361 each possible filesystem:
362 </p>
364 <table>
365 <tr>
366 <th>Filesystem</th>
367 <th>Creation Command</th>
368 </tr>
369 <tr>
370 <ti>ext2</ti>
371 <ti><c>mke2fs</c></ti>
372 </tr>
373 <tr>
374 <ti>ext3</ti>
375 <ti><c>mke2fs -j</c></ti>
376 </tr>
377 <tr>
378 <ti>reiserfs</ti>
379 <ti><c>mkreiserfs</c></ti>
380 </tr>
381 <tr>
382 <ti>xfs</ti>
383 <ti><c>mkfs.xfs</c></ti>
384 </tr>
385 <tr>
386 <ti>jfs</ti>
387 <ti><c>mkfs.jfs</c></ti>
388 </tr>
389 </table>
391 <p>
392 For instance, to have the root partition (<path>/dev/hda3</path> in our example)
393 in ext3 (as in our example), you would use:
394 </p>
396 <pre caption="Applying a filesystem on a partition">
397 # <i>mke2fs -j /dev/hda3</i>
398 </pre>
400 <p>
401 Now create the filesystems on your newly created partitions (or logical
402 volumes).
403 </p>
405 </body>
406 </subsection>
407 <subsection>
408 <title>Activating the Swap Partition</title>
409 <body>
411 <p>
412 <c>mkswap</c> is the command that is used to initialize swap partitions:
413 </p>
415 <pre caption="Creating a Swap signature">
416 # <i>mkswap /dev/hda2</i>
417 </pre>
419 <p>
420 To activate the swap partition, use <c>swapon</c>:
421 </p>
423 <pre caption="Activating the swap partition">
424 # <i>swapon /dev/hda2</i>
425 </pre>
427 <p>
428 Create and activate the swap now.
429 </p>
431 </body>
432 </subsection>
433 </section>
434 <section>
435 <title>Mounting</title>
436 <body>
438 <p>
439 Now that your partitions are initialized and are housing a filesystem, it is
440 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
441 create the necessary mount directories for every partition you created. As an
442 example we create a mount-point and mount the root and boot partition:
443 </p>
445 <pre caption="Mounting partitions">
446 # <i>mkdir /mnt/gentoo</i>
447 # <i>mount /dev/hda3 /mnt/gentoo</i>
448 </pre>
450 <note>
451 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
452 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
453 also holds for <path>/var/tmp</path>.
454 </note>
456 <p>
457 We also need to mount the proc filesystem (a virtual interface with the kernel)
458 on <path>/proc</path>. We first create the <path>/mnt/gentoo/proc</path>
459 mountpoint and then mount the filesystem:
460 </p>
462 <pre caption="Creating the /mnt/gentoo/proc mountpoint">
463 # <i>mkdir /mnt/gentoo/proc</i>
464 # <i>mount -t proc none /mnt/gentoo/proc</i>
465 </pre>
467 <p>
468 Finally we have to create the <path>/dev</path> files in our new home, which is
469 needed during the bootloader installation. This could be done by "bind"-mapping
470 the <path>/dev</path>-filesystem from the LiveCD:
471 </p>
473 <pre caption="Bind-mounting the /dev-filesystem">
474 # <i>mkdir /mnt/gentoo/dev</i>
475 # <i>mount -o bind /dev /mnt/gentoo/dev</i>
476 </pre>
478 <p>
479 Now continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
480 Installation Files</uri>.
481 </p>
483 </body>
484 </section>
485 </sections>

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