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initial import of arm handbook

1 <?xml version='1.0' encoding='UTF-8'?>
2 <!DOCTYPE sections SYSTEM "/dtd/book.dtd">
3
4 <!-- The content of this document is licensed under the CC-BY-SA license -->
5 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
6
7 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/handbook/hb-install-x86+amd64-disk.xml,v 1.3 2006/08/30 22:52:28 nightmorph Exp $ -->
8
9 <sections>
10
11 <version>4.0</version>
12 <date>2006-08-30</date>
13
14 <section>
15 <title>Introduction to Block Devices</title>
16 <subsection>
17 <title>Block Devices</title>
18 <body>
19
20 <p>
21 We'll take a good look at disk-oriented aspects of Gentoo Linux
22 and Linux in general, including Linux filesystems, partitions and block devices.
23 Then, once you're familiar with the ins and outs of disks and filesystems,
24 you'll be guided through the process of setting up partitions and filesystems
25 for your Gentoo Linux installation.
26 </p>
27
28 <p>
29 To begin, we'll introduce <e>block devices</e>. The most famous block device is
30 probably the one that represents the first IDE drive in a Linux system, namely
31 <path>/dev/hda</path>. If your system uses SCSI or SATA drives, then your
32 first hard drive would be <path>/dev/sda</path>.
33 </p>
34
35 <p>
36 The block devices above represent an abstract interface to the disk. User
37 programs can use these block devices to interact with your disk without worrying
38 about whether your drives are IDE, SCSI or something else. The program can
39 simply address the storage on the disk as a bunch of contiguous,
40 randomly-accessible 512-byte blocks.
41 </p>
42
43 </body>
44 </subsection>
45 <subsection>
46 <title>Partitions</title>
47 <body>
48
49 <p>
50 Although it is theoretically possible to use a full disk to house your Linux
51 system, this is almost never done in practice. Instead, full disk block devices
52 are split up in smaller, more manageable block devices. On <keyval id="arch"/>
53 systems, these are called <e>partitions</e>.
54 </p>
55
56 <p>
57 Partitions are divided in three types:
58 <e>primary</e>, <e>extended</e> and <e>logical</e>.
59 </p>
60
61 <p>
62 A <e>primary</e> partition is a partition which has its information stored in
63 the MBR (master boot record). As an MBR is very small (512 bytes) only four
64 primary partitions can be defined (for instance, <path>/dev/hda1</path> to
65 <path>/dev/hda4</path>).
66 </p>
67
68 <p>
69 An <e>extended</e> partition is a special primary partition (meaning the
70 extended partition must be one of the four possible primary partitions) which
71 contains more partitions. Such a partition didn't exist originally, but as
72 four partitions were too few, it was brought to life to extend the formatting
73 scheme without losing backward compatibility.
74 </p>
75
76 <p>
77 A <e>logical</e> partition is a partition inside the extended partition. Their
78 definitions aren't placed inside the MBR, but are declared inside the extended
79 partition.
80 </p>
81
82 </body>
83 </subsection>
84 </section>
85 <section>
86 <title>Designing a Partitioning Scheme</title>
87 <subsection>
88 <title>Default Partitioning Scheme</title>
89 <body>
90
91 <warn>
92 The NetWinder firmware, NeTTrom, can only read ext2 partitions realiably so you
93 must have a separate ext2 boot partition.
94 </warn>
95
96 <p>
97 If you are not interested in drawing up a partitioning scheme for your system,
98 you can use the partitioning scheme we use throughout this book:
99 </p>
100
101 <table>
102 <tr>
103 <th>Partition</th>
104 <th>Filesystem</th>
105 <th>Size</th>
106 <th>Description</th>
107 </tr>
108 <tr>
109 <ti><path>/dev/hda1</path></ti>
110 <ti>ext2</ti>
111 <ti>32M</ti>
112 <ti>Boot partition</ti>
113 </tr>
114 <tr>
115 <ti><path>/dev/hda2</path></ti>
116 <ti>(swap)</ti>
117 <ti>512M</ti>
118 <ti>Swap partition</ti>
119 </tr>
120 <tr>
121 <ti><path>/dev/hda3</path></ti>
122 <ti>ext3</ti>
123 <ti>Rest of the disk</ti>
124 <ti>Root partition</ti>
125 </tr>
126 </table>
127
128 <p>
129 If you are interested in knowing how big a partition should be, or even how
130 many partitions you need, read on. Otherwise continue now with partitioning
131 your disk by reading <uri link="#fdisk">Using fdisk to Partition your
132 Disk</uri>.
133 </p>
134
135 </body>
136 </subsection>
137 <subsection>
138 <title>How Many and How Big?</title>
139 <body>
140
141 <p>
142 The number of partitions is highly dependent on your environment. For instance,
143 if you have lots of users, you will most likely want to have your
144 <path>/home</path> separate as it increases security and makes backups easier.
145 If you are installing Gentoo to perform as a mailserver, your
146 <path>/var</path> should be separate as all mails are stored inside
147 <path>/var</path>. A good choice of filesystem will then maximise your
148 performance. Gameservers will have a separate <path>/opt</path> as most gaming
149 servers are installed there. The reason is similar for <path>/home</path>:
150 security and backups. You will definitely want to keep <path>/usr</path> big:
151 not only will it contain the majority of applications, the Portage tree alone
152 takes around 500 Mbyte excluding the various sources that are stored in it.
153 </p>
154
155 <p>
156 As you can see, it very much depends on what you want to achieve. Separate
157 partitions or volumes have the following advantages:
158 </p>
159
160 <ul>
161 <li>
162 You can choose the best performing filesystem for each partition or volume
163 </li>
164 <li>
165 Your entire system cannot run out of free space if one defunct tool is
166 continuously writing files to a partition or volume
167 </li>
168 <li>
169 If necessary, file system checks are reduced in time, as multiple checks can
170 be done in parallel (although this advantage is more with multiple disks than
171 it is with multiple partitions)
172 </li>
173 <li>
174 Security can be enhanced by mounting some partitions or volumes read-only,
175 nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
176 </li>
177 </ul>
178
179 <p>
180 However, multiple partitions have one big disadvantage: if not configured
181 properly, you might result in having a system with lots of free space on one
182 partition and none on another. There is also a 15-partition limit for SCSI and
183 SATA.
184 </p>
185
186 <p>
187 As an example partitioning, we show you one for a 20GB disk, used as a
188 demonstration laptop (containing webserver, mailserver, gnome, ...):
189 </p>
190
191 <pre caption="Filesystem usage example">
192 $ <i>df -h</i>
193 Filesystem Type Size Used Avail Use% Mounted on
194 /dev/hda5 ext3 509M 132M 351M 28% /
195 /dev/hda2 ext3 5.0G 3.0G 1.8G 63% /home
196 /dev/hda7 ext3 7.9G 6.2G 1.3G 83% /usr
197 /dev/hda8 ext3 1011M 483M 477M 51% /opt
198 /dev/hda9 ext3 2.0G 607M 1.3G 32% /var
199 /dev/hda1 ext2 51M 17M 31M 36% /boot
200 /dev/hda6 swap 516M 12M 504M 2% &lt;not mounted&gt;
201 <comment>(Unpartitioned space for future usage: 2 GB)</comment>
202 </pre>
203
204 <p>
205 <path>/usr</path> is rather full (83% used) here, but once
206 all software is installed, <path>/usr</path> doesn't tend to grow that much.
207 Although allocating a few gigabytes of disk space for <path>/var</path> may
208 seem excessive, remember that Portage uses this partition by default for
209 compiling packages. If you want to keep <path>/var</path> at a more reasonable
210 size, such as 1GB, you will need to alter your <c>PORTAGE_TMPDIR</c> variable
211 in <path>/etc/make.conf</path> to point to the partition with enough free space
212 for compiling extremely large packages such as OpenOffice.
213 </p>
214
215 </body>
216 </subsection>
217 </section>
218 <section id="fdisk">
219 <title>Using fdisk to Partition your Disk</title>
220 <subsection>
221 <body>
222
223 <p>
224 The following parts explain how to create the example partition layout
225 described previously, namely:
226 </p>
227
228 <table>
229 <tr>
230 <th>Partition</th>
231 <th>Description</th>
232 </tr>
233 <tr>
234 <ti><path>/dev/hda1</path></ti>
235 <ti>Boot partition</ti>
236 </tr>
237 <tr>
238 <ti><path>/dev/hda2</path></ti>
239 <ti>Swap partition</ti>
240 </tr>
241 <tr>
242 <ti><path>/dev/hda3</path></ti>
243 <ti>Root partition</ti>
244 </tr>
245 </table>
246
247 <p>
248 Change your partition layout according to your own preference.
249 </p>
250
251 </body>
252 </subsection>
253 <subsection>
254 <title>Viewing the Current Partition Layout</title>
255 <body>
256
257 <p>
258 <c>fdisk</c> is a popular and powerful tool to split your disk into partitions.
259 Fire up <c>fdisk</c> on your disk (in our example, we use
260 <path>/dev/hda</path>):
261 </p>
262
263 <pre caption="Starting fdisk">
264 # <i>fdisk /dev/hda</i>
265 </pre>
266
267 <p>
268 Once in <c>fdisk</c>, you'll be greeted with a prompt that looks like this:
269 </p>
270
271 <pre caption="fdisk prompt">
272 Command (m for help):
273 </pre>
274
275 <p>
276 Type <c>p</c> to display your disk's current partition configuration:
277 </p>
278
279 <pre caption="An example partition configuration">
280 Command (m for help): <i>p</i>
281
282 Disk /dev/hda: 240 heads, 63 sectors, 2184 cylinders
283 Units = cylinders of 15120 * 512 bytes
284
285 Device Boot Start End Blocks Id System
286 /dev/hda1 1 14 105808+ 83 Linux
287 /dev/hda2 15 49 264600 82 Linux swap
288 /dev/hda3 50 70 158760 83 Linux
289 /dev/hda4 71 2184 15981840 5 Extended
290 /dev/hda5 71 209 1050808+ 83 Linux
291 /dev/hda6 210 348 1050808+ 83 Linux
292 /dev/hda7 349 626 2101648+ 83 Linux
293 /dev/hda8 627 904 2101648+ 83 Linux
294 /dev/hda9 905 2184 9676768+ 83 Linux
295
296 Command (m for help):
297 </pre>
298
299 <p>
300 This particular disk is configured to house seven Linux filesystems (each with
301 a corresponding partition listed as "Linux") as well as a swap partition
302 (listed as "Linux swap").
303 </p>
304
305 </body>
306 </subsection>
307 <subsection>
308 <title>Removing all Partitions</title>
309 <body>
310
311 <p>
312 We will first remove all existing partitions from the disk. Type <c>d</c> to
313 delete a partition. For instance, to delete an existing <path>/dev/hda1</path>:
314 </p>
315
316 <pre caption="Deleting a partition">
317 Command (m for help): <i>d</i>
318 Partition number (1-4): <i>1</i>
319 </pre>
320
321 <p>
322 The partition has been scheduled for deletion. It will no longer show up if you
323 type <c>p</c>, but it will not be erased until your changes have been saved. If
324 you made a mistake and want to abort without saving your changes, type <c>q</c>
325 immediately and hit enter and your partition will not be deleted.
326 </p>
327
328 <p>
329 Now, assuming that you do indeed want to wipe out all the partitions on your
330 system, repeatedly type <c>p</c> to print out a partition listing and then type
331 <c>d</c> and the number of the partition to delete it. Eventually, you'll end
332 up with a partition table with nothing in it:
333 </p>
334
335 <pre caption="An empty partition table">
336 Disk /dev/hda: 30.0 GB, 30005821440 bytes
337 240 heads, 63 sectors/track, 3876 cylinders
338 Units = cylinders of 15120 * 512 = 7741440 bytes
339
340 Device Boot Start End Blocks Id System
341
342 Command (m for help):
343 </pre>
344
345 <p>
346 Now that the in-memory partition table is empty, we're ready to create the
347 partitions. We will use a default partitioning scheme as discussed previously.
348 Of course, don't follow these instructions to the letter if you don't want the
349 same partitioning scheme!
350 </p>
351
352 </body>
353 </subsection>
354 <subsection>
355 <title>Creating the Boot Partition</title>
356 <body>
357
358 <p>
359 We first create a small boot partition. Type <c>n</c> to create a new partition,
360 then <c>p</c> to select a primary partition, followed by <c>1</c> to select the
361 first primary partition. When prompted for the first cylinder, hit enter. When
362 prompted for the last cylinder, type <c>+32M</c> to create a partition 32 Mbyte
363 in size:
364 </p>
365
366 <pre caption="Creating the boot partition">
367 Command (m for help): <i>n</i>
368 Command action
369 e extended
370 p primary partition (1-4)
371 <i>p</i>
372 Partition number (1-4): <i>1</i>
373 First cylinder (1-3876, default 1): <comment>(Hit Enter)</comment>
374 Using default value 1
375 Last cylinder or +size or +sizeM or +sizeK (1-3876, default 3876): <i>+32M</i>
376 </pre>
377
378 <p>
379 Now, when you type <c>p</c>, you should see the following partition printout:
380 </p>
381
382 <pre caption="Created boot partition">
383 Command (m for help): <i>p</i>
384
385 Disk /dev/hda: 30.0 GB, 30005821440 bytes
386 240 heads, 63 sectors/track, 3876 cylinders
387 Units = cylinders of 15120 * 512 = 7741440 bytes
388
389 Device Boot Start End Blocks Id System
390 /dev/hda1 1 14 105808+ 83 Linux
391 </pre>
392
393 <p>
394 We need to make this partition bootable. Type <c>a</c> to toggle the bootable
395 flag on a partition and select <c>1</c>. If you press <c>p</c> again, you will
396 notice that an <path>*</path> is placed in the "Boot" column.
397 </p>
398
399 </body>
400 </subsection>
401 <subsection>
402 <title>Creating the Swap Partition</title>
403 <body>
404
405 <p>
406 Let's now create the swap partition. To do this, type <c>n</c> to create a new
407 partition, then <c>p</c> to tell fdisk that you want a primary partition. Then
408 type <c>2</c> to create the second primary partition, <path>/dev/hda2</path> in
409 our case. When prompted for the first cylinder, hit enter. When prompted for
410 the last cylinder, type <c>+512M</c> to create a partition 512MB in size. After
411 you've done this, type <c>t</c> to set the partition type, <c>2</c> to select
412 the partition you just created and then type in <c>82</c> to set the partition
413 type to "Linux Swap". After completing these steps, typing <c>p</c> should
414 display a partition table that looks similar to this:
415 </p>
416
417 <pre caption="Partition listing after creating a swap partition">
418 Command (m for help): <i>p</i>
419
420 Disk /dev/hda: 30.0 GB, 30005821440 bytes
421 240 heads, 63 sectors/track, 3876 cylinders
422 Units = cylinders of 15120 * 512 = 7741440 bytes
423
424 Device Boot Start End Blocks Id System
425 /dev/hda1 * 1 14 105808+ 83 Linux
426 /dev/hda2 15 81 506520 82 Linux swap
427 </pre>
428
429 </body>
430 </subsection>
431 <subsection>
432 <title>Creating the Root Partition</title>
433 <body>
434
435 <p>
436 Finally, let's create the root partition. To do this, type <c>n</c> to create a
437 new partition, then <c>p</c> to tell fdisk that you want a primary partition.
438 Then type <c>3</c> to create the third primary partition, <path>/dev/hda3</path>
439 in our case. When prompted for the first cylinder, hit enter. When prompted for
440 the last cylinder, hit enter to create a partition that takes up the rest of the
441 remaining space on your disk. After completing these steps, typing <c>p</c>
442 should display a partition table that looks similar to this:
443 </p>
444
445 <pre caption="Partition listing after creating the root partition">
446 Command (m for help): <i>p</i>
447
448 Disk /dev/hda: 30.0 GB, 30005821440 bytes
449 240 heads, 63 sectors/track, 3876 cylinders
450 Units = cylinders of 15120 * 512 = 7741440 bytes
451
452 Device Boot Start End Blocks Id System
453 /dev/hda1 * 1 14 105808+ 83 Linux
454 /dev/hda2 15 81 506520 82 Linux swap
455 /dev/hda3 82 3876 28690200 83 Linux
456 </pre>
457
458 </body>
459 </subsection>
460 <subsection>
461 <title>Saving the Partition Layout</title>
462 <body>
463
464 <p>
465 To save the partition layout and exit <c>fdisk</c>, type <c>w</c>.
466 </p>
467
468 <pre caption="Save and exit fdisk">
469 Command (m for help): <i>w</i>
470 </pre>
471
472 <p>
473 Now that your partitions are created, you can now continue with <uri
474 link="#filesystems">Creating Filesystems</uri>.
475 </p>
476
477 </body>
478 </subsection>
479 </section>
480 <section id="filesystems">
481 <title>Creating Filesystems</title>
482 <subsection>
483 <title>Introduction</title>
484 <body>
485
486 <p>
487 Now that your partitions are created, it is time to place a filesystem on them.
488 If you don't care about what filesystem to choose and are happy with what we use
489 as default in this handbook, continue with <uri
490 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
491 Otherwise read on to learn about the available filesystems...
492 </p>
493
494 </body>
495 </subsection>
496 <subsection>
497 <title>Filesystems?</title>
498 <body>
499
500 <p>
501 Several filesystems are available. Some of them are found stable on the amd64
502 architecture, others aren't. The following filesystems are found to be stable:
503 ext2 and ext3. jfs and reiserfs may work but need more testing. If you're
504 really adventurous you can try the unsupported filesystems.
505 </p>
506
507 <p>
508 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
509 journaling, which means that routine ext2 filesystem checks at startup time can
510 be quite time-consuming. There is now quite a selection of newer-generation
511 journaled filesystems that can be checked for consistency very quickly and are
512 thus generally preferred over their non-journaled counterparts. Journaled
513 filesystems prevent long delays when you boot your system and your filesystem
514 happens to be in an inconsistent state.
515 </p>
516
517 <p>
518 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
519 journaling for fast recovery in addition to other enhanced journaling modes like
520 full data and ordered data journaling. ext3 is a very good and reliable
521 filesystem.
522 </p>
523
524 <p>
525 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
526 performance and greatly outperforms both ext2 and ext3 when dealing with small
527 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
528 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
529 solid and usable as both general-purpose filesystem and for extreme cases such
530 as the creation of large filesystems, the use of many small files, very large
531 files and directories containing tens of thousands of files.
532 </p>
533
534 <p>
535 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
536 feature-set and is optimized for scalability. We only recommend using this
537 filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
538 an uninterruptible power supply. Because XFS aggressively caches in-transit data
539 in RAM, improperly designed programs (those that don't take proper precautions
540 when writing files to disk and there are quite a few of them) can lose a good
541 deal of data if the system goes down unexpectedly.
542 </p>
543
544 <p>
545 <b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
546 become production-ready and there hasn't been a sufficient track record to
547 comment positively nor negatively on its general stability at this point.
548 </p>
549
550 </body>
551 </subsection>
552 <subsection id="filesystems-apply">
553 <title>Applying a Filesystem to a Partition</title>
554 <body>
555
556 <p>
557 To create a filesystem on a partition or volume, there are tools available for
558 each possible filesystem:
559 </p>
560
561 <table>
562 <tr>
563 <th>Filesystem</th>
564 <th>Creation Command</th>
565 </tr>
566 <tr>
567 <ti>ext2</ti>
568 <ti><c>mke2fs</c></ti>
569 </tr>
570 <tr>
571 <ti>ext3</ti>
572 <ti><c>mke2fs -j</c></ti>
573 </tr>
574 <tr>
575 <ti>reiserfs</ti>
576 <ti><c>mkreiserfs</c></ti>
577 </tr>
578 <tr>
579 <ti>xfs</ti>
580 <ti><c>mkfs.xfs</c></ti>
581 </tr>
582 <tr>
583 <ti>jfs</ti>
584 <ti><c>mkfs.jfs</c></ti>
585 </tr>
586 </table>
587
588 <p>
589 For instance, to have the boot partition (<path>/dev/hda1</path> in our
590 example) in ext2 and the root partition (<path>/dev/hda3</path> in our example)
591 in ext3 (as in our example), you would use:
592 </p>
593
594 <pre caption="Applying a filesystem on a partition">
595 # <i>mke2fs /dev/hda1</i>
596 # <i>mke2fs -j /dev/hda3</i>
597 </pre>
598
599 <p>
600 Now create the filesystems on your newly created partitions (or logical
601 volumes).
602 </p>
603
604 </body>
605 </subsection>
606 <subsection>
607 <title>Activating the Swap Partition</title>
608 <body>
609
610 <p>
611 <c>mkswap</c> is the command that is used to initialize swap partitions:
612 </p>
613
614 <pre caption="Creating a Swap signature">
615 # <i>mkswap /dev/hda2</i>
616 </pre>
617
618 <p>
619 To activate the swap partition, use <c>swapon</c>:
620 </p>
621
622 <pre caption="Activating the swap partition">
623 # <i>swapon /dev/hda2</i>
624 </pre>
625
626 <p>
627 Create and activate the swap with the commands mentioned above.
628 </p>
629
630 </body>
631 </subsection>
632 </section>
633 <section>
634 <title>Mounting</title>
635 <body>
636
637 <p>
638 Now that your partitions are initialized and are housing a filesystem, it is
639 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
640 create the necessary mount directories for every partition you created. As an
641 example we mount the root and boot partition:
642 </p>
643
644 <pre caption="Mounting partitions">
645 # <i>mount /dev/hda3 /mnt/gentoo</i>
646 # <i>mkdir /mnt/gentoo/boot</i>
647 # <i>mount /dev/hda1 /mnt/gentoo/boot</i>
648 </pre>
649
650 <note>
651 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
652 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
653 also holds for <path>/var/tmp</path>.
654 </note>
655
656 <p>
657 We will also have to mount the proc filesystem (a virtual interface with the
658 kernel) on <path>/proc</path>. But first we will need to place our files on the partitions.
659 </p>
660
661 <p>
662 Continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
663 Installation Files</uri>.
664 </p>
665
666 </body>
667 </section>
668 </sections>

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