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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-hppa-disk.xml,v 1.15 2005/02/20 12:38:07 swift Exp $ -->
8
9 <sections>
10
11 <version>1.11</version>
12 <date>2005-06-10</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 SCSI HD in a Linux system, namely
31 <path>/dev/sda</path>.
32 </p>
33
34 <p>
35 The block devices above represent an abstract interface to the disk. User
36 programs can use these block devices to interact with your disk without worrying
37 about whether your drives are IDE, SCSI or something else. The program can
38 simply address the storage on the disk as a bunch of contiguous,
39 randomly-accessible 512-byte blocks.
40 </p>
41
42 </body>
43 </subsection>
44 <subsection>
45 <title>Partitions and Slices</title>
46 <body>
47
48 <p>
49 Although it is theoretically possible to use a full disk to house your Linux
50 system, this is almost never done in practice. Instead, full disk block devices
51 are split up in smaller, more manageable block devices. On most systems,
52 these are called <e>partitions</e>. Other architectures use a similar technique,
53 called <e>slices</e>.
54 </p>
55
56 </body>
57 </subsection>
58 </section>
59 <section>
60 <title>Designing a Partitioning Scheme</title>
61 <subsection>
62 <title>How Many and How Big?</title>
63 <body>
64
65 <p>
66 The number of partitions is highly dependent on your environment. For instance,
67 if you have lots of users, you will most likely want to have your
68 <path>/home</path> separate as it increases security and makes backups easier.
69 If you are installing Gentoo to perform as a mailserver, your
70 <path>/var</path> should be separate as all mails are stored inside
71 <path>/var</path>. A good choice of filesystem will then maximise your
72 performance. Gameservers will have a separate <path>/opt</path> as most gaming
73 servers are installed there. The reason is similar for <path>/home</path>:
74 security and backups. You will definitely want to keep <path>/usr</path> big:
75 not only will it contain the majority of applications, the Portage tree alone
76 takes around 500 Mbyte excluding the various sources that are stored in it.
77
78 </p>
79
80 <p>
81 As you can see, it very much depends on what you want to achieve. Separate
82 partitions or volumes have the following advantages:
83 </p>
84
85 <ul>
86 <li>
87 You can choose the best performing filesystem for each partition or volume
88 </li>
89 <li>
90 Your entire system cannot run out of free space if one defunct tool is
91 continuously writing files to a partition or volume
92 </li>
93 <li>
94 If necessary, file system checks are reduced in time, as multiple checks can
95 be done in parallel (although this advantage is more with multiple disks than
96 it is with multiple partitions)
97 </li>
98 <li>
99 Security can be enhanced by mounting some partitions or volumes read-only,
100 nosuid (setuid bits are ignored), noexec (executable bits are ignored) etc.
101 </li>
102 </ul>
103
104 <p>
105 However, multiple partitions have one big disadvantage: if not configured
106 properly, you might result in having a system with lots
107 of free space on one partition and none on another. There is also a 15-partition
108 limit for SCSI and SATA.
109 </p>
110
111 </body>
112 </subsection>
113 </section>
114 <section>
115 <title>Using fdisk on HPPA to Partition your Disk</title>
116 <body>
117
118 <p>
119 Use <c>fdisk</c> to create the partitions you want:
120 </p>
121
122 <pre caption="Partitioning the disk">
123 # <i>fdisk /dev/sda</i>
124 </pre>
125
126 <p>
127 HPPA machines use the PC standard DOS partition tables. To create a new
128 DOS partition table, simply use the <c>o</c> command.
129 </p>
130
131 <pre caption="Creating a DOS partition table">
132 # <i>fdisk /dev/sda</i>
133
134 Command (m for help): <i>o</i>
135 Building a new DOS disklabel.
136 </pre>
137
138 <p>
139 PALO (the HPPA bootloader) needs a special partition to work. You have
140 to create a partition of at least 16MB at the beginning of your disk.
141 The partition type must be of type <e>f0</e> (Linux/PA-RISC boot).
142 </p>
143
144 <impo>
145 If you ignore this and continue without a special PALO partition, your system
146 will stop loving you and fail to start. Also, if your disk is larger than 2GB,
147 make sure that the boot partition is in the first 2GB of your disk. PALO is
148 unable to read a kernel after the 2GB limit.
149 </impo>
150
151 <pre caption="A simple default partition schema">
152 # <i>cat /etc/fstab</i>
153 /dev/sda2 /boot ext3 noauto,noatime 1 1
154 /dev/sda3 none swap sw 0 0
155 /dev/sda4 / ext3 noatime 0 0
156
157 # <i>fdisk /dev/sda</i>
158
159 Command (m for help): <i>p</i>
160
161 Disk /dev/sda: 4294 MB, 4294816768 bytes
162 133 heads, 62 sectors/track, 1017 cylinders
163 Units = cylinders of 8246 * 512 = 4221952 bytes
164
165 Device Boot Start End Blocks Id System
166 /dev/sda1 1 8 32953 f0 Linux/PA-RISC boot
167 /dev/sda2 9 20 49476 83 Linux
168 /dev/sda3 21 70 206150 82 Linux swap
169 /dev/sda4 71 1017 3904481 83 Linux
170 </pre>
171
172 <p>
173 Now that your partitions are created, you can now continue with <uri
174 link="#filesystems">Creating Filesystems</uri>.
175 </p>
176
177 </body>
178 </section>
179 <section id="filesystems">
180 <title>Creating Filesystems</title>
181 <subsection>
182 <title>Introduction</title>
183 <body>
184
185 <p>
186 Now that your partitions are created, it is time to place a filesystem on them.
187 If you don't care about what filesystem to choose and are happy with what we use
188 as default in this handbook, continue with <uri
189 link="#filesystems-apply">Applying a Filesystem to a Partition</uri>.
190 Otherwise read on to learn about the available filesystems...
191 </p>
192
193 </body>
194 </subsection>
195 <subsection>
196 <title>Filesystems?</title>
197 <body>
198
199 <p>
200 Several filesystems are available. Ext2, ext3, XFS and reiserfs are found stable on
201 the HPPA architecture. The others are very experimental.
202 </p>
203
204 <p>
205 <b>ext2</b> is the tried and true Linux filesystem but doesn't have metadata
206 journaling, which means that routine ext2 filesystem checks at startup time can
207 be quite time-consuming. There is now quite a selection of newer-generation
208 journaled filesystems that can be checked for consistency very quickly and are
209 thus generally preferred over their non-journaled counterparts. Journaled
210 filesystems prevent long delays when you boot your system and your filesystem
211 happens to be in an inconsistent state.
212 </p>
213
214 <p>
215 <b>ext3</b> is the journaled version of the ext2 filesystem, providing metadata
216 journaling for fast recovery in addition to other enhanced journaling modes like
217 full data and ordered data journaling. ext3 is a very good and reliable
218 filesystem. It has an additional hashed b-tree indexing option that enables
219 high performance in almost all situations. In short, ext3 is an excellent
220 filesystem.
221 </p>
222
223 <p>
224 <b>ReiserFS</b> is a B*-tree based filesystem that has very good overall
225 performance and greatly outperforms both ext2 and ext3 when dealing with small
226 files (files less than 4k), often by a factor of 10x-15x. ReiserFS also scales
227 extremely well and has metadata journaling. As of kernel 2.4.18+, ReiserFS is
228 solid and usable as both general-purpose filesystem and for extreme cases such
229 as the creation of large filesystems, the use of many small files, very large
230 files and directories containing tens of thousands of files.
231 </p>
232
233 <p>
234 <b>XFS</b> is a filesystem with metadata journaling which comes with a robust
235 feature-set and is optimized for scalability. We only recommend using this
236 filesystem on Linux systems with high-end SCSI and/or fibre channel storage and
237 an uninterruptible power supply. Because XFS aggressively caches in-transit data
238 in RAM, improperly designed programs (those that don't take proper precautions
239 when writing files to disk and there are quite a few of them) can lose a good
240 deal of data if the system goes down unexpectedly.
241 </p>
242
243 <p>
244 <b>JFS</b> is IBM's high-performance journaling filesystem. It has recently
245 become production-ready and there hasn't been a sufficient track record to
246 comment positively nor negatively on its general stability at this point.
247 </p>
248
249 </body>
250 </subsection>
251 <subsection id="filesystems-apply">
252 <title>Applying a Filesystem to a Partition</title>
253 <body>
254
255 <p>
256 To create a filesystem on a partition or volume, there are tools available for
257 each possible filesystem:
258 </p>
259
260 <table>
261 <tr>
262 <th>Filesystem</th>
263 <th>Creation Command</th>
264 </tr>
265 <tr>
266 <ti>ext2</ti>
267 <ti><c>mke2fs</c></ti>
268 </tr>
269 <tr>
270 <ti>ext3</ti>
271 <ti><c>mke2fs -j</c></ti>
272 </tr>
273 <tr>
274 <ti>reiserfs</ti>
275 <ti><c>mkreiserfs</c></ti>
276 </tr>
277 <tr>
278 <ti>xfs</ti>
279 <ti><c>mkfs.xfs</c></ti>
280 </tr>
281 <tr>
282 <ti>jfs</ti>
283 <ti><c>mkfs.jfs</c></ti>
284 </tr>
285 </table>
286
287 <p>
288 For instance, to have the boot partition (<path>/dev/sda2</path> in our
289 example) in ext2 and the root partition (<path>/dev/sda4</path> in our example)
290 in ext3 (as in our example), you would use:
291 </p>
292
293 <pre caption="Applying a filesystem on a partition">
294 # <i>mke2fs /dev/sda2</i>
295 # <i>mke2fs -j /dev/sda4</i>
296 </pre>
297
298 <p>
299 Now create the filesystems on your newly created partitions (or logical
300 volumes).
301 </p>
302
303 </body>
304 </subsection>
305 <subsection>
306 <title>Activating the Swap Partition</title>
307 <body>
308
309 <p>
310 <c>mkswap</c> is the command that is used to initialize swap partitions:
311 </p>
312
313 <pre caption="Creating a Swap signature">
314 # <i>mkswap /dev/sda3</i>
315 </pre>
316
317 <p>
318 To activate the swap partition, use <c>swapon</c>:
319 </p>
320
321 <pre caption="Activating the swap partition">
322 # <i>swapon /dev/sda3</i>
323 </pre>
324
325 <p>
326 Create and activate the swap with the commands mentioned above.
327 </p>
328
329 </body>
330 </subsection>
331 </section>
332 <section>
333 <title>Mounting</title>
334 <body>
335
336 <p>
337 Now that your partitions are initialized and are housing a filesystem, it is
338 time to mount those partitions. Use the <c>mount</c> command. Don't forget to
339 create the necessary mount directories for every partition you created. As an
340 example we mount the root and boot partition:
341 </p>
342
343 <pre caption="Mounting partitions">
344 # <i>mount /dev/sda4 /mnt/gentoo</i>
345 # <i>mkdir /mnt/gentoo/boot</i>
346 # <i>mount /dev/sda2 /mnt/gentoo/boot</i>
347 </pre>
348
349 <note>
350 If you want your <path>/tmp</path> to reside on a separate partition, be sure to
351 change its permissions after mounting: <c>chmod 1777 /mnt/gentoo/tmp</c>. This
352 also holds for <path>/var/tmp</path>.
353 </note>
354
355 <p>
356 We will also have to mount the proc filesystem (a virtual interface with the
357 kernel) on <path>/proc</path>. But first we will need to place our files on the partitions.
358 </p>
359
360 <p>
361 Continue with <uri link="?part=1&amp;chap=5">Installing the Gentoo
362 Installation Files</uri>.
363 </p>
364
365 </body>
366 </section>
367 </sections>

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