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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/lvm2.xml,v 1.4 2004/07/04 16:32:03 swift Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4
5 <guide link = "/doc/en/lvm2.xml">
6 <title>Gentoo LVM2 installation</title>
7 <author title="Author">
8 <mail link="avi@CFFtechnologies.com">Avi Schwartz</mail>
9 </author>
10 <author title="Contributor">
11 <mail link="rajiv@gentoo.org">Rajiv Manglani</mail>
12 </author>
13 <author title="Editor">
14 <mail link="neysx@gentoo.org">Xavier Neys</mail>
15 </author>
16
17 <abstract>
18 This guide describes how to setup your Gentoo machine using the Logical Volume
19 Manager version 2 (LVM2).
20 </abstract>
21
22 <license/>
23
24 <version>2.0.2</version>
25 <date>July 04, 2004</date>
26
27 <chapter>
28 <title>Introduction</title>
29 <section>
30 <body>
31
32 <p>
33 This guide is based on an example with two IDE hard disks. It means that you
34 will more than likely need to change the drive, partition names and partition
35 sizes to match your own setup and needs.
36 </p>
37
38 <warn>
39 This document is not intended to be an LVM2 tutorial. It serves as a
40 supplement to the Gentoo installation procedure as described in the <uri
41 link="/doc/en/handbook/handbook-x86.xml?part=1&amp;chap=0">Handbook, Part
42 1</uri>. Make sure you <c>read</c> the Gentoo Installation Manual
43 <c>before</c> you start your installation process.
44 </warn>
45
46 <note>
47 For a complete LVM HOWTO point your browser to
48 <uri>http://tldp.org/HOWTO/LVM-HOWTO</uri>
49 </note>
50
51 </body>
52 </section>
53 <section>
54 <title>Initial requirements</title>
55 <body>
56
57 <p>
58 If you do a fresh install of Gentoo, you will need to use a bootable CD with
59 LVM2 support such as a Gentoo LiveCD. You can find the LiveCD for an x86
60 architecture on our <uri
61 link="http://www.gentoo.org/main/en/mirrors.xml">mirrors</uri> under
62 <path>/releases/x86/2004.0/livecd/universal</path>. Other architectures might
63 be supported as well.
64 </p>
65
66 <p>
67 It you install LVM2 on a currently running system with some spare hard disk
68 space, you will need to enable the LVM2 module (<path>dm-mod</path>). This
69 module is available in <path>gentoo-sources</path>, in
70 <path>development-sources</path> and in <path>gentoo-dev-sources</path>.
71 Compiling your kernel and getting LVM2 to work is covered later in this guide.
72 </p>
73
74 </body>
75 </section>
76 <section>
77 <title>Partitions</title>
78 <body>
79
80 <p>
81 Our example system has 2 IDE hard disks and will be partitioned as follows:
82 </p>
83
84 <ul>
85 <li>/dev/hda1 -- /boot</li>
86 <li>/dev/hda2 -- (swap)</li>
87 <li>/dev/hda3 -- /</li>
88 <li>/dev/hda4 -- Will be used by LVM2</li>
89 <li>/dev/hdb1 -- Will be used by LVM2</li>
90 </ul>
91
92 <impo>
93 Pay attention to the partition names as it is easy to confuse the a's and b's,
94 and the partition numbers. One false move could wipe out the wrong partition.
95 You have been warned!
96 </impo>
97
98 <p>
99 OK, time to start...
100 </p>
101
102 </body>
103 </section>
104 </chapter>
105
106 <chapter>
107 <title>Installation</title>
108 <section>
109 <body>
110
111 <p>
112 Follow the handbook until chapter <c>4. Preparing the Disks</c>
113 </p>
114
115 <p>
116 Use <c>fdisk</c> as described in the handbook, but use the partition scheme
117 mentioned above as an example. It is only <e>an example</e>, adapt it to your
118 own needs.
119 </p>
120
121 <p>
122 Create a small physical /boot partition (hda1). In this example, /boot will be
123 not managed by LVM2. This partition will contain your bootloader and your
124 kernel(s). A 64MB partition should be well enough for quite a few kernel
125 generations.
126 </p>
127
128 <p>
129 Create a swap partition (hda2) and activate it.
130 </p>
131
132 <pre caption="Activating the swap partition">
133 # <i>mkswap /dev/hda2</i>
134 # <i>swapon /dev/hda2</i>
135 </pre>
136
137 <p>
138 Create a / (root) partition (hda3). If you are interested in trying to put
139 your root partition under LVM management (which we do not recommend), see the
140 resources section at the end of this guide for a link to a mini-howto on how to
141 do this. The size of the root partition need not be large if you will keep
142 <path>/opt /usr /home /var</path> and <path>/tmp</path> in an LVM2 Volume Group
143 (vg). In this case, 150M is sufficient.
144 </p>
145
146 <note>
147 It is <b>not</b> recommended to put the following directories in an
148 LVM2 partition: <path>/etc</path>, <path>/lib</path>, <path>/mnt</path>,
149 <path>/proc</path>, <path>/sbin</path>, <path>/dev</path>, <path>/root</path>.
150 This way, you would still be able to log into your system (crippled, but
151 still somewhat usable, as root) if something goes terribly wrong.
152 </note>
153
154 <p>
155 Assuming the /boot, swap and root partitions do not use the whole physical disk,
156 create a fourth partition on this disk and set it to type 8e (Linux LVM).
157 If you have more physical drives you would like to use with LVM, create
158 one partition on each and give them the same type (8e).
159 </p>
160
161 <note>
162 Considering the huge size of current disks, you might consider splitting your
163 hard disks into smaller partitions instead of creating a big partition that
164 will be added to an LVM2 volume group in one block. LVM2 makes it easy to
165 extend your volumes after all. This leaves you some unallocated partitions you
166 might need to use outside of an LVM2 group. In short, don't use your disk space
167 until you know you need it. As an example, one contributor had split his
168 160&nbsp;Gb hard disk into 8 partitions of 20&nbsp;Gb each.
169 </note>
170
171 <p>
172 Load the LVM2 <path>dm-mod</path> module. For some reason, this module has been
173 compiled into the kernel 2.6 (named <c>smp</c>) on the Gentoo LiveCD. If you
174 used this kernel instead of the default 2.4 (named <c>gentoo</c>), you can skip
175 this step or ignore the warning you will get.
176 </p>
177
178 <pre caption="Loading the LVM2 module">
179 # <i>modprobe dm-mod</i>
180 </pre>
181
182 <p>
183 Scan and activate LVM:
184 </p>
185
186 <pre caption="Activating LVM">
187 <comment>(Avoid scanning your cdrom)</comment>
188 # <i>echo 'devices { filter=["r/cdrom/"] }' >/etc/lvm/lvm.conf</i>
189 # <i>vgscan</i>
190 Reading all physical volumes. This may take a while...
191 No volume groups found
192 </pre>
193
194 <p>
195 Prepare the partitions.
196 </p>
197
198 <pre caption="Preparing the partitions">
199 # <i>pvcreate /dev/hda4 /dev/hdb1</i>
200 No physical volume label read from /dev/hda4
201 Physical volume "/dev/hda4" successfully created
202 No physical volume label read from /dev/hdb1
203 Physical volume "/dev/hdb1" successfully created
204 </pre>
205
206 <p>
207 Setup a volume group. A volume group is the result of combining several
208 physical units into a single logical device.
209 </p>
210
211 <p>
212 In our example, <path>/dev/hda1</path>, <path>/dev/hda2</path> and
213 <path>/dev/hda3</path> are the <path>/boot</path>, swap and root partitions so
214 we need to combine <path>/dev/hda4</path> and <path>/dev/hdb1</path>. It can be
215 done with a single command, but, as an example, we will create our volume group
216 and extend it.
217 </p>
218
219 <pre caption="Creating and extending a volume group">
220 <comment>(Create a volume group named vg)</comment>
221 # <i>vgcreate vg /dev/hda4</i>
222 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning)</comment>
223 Volume group "vg" successfully created
224 <comment>(Extending an existing volume group)</comment>
225 # <i>vgextend vg /dev/hdb1</i>
226 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning, again and later as well)</comment>
227 Volume group "vg" successfully extended
228 </pre>
229
230 <p>
231 Create the logical volumes. Logical volumes are the equivalent of partitions
232 you would create using fdisk in a non LVM2 environment. In our example, we
233 create the following partitions:
234 </p>
235
236 <table>
237 <tr>
238 <th>Directory</th>
239 <th>Size</th>
240 </tr>
241 <tr>
242 <ti>/usr</ti>
243 <ti>10 GB</ti>
244 </tr>
245 <tr>
246 <ti>/home</ti>
247 <ti>5 GB</ti>
248 </tr>
249 <tr>
250 <ti>/opt</ti>
251 <ti>5 GB</ti>
252 </tr>
253 <tr>
254 <ti>/var</ti>
255 <ti>10 GB</ti>
256 </tr>
257 <tr>
258 <ti>/tmp</ti>
259 <ti>2 GB</ti>
260 </tr>
261 </table>
262
263 <p>
264 Since we are going to use LVM2, we should not worry too much about partition
265 sizes because they can always be expanded as needed.
266 </p>
267
268 <note>
269 As Terje Kvernes commented, it is easier to increase the size of a partition
270 then to shrink it. You might want therefore to start with smaller partitions
271 and increase their size as needed.
272 </note>
273
274 <pre caption="Creating and extending logical volumes">
275 # <i>lvcreate -L10G -nusr vg</i>
276 Logical volume "usr" created <comment>(Further similar messages not displayed)</comment>
277 # <i>lvcreate -L5G -nhome vg</i>
278 # <i>lvcreate -L5G -nopt vg</i>
279 # <i>lvcreate -L10G -nvar vg</i>
280 # <i>lvcreate -L2G -ntmp vg</i>
281 <comment>(As an example, let's extend a logical volume with 5 extra Gbytes)</comment>
282 # <i>lvextend -L+5G /dev/vg/home</i>
283 </pre>
284
285 <p>
286 Create filesystems on the logical volumes the same way you would on a regular
287 partition. We use ext3 on the logical volumes but any filesystem of your
288 choice will work:
289 </p>
290
291 <pre caption="Creating the filesystems">
292 # <i>mke2fs -j /dev/vg/usr</i>
293 # <i>mke2fs -j /dev/vg/home</i>
294 # <i>mke2fs -j /dev/vg/opt</i>
295 # <i>mke2fs -j /dev/vg/var</i>
296 # <i>mke2fs -j /dev/vg/tmp</i>
297 </pre>
298
299 <p>
300 Mount your partitions as described in the handbook and mount your LVM2 logical
301 volumes as if they were partitions. Replace the usual <path>/dev/hdxx</path>
302 with <path>/dev/vg/logical_volumename</path>.
303 </p>
304
305 <pre caption="Mounting your logical volumes">
306 <comment>(Make sure you have mounted your root partition as described in the handbook first)</comment>
307 # <i>mkdir /mnt/gentoo/usr</i>
308 # <i>mount /dev/vg/usr /mnt/gentoo/usr</i>
309 # <i>mkdir /mnt/gentoo/home</i>
310 # <i>mount /dev/vg/home /mnt/gentoo/home</i>
311 # <i>mkdir /mnt/gentoo/opt</i>
312 # <i>mount /dev/vg/opt /mnt/gentoo/opt</i>
313 # <i>mkdir /mnt/gentoo/var</i>
314 # <i>mount /dev/vg/var /mnt/gentoo/var</i>
315 # <i>mkdir /mnt/gentoo/tmp</i>
316 # <i>mount /dev/vg/tmp /mnt/gentoo/tmp</i>
317 </pre>
318
319 <note>
320 The rest of the installation handbook is mostly unchanged so we shall not
321 walk you through it again except to point out differences.
322 </note>
323
324 <p>
325 When configuring your kernel, make sure to configure your kernel to
326 support LVM2. Select the LVM2 module as follows:
327 </p>
328
329 <pre caption="Selecting the LVM2 module in a kernel 2.4.x">
330 Multi-device support (RAID and LVM) ---&gt;
331 [*] Multiple devices driver support (RAID and LVM)
332 &lt; &gt; RAID support
333 <comment>(Note that LVM is not selected on purpose, this was for LVM1)</comment>
334 &lt; &gt; Logical volume manager (LVM) support
335 &lt;M&gt; Device-mapper support
336 &lt; &gt; Mirror (RAID-1) support
337 </pre>
338
339 <pre caption="Selecting the LVM2 module in a kernel 2.6.x">
340 Device Drivers ---&gt;
341 Multi-device support (RAID and LVM) ---&gt;
342 [*] Multiple devices driver support (RAID and LVM)
343 &lt; &gt; RAID support
344 &lt;M&gt; Device mapper support
345 </pre>
346
347 <p>
348 The compiled module is called <path>dm-mod.ko</path>
349 </p>
350
351 <p>
352 After you have built your kernel and installed its modules, add the following
353 line to your <path>/etc/modules.autoload.d/kernel-{KV}</path> where {KV}
354 represents your kernel version (2.4 or 2.6) so that the LVM2 module gets loaded
355 when your machine is booted:
356 </p>
357
358 <pre caption="Adding the LVM2 module into /etc/modules.autoload.d/kernel-2.6">
359 # <i>nano -w /etc/modules.autoload.d/kernel-2.6</i>
360 <comment>(Add the following line)</comment>
361 dm-mod
362 </pre>
363
364 <p>
365 Now, install the lvm2 package.
366 </p>
367
368 <impo>
369 Make sure your <path>/usr/src/linux</path> link points to the kernel sources you
370 are using because the lvm2 ebuild depends on the device-mapper ebuild which
371 will check the presence of a required source file under
372 <path>/usr/src/linux/include/linux</path>.
373 </impo>
374
375 <pre caption="Emerging the LVM2 package">
376 # <i>emerge lvm2</i>
377 <comment>(Prevent lvm2 from probing your cdrom)</comment>
378 # <i>echo 'devices { filter=["r/cdrom/"] }' >> /etc/lvm/lvm.conf</i>
379 </pre>
380
381 <p>
382 When editing your <path>/etc/fstab</path> file, follow the handbook and add
383 your LVM2 logical volumes as needed. Again, here are a few lines needed for
384 our example:
385 </p>
386
387 <pre caption="Extract of /etc/fstab">
388 /dev/hda1 /boot ext3 noauto,noatime 1 1
389 /dev/hda2 none swap sw 0 0
390 /dev/hda3 / ext3 noatime 0 0
391 # Logical volumes
392 /dev/vg/usr /usr ext3 noatime 0 0
393 /dev/vg/home /home ext3 noatime 0 0
394 /dev/vg/opt /opt ext3 noatime 0 0
395 /dev/vg/var /var ext3 noatime 0 0
396 /dev/vg/tmp /tmp ext3 noatime 0 0
397 </pre>
398
399 <p>
400 When you reach the end of the installation part of the handbook, don't forget
401 to umount all your LVM2 logical volumes as well and for a good measure run the
402 following command before you reboot:
403 </p>
404
405 <pre caption="Shutting down LVM2">
406 # <i>vgchange -an</i>
407 </pre>
408
409 <p>
410 Restart your machine and all partitions should be visible and mounted.
411 </p>
412
413 </body>
414 </section>
415 </chapter>
416
417 <chapter>
418 <title>Resources</title>
419 <section>
420 <body>
421
422 <ul>
423 <li>
424 The official <uri link="http://sources.redhat.com/lvm2">LVM2 home page</uri>
425 </li>
426 <li>
427 The <uri link="http://tldp.org/HOWTO/LVM-HOWTO">LVM Howto</uri>
428 </li>
429 <li>
430 Daniel Robbins's articles on LVM at IBM's DeveloperWorks:
431 <uri>http://www-106.ibm.com/developerworks/linux/library/l-lvm/?dwzone=linux</uri>
432 and
433 <uri>http://www-106.ibm.com/developerworks/linux/library/l-lvm2.html?dwzone=linux</uri>
434 </li>
435 <li>
436 How to boot your root FS off of LVM1:
437 <uri>http://www.the-infinite.org/archive/docs/lvm/howto-boot-off-root-lv.txt</uri>
438 </li>
439 </ul>
440
441 </body>
442 </section>
443 </chapter>
444
445 <chapter>
446 <title>Acknowledgements</title>
447 <section>
448 <body>
449
450 <p>
451 Thanks <mail link="bangert@gentoo.org">Thilo Bangert</mail> and <mail
452 link="terjekv@math.uio.no">Terje Kvernes</mail> for their help and comments on
453 this document.
454 </p>
455
456 </body>
457 </section>
458 </chapter>
459 </guide>

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