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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/lvm2.xml,v 1.23 2007/11/03 21:14:55 nightmorph Exp $ -->
3 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4
5 <guide link="/doc/en/lvm2.xml">
6 <title>Gentoo LVM2 installation</title>
7
8 <author title="Author">
9 <mail link="avi@CFFtechnologies.com">Avi Schwartz</mail>
10 </author>
11 <author title="Contributor">
12 <mail link="rajiv@gentoo.org">Rajiv Manglani</mail>
13 </author>
14 <author title="Editor">
15 <mail link="neysx@gentoo.org">Xavier Neys</mail>
16 </author>
17
18 <abstract>
19 This guide describes how to setup your Gentoo machine using the Logical Volume
20 Manager version 2 (LVM2).
21 </abstract>
22
23 <!-- The content of this document is licensed under the CC-BY-SA license -->
24 <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 <license/>
26
27 <version>2.6</version>
28 <date>2007-11-03</date>
29
30 <chapter>
31 <title>Introduction</title>
32 <section>
33 <body>
34
35 <p>
36 This guide is based on an example with two IDE hard disks. It means that you
37 will more than likely need to change the drive, partition names and partition
38 sizes to match your own setup and needs.
39 </p>
40
41 <warn>
42 This document is not intended to be an LVM2 tutorial. It serves as a
43 supplement to the Gentoo installation procedure as described in the <uri
44 link="/doc/en/handbook/handbook-x86.xml?part=1">Handbook, Part 1</uri>. Make
45 sure you <e>read</e> the Gentoo Installation Manual <e>before</e> you start
46 your installation process.
47 </warn>
48
49 <note>
50 For a complete LVM HOWTO point your browser to
51 <uri>http://tldp.org/HOWTO/LVM-HOWTO</uri>
52 </note>
53
54 </body>
55 </section>
56 <section>
57 <title>Initial requirements</title>
58 <body>
59
60 <p>
61 If you do a fresh install of Gentoo, you will need to use a bootable CD with
62 LVM2 support such as a Gentoo Installation CD. You can find the Installation CDs
63 for an x86 architecture on our <uri link="/main/en/mirrors.xml">mirrors</uri>
64 under <path>/releases/x86/current/installcd</path>. Other architectures might be
65 supported as well.
66 </p>
67
68 <p>
69 If you install LVM2 on a currently running system with some spare hard disk
70 space, you will need to enable the LVM2 module (<path>dm-mod</path>). This
71 module is available in <path>gentoo-sources</path>. Compiling your kernel and
72 getting LVM2 to work is covered later in this guide.
73 </p>
74
75 <p>
76 Not all 2.4 kernels provided by Gentoo support LVM2!
77 </p>
78
79 </body>
80 </section>
81 <section>
82 <title>Partitions</title>
83 <body>
84
85 <p>
86 Our example system has two IDE hard disks and will be partitioned as follows:
87 </p>
88
89 <ul>
90 <li>/dev/hda1 -- /boot</li>
91 <li>/dev/hda2 -- (swap)</li>
92 <li>/dev/hda3 -- /</li>
93 <li>/dev/hda4 -- Will be used by LVM2</li>
94 <li>/dev/hdb1 -- Will be used by LVM2</li>
95 </ul>
96
97 <impo>
98 Pay attention to the partition names as it is easy to confuse the a's and b's,
99 and the partition numbers. One false move could wipe out the wrong partition.
100 You have been warned!
101 </impo>
102
103 <p>
104 OK, time to start...
105 </p>
106
107 </body>
108 </section>
109 </chapter>
110
111 <chapter>
112 <title>Installation</title>
113 <section>
114 <body>
115
116 <p>
117 Follow the handbook, but with the following amendments to chapter <e>4.
118 Preparing the Disks</e>:
119 </p>
120
121 <p>
122 Use <c>fdisk</c> as described in the handbook, but use the partition scheme
123 mentioned above as an example. It is only <e>an example</e>, adapt it to your
124 own needs.
125 </p>
126
127 <p>
128 Create a small physical <path>/boot</path> partition (hda1). In this example,
129 <path>/boot</path> will be not managed by LVM2. This partition will contain
130 your bootloader and your kernel(s). A 64MB partition should be well enough for
131 quite a few kernel generations.
132 </p>
133
134 <p>
135 Create a swap partition (hda2).
136 </p>
137
138 <p>
139 Create a / (root) partition (hda3). If you are interested in trying to put your
140 root partition under LVM management (which we do not recommend), see the
141 resources section at the end of this guide for a link to a mini-howto on how to
142 do this. The size of the root partition need not be large if you will keep
143 <path>/opt /usr /home /var</path> and <path>/tmp</path> in an LVM2 Volume Group
144 (vg). In this case, 1GB should be sufficient.
145 </p>
146
147 <note>
148 It is <b>not</b> recommended to put the following directories in an
149 LVM2 partition: <path>/etc</path>, <path>/lib</path>, <path>/mnt</path>,
150 <path>/proc</path>, <path>/sbin</path>, <path>/dev</path>, and
151 <path>/root</path>. This way, you would still be able to log into your system
152 (crippled, but still somewhat usable, as root) if something goes terribly wrong.
153 </note>
154
155 <p>
156 Assuming the <path>/boot</path>, swap and root partitions do not use the whole
157 physical disk, create a fourth partition on this disk and set it to type 8e
158 (Linux LVM). If you have more physical drives you would like to use with LVM,
159 create one partition on each and give them the same type (8e).
160 </p>
161
162 <note>
163 Considering the huge size of current disks, you might consider splitting your
164 hard disks into smaller partitions instead of creating a big partition that
165 will be added to an LVM2 volume group in one block. LVM2 makes it easy to
166 extend your volumes after all. This leaves you some unallocated partitions you
167 might need to use outside of an LVM2 group. In short, don't use your disk space
168 until you know you need it. As an example, one contributor had split his
169 160&nbsp;Gb hard disk into 8 partitions of 20&nbsp;Gb each.
170 </note>
171
172 <p>
173 Create the filesystems on <path>/dev/hda1</path> and <path>/dev/hda3</path>,
174 and create and activate the swap on <path>/dev/hda2</path> as described in the
175 handbook.
176 </p>
177
178 <p>
179 Load the LVM2 <path>dm-mod</path> module.
180 </p>
181
182 <pre caption="Loading the LVM2 module">
183 # <i>modprobe dm-mod</i>
184 </pre>
185
186 <p>
187 Before scanning and activating LVM, you might want to edit
188 <path>/etc/lvm/lvm.conf</path> to exclude some devices. By default, LVM2 will
189 scan all devices, even your CDROM which can generate error messages. In the
190 following example, the line that allows scanning of all devices is replaced by
191 one that rejects every device but our two IDE disks.
192 </p>
193
194 <pre caption="Activating LVM">
195 <comment>(Avoid scanning all devices but our disks)</comment>
196 # <i>nano -w /etc/lvm/lvm.conf</i>
197 <comment>(Look for the following line)</comment>
198 filter = [ "a/.*/" ]
199 <comment>(Replace it with the following one to scan
200 /dev/hda and /dev/hdb and reject anything else)</comment>
201 filter = [ "a|/dev/hd[ab]|", "r/.*/" ]
202 <comment>(Save the file and quit nano)</comment>
203 # <i>vgscan</i>
204 Reading all physical volumes. This may take a while...
205 No volume groups found
206 <comment>(Make any previously set up volume groups available)</comment>
207 # <i>vgchange -a y</i>
208 </pre>
209
210 <p>
211 Prepare the partitions.
212 </p>
213
214 <pre caption="Preparing the partitions">
215 # <i>pvcreate /dev/hda4 /dev/hdb1</i>
216 No physical volume label read from /dev/hda4
217 Physical volume "/dev/hda4" successfully created
218 No physical volume label read from /dev/hdb1
219 Physical volume "/dev/hdb1" successfully created
220 </pre>
221
222 <p>
223 Setup a volume group. A volume group is the result of combining several
224 physical units into a single logical device.
225 </p>
226
227 <p>
228 In our example, <path>/dev/hda1</path>, <path>/dev/hda2</path> and
229 <path>/dev/hda3</path> are the <path>/boot</path>, swap and root partitions so
230 we need to combine <path>/dev/hda4</path> and <path>/dev/hdb1</path>. It can be
231 done with a single command, but, as an example, we will create our volume group
232 and extend it.
233 </p>
234
235 <pre caption="Creating and extending a volume group">
236 <comment>(Create a volume group named vg)</comment>
237 # <i>vgcreate vg /dev/hda4</i>
238 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning)</comment>
239 Volume group "vg" successfully created
240 <comment>(Extending an existing volume group)</comment>
241 # <i>vgextend vg /dev/hdb1</i>
242 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning, again and later as well)</comment>
243 Volume group "vg" successfully extended
244 </pre>
245
246 <p>
247 Create the logical volumes. Logical volumes are the equivalent of partitions
248 you would create using fdisk in a non LVM2 environment. In our example, we
249 create the following partitions:
250 </p>
251
252 <table>
253 <tr>
254 <th>Directory</th>
255 <th>Size</th>
256 </tr>
257 <tr>
258 <ti>/usr</ti>
259 <ti>10 GB</ti>
260 </tr>
261 <tr>
262 <ti>/home</ti>
263 <ti>5 GB</ti>
264 </tr>
265 <tr>
266 <ti>/opt</ti>
267 <ti>5 GB</ti>
268 </tr>
269 <tr>
270 <ti>/var</ti>
271 <ti>10 GB</ti>
272 </tr>
273 <tr>
274 <ti>/tmp</ti>
275 <ti>2 GB</ti>
276 </tr>
277 </table>
278
279 <p>
280 Since we are going to use LVM2, we should not worry too much about partition
281 sizes because they can always be expanded as needed.
282 </p>
283
284 <note>
285 As Terje Kvernes commented, it is easier to increase the size of a partition
286 then to shrink it. You might therefore want to start with smaller partitions
287 and increase their size as needed.
288 </note>
289
290 <pre caption="Creating and extending logical volumes">
291 # <i>lvcreate -L10G -nusr vg</i>
292 Logical volume "usr" created <comment>(Further similar messages not displayed)</comment>
293 # <i>lvcreate -L5G -nhome vg</i>
294 # <i>lvcreate -L5G -nopt vg</i>
295 # <i>lvcreate -L10G -nvar vg</i>
296 # <i>lvcreate -L2G -ntmp vg</i>
297 <comment>(As an example, let's extend a logical volume with 5 extra Gbytes)</comment>
298 # <i>lvextend -L+5G /dev/vg/home</i>
299 </pre>
300
301 <p>
302 Create filesystems on the logical volumes the same way you would on a regular
303 partition. We use ext3 on the logical volumes but any filesystem of your
304 choice will work:
305 </p>
306
307 <pre caption="Creating the filesystems">
308 # <i>mke2fs -j /dev/vg/usr</i>
309 # <i>mke2fs -j /dev/vg/home</i>
310 # <i>mke2fs -j /dev/vg/opt</i>
311 # <i>mke2fs -j /dev/vg/var</i>
312 # <i>mke2fs -j /dev/vg/tmp</i>
313 </pre>
314
315 <p>
316 Mount your partitions as described in the handbook and mount your LVM2 logical
317 volumes as if they were partitions. Replace the usual <path>/dev/hdxx</path>
318 with <path>/dev/vg/logical_volumename</path>.
319 </p>
320
321 <pre caption="Mounting your logical volumes">
322 <comment>(Make sure you have mounted your root partition as described in the handbook first)</comment>
323 # <i>mkdir /mnt/gentoo/usr</i>
324 # <i>mount /dev/vg/usr /mnt/gentoo/usr</i>
325 # <i>mkdir /mnt/gentoo/home</i>
326 # <i>mount /dev/vg/home /mnt/gentoo/home</i>
327 # <i>mkdir /mnt/gentoo/opt</i>
328 # <i>mount /dev/vg/opt /mnt/gentoo/opt</i>
329 # <i>mkdir /mnt/gentoo/var</i>
330 # <i>mount /dev/vg/var /mnt/gentoo/var</i>
331 # <i>mkdir /mnt/gentoo/tmp</i>
332 # <i>mount /dev/vg/tmp /mnt/gentoo/tmp</i>
333 </pre>
334
335 <note>
336 The rest of the installation handbook is mostly unchanged so we shall not
337 walk you through it again except to point out differences.
338 </note>
339
340 <p>
341 When configuring your kernel, make sure to configure your kernel to
342 support LVM2 (not all 2.4 kernels do). Select the LVM2 module as follows:
343 </p>
344
345 <pre caption="Selecting the LVM2 module in a 2.4.x kernel">
346 Multi-device support (RAID and LVM) ---&gt;
347 [*] Multiple devices driver support (RAID and LVM)
348 &lt; &gt; RAID support
349 <comment>(Note that LVM is not selected on purpose, this was for LVM1)</comment>
350 &lt; &gt; Logical volume manager (LVM) support
351 &lt;M&gt; Device-mapper support
352 &lt; &gt; Mirror (RAID-1) support
353 </pre>
354
355 <pre caption="Selecting the LVM2 module in a 2.6.x kernel">
356 Device Drivers ---&gt;
357 Multi-device support (RAID and LVM) ---&gt;
358 [*] Multiple devices driver support (RAID and LVM)
359 &lt; &gt; RAID support
360 &lt;M&gt; Device mapper support
361 </pre>
362
363 <p>
364 The compiled module is called <path>dm-mod.ko</path>
365 </p>
366
367 <p>
368 After you have built your kernel and installed its modules, add the following
369 line to your <path>/etc/modules.autoload.d/kernel-{KV}</path> where {KV}
370 represents your kernel version (2.4 or 2.6) so that the LVM2 module gets loaded
371 when your machine is booted:
372 </p>
373
374 <pre caption="Adding the LVM2 module into /etc/modules.autoload.d/kernel-2.6">
375 # <i>nano -w /etc/modules.autoload.d/kernel-2.6</i>
376 <comment>(Add the following line)</comment>
377 dm-mod
378 </pre>
379
380 <p>
381 Now, install the lvm2 package.
382 </p>
383
384 <impo>
385 Make sure your <path>/usr/src/linux</path> link points to the kernel sources you
386 are using because the lvm2 ebuild depends on the device-mapper ebuild which
387 will check the presence of a required source file under
388 <path>/usr/src/linux/include/linux</path>.
389 </impo>
390
391 <pre caption="Emerging the LVM2 package">
392 # <i>emerge lvm2</i>
393 </pre>
394
395 <p>
396 Edit <path>/etc/lvm/lvm.conf</path> as described <uri
397 link="#doc_chap2_pre2">earlier</uri>. The file you previously edited is part of
398 your installation environment and will disappear after the next reboot. This
399 time, you edit the real one inside your new Gentoo install.
400 </p>
401
402 <p>
403 When editing your <path>/etc/fstab</path> file, follow the handbook and add
404 your LVM2 logical volumes as needed. Again, here are a few lines needed for
405 our example:
406 </p>
407
408 <pre caption="Extract of /etc/fstab">
409 /dev/hda1 /boot ext3 noauto,noatime 1 2
410 /dev/hda2 none swap sw 0 0
411 /dev/hda3 / ext3 noatime 0 1
412 # Logical volumes
413 /dev/vg/usr /usr ext3 noatime 0 2
414 /dev/vg/home /home ext3 noatime 0 2
415 /dev/vg/opt /opt ext3 noatime 0 2
416 /dev/vg/var /var ext3 noatime 0 2
417 /dev/vg/tmp /tmp ext3 noatime 0 2
418 </pre>
419
420 <p>
421 When you reach the end of the installation part of the handbook, don't forget
422 to umount all your LVM2 logical volumes as well and for a good measure run the
423 following command before you reboot:
424 </p>
425
426 <pre caption="Shutting down LVM2">
427 # <i>vgchange -a n</i>
428 </pre>
429
430 <p>
431 Restart your machine and all partitions should be visible and mounted.
432 </p>
433
434 </body>
435 </section>
436 </chapter>
437
438 <chapter>
439 <title>Continuing After a Reboot</title>
440 <section>
441 <body>
442
443 <p>
444 If you have interrupted the Gentoo installation at one point and want to
445 continue, you need to create the volume device nodes first:
446 </p>
447
448 <pre caption="Reactivating the volumes">
449 # <i>vgscan --mknodes</i>
450 </pre>
451
452 <p>
453 Installation CDs with less recent tools might need to reactivate the volumes
454 instead:
455 </p>
456
457 <pre caption="Reactivating the volumes">
458 <comment>(Deactivate all volumes first)</comment>
459 # <i>vgchange -a n</i>
460 <comment>(Export all the volumes)</comment>
461 # <i>vgexport -a vg</i>
462 <comment>(Import all volumes)</comment>
463 # <i>vgimport -a vg</i>
464 <comment>(Reactivate all volumes)</comment>
465 # <i>vgchange -a y</i>
466 </pre>
467
468 </body>
469 </section>
470 </chapter>
471
472 <chapter>
473 <title>Resources</title>
474 <section>
475 <body>
476
477 <ul>
478 <li>
479 The official <uri link="http://sources.redhat.com/lvm2">LVM2 home page</uri>
480 </li>
481 <li>
482 The <uri link="http://tldp.org/HOWTO/LVM-HOWTO">LVM Howto</uri>
483 </li>
484 <li>
485 Daniel Robbins's articles on LVM for IBM's DeveloperWorks: <uri
486 link="/doc/en/articles/lvm-p1.xml">Part 1</uri> and <uri
487 link="/doc/en/articles/lvm-p2.xml">Part 2</uri>
488 </li>
489 <li>
490 How to boot your root FS off of LVM1:
491 <uri>http://www.the-infinite.org/archive/docs/lvm/howto-boot-off-root-lv.txt</uri>
492 </li>
493 </ul>
494
495 </body>
496 </section>
497 </chapter>
498
499 <chapter>
500 <title>Acknowledgements</title>
501 <section>
502 <body>
503
504 <p>
505 Thanks <mail link="bangert@gentoo.org">Thilo Bangert</mail> and <mail
506 link="terjekv@math.uio.no">Terje Kvernes</mail> for their help and comments on
507 this document.
508 </p>
509
510 </body>
511 </section>
512 </chapter>
513 </guide>

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