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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/lvm2.xml,v 1.6 2004/08/29 12:34:09 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>2.0.4</version>
25 <date>September 09, 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 <p>
75 Not all 2.4 kernels provided by Gentoo support LVM2!
76 </p>
77
78 </body>
79 </section>
80 <section>
81 <title>Partitions</title>
82 <body>
83
84 <p>
85 Our example system has 2 IDE hard disks and will be partitioned as follows:
86 </p>
87
88 <ul>
89 <li>/dev/hda1 -- /boot</li>
90 <li>/dev/hda2 -- (swap)</li>
91 <li>/dev/hda3 -- /</li>
92 <li>/dev/hda4 -- Will be used by LVM2</li>
93 <li>/dev/hdb1 -- Will be used by LVM2</li>
94 </ul>
95
96 <impo>
97 Pay attention to the partition names as it is easy to confuse the a's and b's,
98 and the partition numbers. One false move could wipe out the wrong partition.
99 You have been warned!
100 </impo>
101
102 <p>
103 OK, time to start...
104 </p>
105
106 </body>
107 </section>
108 </chapter>
109
110 <chapter>
111 <title>Installation</title>
112 <section>
113 <body>
114
115 <p>
116 Follow the handbook until chapter <c>4. Preparing the Disks</c>
117 </p>
118
119 <p>
120 Use <c>fdisk</c> as described in the handbook, but use the partition scheme
121 mentioned above as an example. It is only <e>an example</e>, adapt it to your
122 own needs.
123 </p>
124
125 <p>
126 Create a small physical /boot partition (hda1). In this example, /boot will be
127 not managed by LVM2. This partition will contain your bootloader and your
128 kernel(s). A 64MB partition should be well enough for quite a few kernel
129 generations.
130 </p>
131
132 <p>
133 Create a swap partition (hda2) and activate it.
134 </p>
135
136 <pre caption="Activating the swap partition">
137 # <i>mkswap /dev/hda2</i>
138 # <i>swapon /dev/hda2</i>
139 </pre>
140
141 <p>
142 Create a / (root) partition (hda3). If you are interested in trying to put
143 your root partition under LVM management (which we do not recommend), see the
144 resources section at the end of this guide for a link to a mini-howto on how to
145 do this. The size of the root partition need not be large if you will keep
146 <path>/opt /usr /home /var</path> and <path>/tmp</path> in an LVM2 Volume Group
147 (vg). In this case, 150M is sufficient.
148 </p>
149
150 <note>
151 It is <b>not</b> recommended to put the following directories in an
152 LVM2 partition: <path>/etc</path>, <path>/lib</path>, <path>/mnt</path>,
153 <path>/proc</path>, <path>/sbin</path>, <path>/dev</path>, <path>/root</path>.
154 This way, you would still be able to log into your system (crippled, but
155 still somewhat usable, as root) if something goes terribly wrong.
156 </note>
157
158 <p>
159 Assuming the /boot, swap and root partitions do not use the whole physical disk,
160 create a fourth partition on this disk and set it to type 8e (Linux LVM).
161 If you have more physical drives you would like to use with LVM, create
162 one partition on each and give them the same type (8e).
163 </p>
164
165 <note>
166 Considering the huge size of current disks, you might consider splitting your
167 hard disks into smaller partitions instead of creating a big partition that
168 will be added to an LVM2 volume group in one block. LVM2 makes it easy to
169 extend your volumes after all. This leaves you some unallocated partitions you
170 might need to use outside of an LVM2 group. In short, don't use your disk space
171 until you know you need it. As an example, one contributor had split his
172 160&nbsp;Gb hard disk into 8 partitions of 20&nbsp;Gb each.
173 </note>
174
175 <p>
176 Load the LVM2 <path>dm-mod</path> module. For some reason, this module has been
177 compiled into the kernel 2.6 (named <c>smp</c>) on the Gentoo LiveCD. If you
178 used this kernel instead of the default 2.4 (named <c>gentoo</c>), you can skip
179 this step or ignore the warning you will get.
180 </p>
181
182 <pre caption="Loading the LVM2 module">
183 # <i>modprobe dm-mod</i>
184 </pre>
185
186 <p>
187 Scan and activate LVM:
188 </p>
189
190 <pre caption="Activating LVM">
191 <comment>(Avoid scanning your cdrom)</comment>
192 # <i>echo 'devices { filter=["r/cdrom/"] }' >/etc/lvm/lvm.conf</i>
193 # <i>vgscan</i>
194 Reading all physical volumes. This may take a while...
195 No volume groups found
196 </pre>
197
198 <p>
199 Prepare the partitions.
200 </p>
201
202 <pre caption="Preparing the partitions">
203 # <i>pvcreate /dev/hda4 /dev/hdb1</i>
204 No physical volume label read from /dev/hda4
205 Physical volume "/dev/hda4" successfully created
206 No physical volume label read from /dev/hdb1
207 Physical volume "/dev/hdb1" successfully created
208 </pre>
209
210 <p>
211 Setup a volume group. A volume group is the result of combining several
212 physical units into a single logical device.
213 </p>
214
215 <p>
216 In our example, <path>/dev/hda1</path>, <path>/dev/hda2</path> and
217 <path>/dev/hda3</path> are the <path>/boot</path>, swap and root partitions so
218 we need to combine <path>/dev/hda4</path> and <path>/dev/hdb1</path>. It can be
219 done with a single command, but, as an example, we will create our volume group
220 and extend it.
221 </p>
222
223 <pre caption="Creating and extending a volume group">
224 <comment>(Create a volume group named vg)</comment>
225 # <i>vgcreate vg /dev/hda4</i>
226 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning)</comment>
227 Volume group "vg" successfully created
228 <comment>(Extending an existing volume group)</comment>
229 # <i>vgextend vg /dev/hdb1</i>
230 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning, again and later as well)</comment>
231 Volume group "vg" successfully extended
232 </pre>
233
234 <p>
235 Create the logical volumes. Logical volumes are the equivalent of partitions
236 you would create using fdisk in a non LVM2 environment. In our example, we
237 create the following partitions:
238 </p>
239
240 <table>
241 <tr>
242 <th>Directory</th>
243 <th>Size</th>
244 </tr>
245 <tr>
246 <ti>/usr</ti>
247 <ti>10 GB</ti>
248 </tr>
249 <tr>
250 <ti>/home</ti>
251 <ti>5 GB</ti>
252 </tr>
253 <tr>
254 <ti>/opt</ti>
255 <ti>5 GB</ti>
256 </tr>
257 <tr>
258 <ti>/var</ti>
259 <ti>10 GB</ti>
260 </tr>
261 <tr>
262 <ti>/tmp</ti>
263 <ti>2 GB</ti>
264 </tr>
265 </table>
266
267 <p>
268 Since we are going to use LVM2, we should not worry too much about partition
269 sizes because they can always be expanded as needed.
270 </p>
271
272 <note>
273 As Terje Kvernes commented, it is easier to increase the size of a partition
274 then to shrink it. You might want therefore to start with smaller partitions
275 and increase their size as needed.
276 </note>
277
278 <pre caption="Creating and extending logical volumes">
279 # <i>lvcreate -L10G -nusr vg</i>
280 Logical volume "usr" created <comment>(Further similar messages not displayed)</comment>
281 # <i>lvcreate -L5G -nhome vg</i>
282 # <i>lvcreate -L5G -nopt vg</i>
283 # <i>lvcreate -L10G -nvar vg</i>
284 # <i>lvcreate -L2G -ntmp vg</i>
285 <comment>(As an example, let's extend a logical volume with 5 extra Gbytes)</comment>
286 # <i>lvextend -L+5G /dev/vg/home</i>
287 </pre>
288
289 <p>
290 Create filesystems on the logical volumes the same way you would on a regular
291 partition. We use ext3 on the logical volumes but any filesystem of your
292 choice will work:
293 </p>
294
295 <pre caption="Creating the filesystems">
296 # <i>mke2fs -j /dev/vg/usr</i>
297 # <i>mke2fs -j /dev/vg/home</i>
298 # <i>mke2fs -j /dev/vg/opt</i>
299 # <i>mke2fs -j /dev/vg/var</i>
300 # <i>mke2fs -j /dev/vg/tmp</i>
301 </pre>
302
303 <p>
304 Mount your partitions as described in the handbook and mount your LVM2 logical
305 volumes as if they were partitions. Replace the usual <path>/dev/hdxx</path>
306 with <path>/dev/vg/logical_volumename</path>.
307 </p>
308
309 <pre caption="Mounting your logical volumes">
310 <comment>(Make sure you have mounted your root partition as described in the handbook first)</comment>
311 # <i>mkdir /mnt/gentoo/usr</i>
312 # <i>mount /dev/vg/usr /mnt/gentoo/usr</i>
313 # <i>mkdir /mnt/gentoo/home</i>
314 # <i>mount /dev/vg/home /mnt/gentoo/home</i>
315 # <i>mkdir /mnt/gentoo/opt</i>
316 # <i>mount /dev/vg/opt /mnt/gentoo/opt</i>
317 # <i>mkdir /mnt/gentoo/var</i>
318 # <i>mount /dev/vg/var /mnt/gentoo/var</i>
319 # <i>mkdir /mnt/gentoo/tmp</i>
320 # <i>mount /dev/vg/tmp /mnt/gentoo/tmp</i>
321 </pre>
322
323 <note>
324 The rest of the installation handbook is mostly unchanged so we shall not
325 walk you through it again except to point out differences.
326 </note>
327
328 <p>
329 When configuring your kernel, make sure to configure your kernel to
330 support LVM2 (not all 2.4 kernels do). Select the LVM2 module as follows:
331 </p>
332
333 <pre caption="Selecting the LVM2 module in a kernel 2.4.x">
334 Multi-device support (RAID and LVM) ---&gt;
335 [*] Multiple devices driver support (RAID and LVM)
336 &lt; &gt; RAID support
337 <comment>(Note that LVM is not selected on purpose, this was for LVM1)</comment>
338 &lt; &gt; Logical volume manager (LVM) support
339 &lt;M&gt; Device-mapper support
340 &lt; &gt; Mirror (RAID-1) support
341 </pre>
342
343 <pre caption="Selecting the LVM2 module in a kernel 2.6.x">
344 Device Drivers ---&gt;
345 Multi-device support (RAID and LVM) ---&gt;
346 [*] Multiple devices driver support (RAID and LVM)
347 &lt; &gt; RAID support
348 &lt;M&gt; Device mapper support
349 </pre>
350
351 <p>
352 The compiled module is called <path>dm-mod.ko</path>
353 </p>
354
355 <p>
356 After you have built your kernel and installed its modules, add the following
357 line to your <path>/etc/modules.autoload.d/kernel-{KV}</path> where {KV}
358 represents your kernel version (2.4 or 2.6) so that the LVM2 module gets loaded
359 when your machine is booted:
360 </p>
361
362 <pre caption="Adding the LVM2 module into /etc/modules.autoload.d/kernel-2.6">
363 # <i>nano -w /etc/modules.autoload.d/kernel-2.6</i>
364 <comment>(Add the following line)</comment>
365 dm-mod
366 </pre>
367
368 <p>
369 Now, install the lvm2 package.
370 </p>
371
372 <impo>
373 Make sure your <path>/usr/src/linux</path> link points to the kernel sources you
374 are using because the lvm2 ebuild depends on the device-mapper ebuild which
375 will check the presence of a required source file under
376 <path>/usr/src/linux/include/linux</path>.
377 </impo>
378
379 <pre caption="Emerging the LVM2 package">
380 # <i>emerge lvm2</i>
381 <comment>(Prevent lvm2 from probing your cdrom)</comment>
382 # <i>echo 'devices { filter=["r/cdrom/"] }' >> /etc/lvm/lvm.conf</i>
383 </pre>
384
385 <p>
386 When editing your <path>/etc/fstab</path> file, follow the handbook and add
387 your LVM2 logical volumes as needed. Again, here are a few lines needed for
388 our example:
389 </p>
390
391 <pre caption="Extract of /etc/fstab">
392 /dev/hda1 /boot ext3 noauto,noatime 1 1
393 /dev/hda2 none swap sw 0 0
394 /dev/hda3 / ext3 noatime 0 0
395 # Logical volumes
396 /dev/vg/usr /usr ext3 noatime 0 0
397 /dev/vg/home /home ext3 noatime 0 0
398 /dev/vg/opt /opt ext3 noatime 0 0
399 /dev/vg/var /var ext3 noatime 0 0
400 /dev/vg/tmp /tmp ext3 noatime 0 0
401 </pre>
402
403 <p>
404 When you reach the end of the installation part of the handbook, don't forget
405 to umount all your LVM2 logical volumes as well and for a good measure run the
406 following command before you reboot:
407 </p>
408
409 <pre caption="Shutting down LVM2">
410 # <i>vgchange -an</i>
411 </pre>
412
413 <p>
414 Restart your machine and all partitions should be visible and mounted.
415 </p>
416
417 </body>
418 </section>
419 </chapter>
420
421 <chapter>
422 <title>Resources</title>
423 <section>
424 <body>
425
426 <ul>
427 <li>
428 The official <uri link="http://sources.redhat.com/lvm2">LVM2 home page</uri>
429 </li>
430 <li>
431 The <uri link="http://tldp.org/HOWTO/LVM-HOWTO">LVM Howto</uri>
432 </li>
433 <li>
434 Daniel Robbins's articles on LVM at IBM's DeveloperWorks:
435 <uri>http://www-106.ibm.com/developerworks/linux/library/l-lvm/?dwzone=linux</uri>
436 and
437 <uri>http://www-106.ibm.com/developerworks/linux/library/l-lvm2.html?dwzone=linux</uri>
438 </li>
439 <li>
440 How to boot your root FS off of LVM1:
441 <uri>http://www.the-infinite.org/archive/docs/lvm/howto-boot-off-root-lv.txt</uri>
442 </li>
443 </ul>
444
445 </body>
446 </section>
447 </chapter>
448
449 <chapter>
450 <title>Acknowledgements</title>
451 <section>
452 <body>
453
454 <p>
455 Thanks <mail link="bangert@gentoo.org">Thilo Bangert</mail> and <mail
456 link="terjekv@math.uio.no">Terje Kvernes</mail> for their help and comments on
457 this document.
458 </p>
459
460 </body>
461 </section>
462 </chapter>
463 </guide>

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