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1 neysx 1.1 <?xml version='1.0' encoding="UTF-8"?>
2 swift 1.27 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/lvm2.xml,v 1.26 2011/06/16 21:35:48 nightmorph Exp $ -->
3 neysx 1.1 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4    
5 nightmorph 1.26 <guide>
6 neysx 1.1 <title>Gentoo LVM2 installation</title>
7 rane 1.16
8 neysx 1.1 <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 rane 1.16 <!-- The content of this document is licensed under the CC-BY-SA license -->
24     <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
25 neysx 1.1 <license/>
26    
27 swift 1.27 <version>4</version>
28     <date>2011-12-26</date>
29 neysx 1.1
30     <chapter>
31     <title>Introduction</title>
32     <section>
33     <body>
34 swift 1.4
35 neysx 1.1 <p>
36 swift 1.27 This guide is based on an example with two SATA hard disks. It means that you
37 neysx 1.1 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 neysx 1.15 link="/doc/en/handbook/handbook-x86.xml?part=1">Handbook, Part 1</uri>. Make
45 fox2mike 1.20 sure you <e>read</e> the Gentoo Installation Manual <e>before</e> you start
46 neysx 1.15 your installation process.
47 neysx 1.1 </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 swift 1.4
54 neysx 1.1 </body>
55     </section>
56     <section>
57     <title>Initial requirements</title>
58     <body>
59 swift 1.4
60 neysx 1.1 <p>
61     If you do a fresh install of Gentoo, you will need to use a bootable CD with
62 nightmorph 1.21 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 neysx 1.1 </p>
67    
68     <p>
69 aaby 1.10 If you install LVM2 on a currently running system with some spare hard disk
70 nightmorph 1.26 space, you will need to enable the LVM2 module (<path>dm-mod</path>) in the
71     kernel. This module is available in <path>gentoo-sources</path>. Compiling
72     your kernel and getting LVM2 to work is covered later in this guide.
73 neysx 1.1 </p>
74 swift 1.4
75 swift 1.7 <p>
76     Not all 2.4 kernels provided by Gentoo support LVM2!
77     </p>
78    
79 neysx 1.1 </body>
80     </section>
81     <section>
82     <title>Partitions</title>
83     <body>
84 swift 1.4
85 neysx 1.1 <p>
86 swift 1.27 Our example system has two SATA hard disks and will be partitioned as follows:
87 neysx 1.1 </p>
88    
89     <ul>
90 swift 1.27 <li>/dev/sda1 -- /boot</li>
91     <li>/dev/sda2 -- (swap)</li>
92     <li>/dev/sda3 -- /</li>
93     <li>/dev/sda4 -- Will be used by LVM2</li>
94     <li>/dev/sdb1 -- Will be used by LVM2</li>
95 neysx 1.1 </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 swift 1.4
107 neysx 1.1 </body>
108     </section>
109     </chapter>
110    
111     <chapter>
112     <title>Installation</title>
113     <section>
114     <body>
115    
116 swift 1.4 <p>
117 swift 1.24 Follow the handbook, but with the following amendments to chapter <e>4.
118 fox2mike 1.20 Preparing the Disks</e>:
119 swift 1.4 </p>
120 neysx 1.1
121 swift 1.4 <p>
122 neysx 1.1 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 swift 1.4 </p>
126 neysx 1.1
127 swift 1.4 <p>
128 swift 1.27 Create a small physical <path>/boot</path> partition (sda1). In this example,
129 neysx 1.17 <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 swift 1.4 </p>
133 neysx 1.1
134 swift 1.4 <p>
135 swift 1.27 Create a swap partition (sda2).
136 swift 1.4 </p>
137    
138     <p>
139 swift 1.27 Create a / (root) partition (sda3). If you are interested in trying to put your
140 neysx 1.14 root partition under LVM management (which we do not recommend), see the
141 neysx 1.1 resources section at the end of this guide for a link to a mini-howto on how to
142 neysx 1.14 do this. The size of the root partition need not be large if you will keep
143 neysx 1.1 <path>/opt /usr /home /var</path> and <path>/tmp</path> in an LVM2 Volume Group
144 neysx 1.14 (vg). In this case, 1GB should be sufficient.
145 swift 1.4 </p>
146 neysx 1.1
147     <note>
148 swift 1.24 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 neysx 1.1 </note>
154    
155 swift 1.4 <p>
156 neysx 1.17 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 swift 1.4 </p>
161 neysx 1.1
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 swift 1.4 <p>
173 swift 1.27 Create the filesystems on <path>/dev/sda1</path> and <path>/dev/sda3</path>,
174     and create and activate the swap on <path>/dev/sda2</path> as described in the
175 neysx 1.17 handbook.
176     </p>
177    
178     <p>
179 nightmorph 1.26 Start the lvm service.
180 swift 1.4 </p>
181 neysx 1.1
182 nightmorph 1.26 <pre caption="Starting the lvm service">
183     # <i>rc-config start lvm</i>
184     </pre>
185    
186     <p>
187     It is recommended to add the lvm service to the boot runlevel. This way LVM2
188     will be activated each time the system boots.
189     </p>
190    
191     <pre caption="Adding lvm to the boot runlevel">
192     # <i>rc-config add lvm boot</i>
193 neysx 1.1 </pre>
194    
195 swift 1.4 <p>
196 neysx 1.17 Before scanning and activating LVM, you might want to edit
197     <path>/etc/lvm/lvm.conf</path> to exclude some devices. By default, LVM2 will
198     scan all devices, even your CDROM which can generate error messages. In the
199 rane 1.19 following example, the line that allows scanning of all devices is replaced by
200 swift 1.27 one that rejects every device but our two SATA disks.
201 swift 1.4 </p>
202    
203 neysx 1.1 <pre caption="Activating LVM">
204 neysx 1.17 <comment>(Avoid scanning all devices but our disks)</comment>
205     # <i>nano -w /etc/lvm/lvm.conf</i>
206     <comment>(Look for the following line)</comment>
207     filter = [ "a/.*/" ]
208     <comment>(Replace it with the following one to scan
209 swift 1.27 /dev/sda and /dev/sdb and reject anything else)</comment>
210 neysx 1.17 filter = [ "a|/dev/hd[ab]|", "r/.*/" ]
211     <comment>(Save the file and quit nano)</comment>
212 neysx 1.1 # <i>vgscan</i>
213     Reading all physical volumes. This may take a while...
214     No volume groups found
215 neysx 1.9 <comment>(Make any previously set up volume groups available)</comment>
216     # <i>vgchange -a y</i>
217 neysx 1.1 </pre>
218    
219 swift 1.4 <p>
220 neysx 1.1 Prepare the partitions.
221 swift 1.4 </p>
222 neysx 1.1
223     <pre caption="Preparing the partitions">
224 swift 1.27 # <i>pvcreate /dev/sda4 /dev/sdb1</i>
225     No physical volume label read from /dev/sda4
226     Physical volume "/dev/sda4" successfully created
227     No physical volume label read from /dev/sdb1
228     Physical volume "/dev/sdb1" successfully created
229 neysx 1.1 </pre>
230    
231 swift 1.4 <p>
232 neysx 1.1 Setup a volume group. A volume group is the result of combining several
233     physical units into a single logical device.
234 swift 1.4 </p>
235 neysx 1.1
236     <p>
237 swift 1.27 In our example, <path>/dev/sda1</path>, <path>/dev/sda2</path> and
238     <path>/dev/sda3</path> are the <path>/boot</path>, swap and root partitions so
239     we need to combine <path>/dev/sda4</path> and <path>/dev/sdb1</path>. It can be
240 neysx 1.1 done with a single command, but, as an example, we will create our volume group
241     and extend it.
242     </p>
243    
244     <pre caption="Creating and extending a volume group">
245     <comment>(Create a volume group named vg)</comment>
246 swift 1.27 # <i>vgcreate vg /dev/sda4</i>
247 neysx 1.1 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning)</comment>
248     Volume group "vg" successfully created
249     <comment>(Extending an existing volume group)</comment>
250 swift 1.27 # <i>vgextend vg /dev/sdb1</i>
251 neysx 1.1 /etc/lvm/backup: fsync failed: Invalid argument <comment>(Ignore this warning, again and later as well)</comment>
252     Volume group "vg" successfully extended
253     </pre>
254    
255 swift 1.4 <p>
256 neysx 1.1 Create the logical volumes. Logical volumes are the equivalent of partitions
257     you would create using fdisk in a non LVM2 environment. In our example, we
258     create the following partitions:
259 swift 1.4 </p>
260 neysx 1.1
261     <table>
262     <tr>
263 swift 1.4 <th>Directory</th>
264     <th>Size</th>
265 neysx 1.1 </tr>
266     <tr>
267 swift 1.4 <ti>/usr</ti>
268     <ti>10 GB</ti>
269 neysx 1.1 </tr>
270     <tr>
271 swift 1.4 <ti>/home</ti>
272     <ti>5 GB</ti>
273 neysx 1.1 </tr>
274     <tr>
275 swift 1.4 <ti>/opt</ti>
276     <ti>5 GB</ti>
277 neysx 1.1 </tr>
278     <tr>
279 swift 1.4 <ti>/var</ti>
280     <ti>10 GB</ti>
281 neysx 1.1 </tr>
282     <tr>
283 swift 1.4 <ti>/tmp</ti>
284     <ti>2 GB</ti>
285 neysx 1.1 </tr>
286     </table>
287    
288     <p>
289     Since we are going to use LVM2, we should not worry too much about partition
290     sizes because they can always be expanded as needed.
291     </p>
292    
293     <note>
294     As Terje Kvernes commented, it is easier to increase the size of a partition
295 aaby 1.10 then to shrink it. You might therefore want to start with smaller partitions
296 neysx 1.1 and increase their size as needed.
297     </note>
298    
299     <pre caption="Creating and extending logical volumes">
300     # <i>lvcreate -L10G -nusr vg</i>
301     Logical volume "usr" created <comment>(Further similar messages not displayed)</comment>
302     # <i>lvcreate -L5G -nhome vg</i>
303     # <i>lvcreate -L5G -nopt vg</i>
304     # <i>lvcreate -L10G -nvar vg</i>
305     # <i>lvcreate -L2G -ntmp vg</i>
306 swift 1.5 <comment>(As an example, let's extend a logical volume with 5 extra Gbytes)</comment>
307     # <i>lvextend -L+5G /dev/vg/home</i>
308 neysx 1.1 </pre>
309    
310 swift 1.4 <p>
311 neysx 1.1 Create filesystems on the logical volumes the same way you would on a regular
312     partition. We use ext3 on the logical volumes but any filesystem of your
313     choice will work:
314 swift 1.4 </p>
315 neysx 1.1
316     <pre caption="Creating the filesystems">
317     # <i>mke2fs -j /dev/vg/usr</i>
318     # <i>mke2fs -j /dev/vg/home</i>
319     # <i>mke2fs -j /dev/vg/opt</i>
320     # <i>mke2fs -j /dev/vg/var</i>
321     # <i>mke2fs -j /dev/vg/tmp</i>
322     </pre>
323    
324 swift 1.4 <p>
325 neysx 1.1 Mount your partitions as described in the handbook and mount your LVM2 logical
326     volumes as if they were partitions. Replace the usual <path>/dev/hdxx</path>
327     with <path>/dev/vg/logical_volumename</path>.
328 swift 1.4 </p>
329 neysx 1.1
330     <pre caption="Mounting your logical volumes">
331     <comment>(Make sure you have mounted your root partition as described in the handbook first)</comment>
332     # <i>mkdir /mnt/gentoo/usr</i>
333     # <i>mount /dev/vg/usr /mnt/gentoo/usr</i>
334     # <i>mkdir /mnt/gentoo/home</i>
335     # <i>mount /dev/vg/home /mnt/gentoo/home</i>
336     # <i>mkdir /mnt/gentoo/opt</i>
337     # <i>mount /dev/vg/opt /mnt/gentoo/opt</i>
338     # <i>mkdir /mnt/gentoo/var</i>
339     # <i>mount /dev/vg/var /mnt/gentoo/var</i>
340     # <i>mkdir /mnt/gentoo/tmp</i>
341     # <i>mount /dev/vg/tmp /mnt/gentoo/tmp</i>
342     </pre>
343    
344     <note>
345     The rest of the installation handbook is mostly unchanged so we shall not
346     walk you through it again except to point out differences.
347     </note>
348    
349 swift 1.4 <p>
350 neysx 1.1 When configuring your kernel, make sure to configure your kernel to
351 swift 1.6 support LVM2 (not all 2.4 kernels do). Select the LVM2 module as follows:
352 swift 1.4 </p>
353 neysx 1.1
354 aaby 1.10 <pre caption="Selecting the LVM2 module in a 2.4.x kernel">
355 neysx 1.1 Multi-device support (RAID and LVM) ---&gt;
356     [*] Multiple devices driver support (RAID and LVM)
357     &lt; &gt; RAID support
358     <comment>(Note that LVM is not selected on purpose, this was for LVM1)</comment>
359     &lt; &gt; Logical volume manager (LVM) support
360     &lt;M&gt; Device-mapper support
361     &lt; &gt; Mirror (RAID-1) support
362     </pre>
363    
364 aaby 1.10 <pre caption="Selecting the LVM2 module in a 2.6.x kernel">
365 neysx 1.1 Device Drivers ---&gt;
366 nightmorph 1.26 Multiple devices driver support (RAID and LVM) ---&gt;
367 neysx 1.1 [*] Multiple devices driver support (RAID and LVM)
368     &lt; &gt; RAID support
369     &lt;M&gt; Device mapper support
370     </pre>
371    
372     <p>
373     The compiled module is called <path>dm-mod.ko</path>
374     </p>
375    
376     <p>
377     Now, install the lvm2 package.
378     </p>
379    
380     <impo>
381     Make sure your <path>/usr/src/linux</path> link points to the kernel sources you
382     are using because the lvm2 ebuild depends on the device-mapper ebuild which
383     will check the presence of a required source file under
384     <path>/usr/src/linux/include/linux</path>.
385     </impo>
386    
387     <pre caption="Emerging the LVM2 package">
388     # <i>emerge lvm2</i>
389 neysx 1.17 </pre>
390 neysx 1.9
391 neysx 1.17 <p>
392     Edit <path>/etc/lvm/lvm.conf</path> as described <uri
393     link="#doc_chap2_pre2">earlier</uri>. The file you previously edited is part of
394     your installation environment and will disappear after the next reboot. This
395     time, you edit the real one inside your new Gentoo install.
396     </p>
397 neysx 1.1
398 swift 1.4 <p>
399 neysx 1.1 When editing your <path>/etc/fstab</path> file, follow the handbook and add
400     your LVM2 logical volumes as needed. Again, here are a few lines needed for
401     our example:
402 swift 1.4 </p>
403 neysx 1.1
404     <pre caption="Extract of /etc/fstab">
405 swift 1.27 /dev/sda1 /boot ext3 noauto,noatime 1 2
406     /dev/sda2 none swap sw 0 0
407     /dev/sda3 / ext3 noatime 0 1
408 neysx 1.1 # Logical volumes
409 neysx 1.18 /dev/vg/usr /usr ext3 noatime 0 2
410     /dev/vg/home /home ext3 noatime 0 2
411     /dev/vg/opt /opt ext3 noatime 0 2
412     /dev/vg/var /var ext3 noatime 0 2
413     /dev/vg/tmp /tmp ext3 noatime 0 2
414 neysx 1.1 </pre>
415    
416 swift 1.4 <p>
417 neysx 1.1 When you reach the end of the installation part of the handbook, don't forget
418     to umount all your LVM2 logical volumes as well and for a good measure run the
419     following command before you reboot:
420 swift 1.4 </p>
421 neysx 1.1
422     <pre caption="Shutting down LVM2">
423 neysx 1.9 # <i>vgchange -a n</i>
424 neysx 1.1 </pre>
425    
426 swift 1.4 <p>
427 neysx 1.1 Restart your machine and all partitions should be visible and mounted.
428 swift 1.4 </p>
429    
430 neysx 1.1 </body>
431     </section>
432     </chapter>
433    
434     <chapter>
435 swift 1.13 <title>Continuing After a Reboot</title>
436     <section>
437     <body>
438    
439     <p>
440     If you have interrupted the Gentoo installation at one point and want to
441     continue, you need to create the volume device nodes first:
442     </p>
443    
444     <pre caption="Reactivating the volumes">
445     # <i>vgscan --mknodes</i>
446     </pre>
447    
448     <p>
449     Installation CDs with less recent tools might need to reactivate the volumes
450     instead:
451     </p>
452    
453     <pre caption="Reactivating the volumes">
454     <comment>(Deactivate all volumes first)</comment>
455     # <i>vgchange -a n</i>
456     <comment>(Export all the volumes)</comment>
457 nightmorph 1.25 # <i>vgexport -a</i>
458 swift 1.13 <comment>(Import all volumes)</comment>
459 nightmorph 1.25 # <i>vgimport -a</i>
460 swift 1.13 <comment>(Reactivate all volumes)</comment>
461     # <i>vgchange -a y</i>
462     </pre>
463    
464     </body>
465     </section>
466     </chapter>
467    
468     <chapter>
469 neysx 1.1 <title>Resources</title>
470     <section>
471     <body>
472 swift 1.4
473 neysx 1.1 <ul>
474 swift 1.4 <li>
475     The official <uri link="http://sources.redhat.com/lvm2">LVM2 home page</uri>
476     </li>
477     <li>
478     The <uri link="http://tldp.org/HOWTO/LVM-HOWTO">LVM Howto</uri>
479     </li>
480     <li>
481 neysx 1.17 Daniel Robbins's articles on LVM for IBM's DeveloperWorks: <uri
482     link="/doc/en/articles/lvm-p1.xml">Part 1</uri> and <uri
483     link="/doc/en/articles/lvm-p2.xml">Part 2</uri>
484 swift 1.4 </li>
485     <li>
486     How to boot your root FS off of LVM1:
487     <uri>http://www.the-infinite.org/archive/docs/lvm/howto-boot-off-root-lv.txt</uri>
488     </li>
489 neysx 1.1 </ul>
490    
491     </body>
492     </section>
493     </chapter>
494 swift 1.4
495 neysx 1.1 <chapter>
496     <title>Acknowledgements</title>
497     <section>
498     <body>
499    
500     <p>
501     Thanks <mail link="bangert@gentoo.org">Thilo Bangert</mail> and <mail
502     link="terjekv@math.uio.no">Terje Kvernes</mail> for their help and comments on
503     this document.
504     </p>
505    
506     </body>
507     </section>
508     </chapter>
509     </guide>

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