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CONFIG_DEVTMPFS is also needed but not mentioned in handbook yet. Introducing for x86 and amd64... other arches should check if the requirement is for them valid as well and update accordingly

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-x86+amd64-kernel.xml,v 1.46 2012/03/27 17:47:19 swift Exp $ -->
8
9 <sections>
10
11 <abstract>
12 The Linux kernel is the core of every distribution. This chapter
13 explains how to configure your kernel.
14 </abstract>
15
16 <version>17</version>
17 <date>2012-04-12</date>
18
19 <section>
20 <title>Timezone</title>
21 <body>
22
23 <p>
24 You first need to select your timezone so that your system knows where it is
25 located. Look for your timezone in <path>/usr/share/zoneinfo</path>, then copy
26 it to <path>/etc/localtime</path>. Please avoid the
27 <path>/usr/share/zoneinfo/Etc/GMT*</path> timezones as their names do not
28 indicate the expected zones. For instance, <path>GMT-8</path> is in fact
29 GMT+8.
30 </p>
31
32 <pre caption="Setting the timezone information">
33 # <i>ls /usr/share/zoneinfo</i>
34 <comment>(Suppose you want to use Europe/Brussels)</comment>
35 # <i>cp /usr/share/zoneinfo/Europe/Brussels /etc/localtime</i>
36 <comment>(Next set the timezone)</comment>
37 # <i>echo "Europe/Brussels" &gt; /etc/timezone</i>
38 </pre>
39
40 </body>
41 </section>
42 <section>
43 <title>Installing the Sources</title>
44 <subsection>
45 <title>Choosing a Kernel</title>
46 <body>
47
48 <p>
49 The core around which all distributions are built is the Linux kernel. It is the
50 layer between the user programs and your system hardware. Gentoo provides its
51 users several possible kernel sources. A full listing with description is
52 available at the <uri link="/doc/en/gentoo-kernel.xml">Gentoo Kernel
53 Guide</uri>.
54 </p>
55
56 <p>
57 For <keyval id="arch"/>-based systems we have <c>gentoo-sources</c>
58 (kernel source patched for extra features).
59 </p>
60
61 <p>
62 Choose your kernel source and install it using <c>emerge</c>.
63 </p>
64
65 <pre caption="Installing a kernel source">
66 # <i>emerge gentoo-sources</i>
67 </pre>
68
69 <p>
70 When you take a look in <path>/usr/src</path> you should see a symlink called
71 <path>linux</path> pointing to your kernel source. In this case, the installed
72 kernel source points to <c>gentoo-sources-<keyval id="kernel-version"/></c>.
73 Your version may be different, so keep this in mind.
74 </p>
75
76 <pre caption="Viewing the kernel source symlink">
77 # <i>ls -l /usr/src/linux</i>
78 lrwxrwxrwx 1 root root 12 Oct 13 11:04 /usr/src/linux -&gt; linux-<keyval id="kernel-version"/>
79 </pre>
80
81 <p>
82 Now it is time to configure and compile your kernel source. You can use
83 <c>genkernel</c> for this, which will build a generic kernel as used by the
84 Installation CD. We explain the "manual" configuration first though, as it is
85 the best way to optimize your environment.
86 </p>
87
88 <p>
89 If you want to manually configure your kernel, continue now with <uri
90 link="#manual">Default: Manual Configuration</uri>. If you want to use
91 <c>genkernel</c> you should read <uri link="#genkernel">Alternative: Using
92 genkernel</uri> instead.
93 </p>
94
95 </body>
96 </subsection>
97 </section>
98 <section id="manual">
99 <title>Default: Manual Configuration</title>
100 <subsection>
101 <title>Introduction</title>
102 <body>
103
104 <p>
105 Manually configuring a kernel is often seen as the most difficult procedure a
106 Linux user ever has to perform. Nothing is less true -- after configuring a
107 couple of kernels you don't even remember that it was difficult ;)
108 </p>
109
110 <p>
111 However, one thing <e>is</e> true: you must know your system when you start
112 configuring a kernel manually. Most information can be gathered by emerging
113 pciutils (<c>emerge pciutils</c>) which contains <c>lspci</c>. You will now
114 be able to use <c>lspci</c> within the chrooted environment. You may safely
115 ignore any <e>pcilib</e> warnings (like pcilib: cannot open
116 /sys/bus/pci/devices) that <c>lspci</c> throws out. Alternatively, you can run
117 <c>lspci</c> from a <e>non-chrooted</e> environment. The results are the same.
118 You can also run <c>lsmod</c> to see what kernel modules the Installation CD
119 uses (it might provide you with a nice hint on what to enable).
120 </p>
121
122 <p>
123 Now go to your kernel source directory and execute <c>make menuconfig</c>. This
124 will fire up an ncurses-based configuration menu.
125 </p>
126
127 <pre caption="Invoking menuconfig">
128 # <i>cd /usr/src/linux</i>
129 # <i>make menuconfig</i>
130 </pre>
131
132 <p>
133 You will be greeted with several configuration sections. We'll first list some
134 options you must activate (otherwise Gentoo will not function, or not function
135 properly without additional tweaks).
136 </p>
137
138 </body>
139 </subsection>
140 <subsection>
141 <title>Activating Required Options</title>
142 <body>
143
144 <p>
145 Make sure that every driver that is vital to the booting of your system (such as
146 SCSI controller, ...) is compiled <e>in</e> the kernel and not as a module,
147 otherwise your system will not be able to boot completely.
148 </p>
149
150 </body>
151 <body test="func:keyval('arch')='AMD64'">
152
153 <p>
154 We shall then select the exact processor type. The x86_64 kernel maintainer
155 strongly recommends users enable MCE features so that they are able to be
156 notified of any hardware problems. On x86_64, these errors are not printed to
157 <c>dmesg</c> like on other architectures, but to <path>/dev/mcelog</path>. This
158 requires the <c>app-admin/mcelog</c> package. Make sure you select IA32
159 Emulation if you want to be able to run 32-bit programs. Gentoo will install a
160 multilib system (mixed 32-bit/64-bit computing) by default, so this option is
161 required.
162 </p>
163
164 <note>
165 If you plan to use a non-multilib profile (for a pure 64-bit system), then you
166 don't have to select IA32 Emulation support. However, you'll also need to follow
167 the <uri link="?part=1&amp;chap=6#doc_chap2_sect2">instructions</uri> for
168 switching to a <uri link="/doc/en/gentoo-amd64-faq.xml">non-multilib
169 profile</uri>, as well as choosing the correct <uri
170 link="?part=1&amp;chap=10#doc_chap2_sect2">bootloader</uri>.
171 </note>
172
173 <pre caption="Selecting processor type and features">
174 Processor type and features --->
175 [ ] Machine Check / overheating reporting
176 [ ] Intel MCE Features
177 [ ] AMD MCE Features
178 Processor family (AMD-Opteron/Athlon64) --->
179 ( ) Opteron/Athlon64/Hammer/K8
180 ( ) Intel P4 / older Netburst based Xeon
181 ( ) Core 2/newer Xeon
182 ( ) Intel Atom
183 ( ) Generic-x86-64
184 Executable file formats / Emulations --->
185 [*] IA32 Emulation
186 </pre>
187
188 </body>
189 <body test="func:keyval('arch')='x86'">
190
191 <p>
192 Now select the correct processor family:
193 </p>
194
195 <pre caption="Selecting correct processor family">
196 Processor type and features ---&gt;
197 <comment>(Change according to your system)</comment>
198 (<i>Athlon/Duron/K7</i>) Processor family
199 </pre>
200
201 </body>
202 <body>
203
204 <p>
205 Next select <e>Maintain a devtmpfs file system to mount at /dev</e> so that
206 critical device files are already available early in the boot process.
207 </p>
208
209 <pre caption="Enabling devtmpfs support">
210 Device Drivers ---&gt;
211 Generic Driver Options ---&gt;
212 [*] Maintain a devtmpfs filesystem to mount at /dev
213 [ ] Automount devtmpfs at /dev, after the kernel mounted the rootfs
214 </pre>
215
216 <p>
217 Now go to <c>File Systems</c> and select support for the filesystems you use.
218 <e>Don't</e> compile them as modules, otherwise your Gentoo system will not be
219 able to mount your partitions. Also select <c>Virtual memory</c> and <c>/proc
220 file system</c>.
221 </p>
222
223 <pre caption="Selecting necessary file systems">
224 File systems ---&gt;
225 <comment>(Select one or more of the following options as needed by your system)</comment>
226 &lt;*&gt; Second extended fs support
227 &lt;*&gt; Ext3 journalling file system support
228 &lt;*&gt; The Extended 4 (ext4) filesystem
229 &lt;*&gt; Reiserfs support
230 &lt;*&gt; JFS filesystem support
231 &lt;*&gt; XFS filesystem support
232 ...
233 Pseudo Filesystems ---&gt;
234 [*] /proc file system support
235 [*] Virtual memory file system support (former shm fs)
236
237 <comment>(Enable GPT partition label support if you used that previously)</comment>
238 Partition Types ---&gt;
239 [*] Advanced partition selection
240 ...
241 [*] EFI GUID Partition support
242 </pre>
243
244 <p>
245 If you are using PPPoE to connect to the Internet or you are using a dial-up
246 modem, you will need the following options in the kernel:
247 </p>
248
249 <pre caption="Selecting PPPoE necessary drivers">
250 Device Drivers ---&gt;
251 Network device support ---&gt;
252 &lt;*&gt; PPP (point-to-point protocol) support
253 &lt;*&gt; PPP support for async serial ports
254 &lt;*&gt; PPP support for sync tty ports
255 </pre>
256
257 <p>
258 The two compression options won't harm but are not definitely needed, neither
259 does the <c>PPP over Ethernet</c> option, that might only be used by <c>ppp</c>
260 when configured to do kernel mode PPPoE.
261 </p>
262
263 <p>
264 If you require it, don't forget to include support in the kernel for your
265 ethernet card.
266 </p>
267
268 <p test="func:keyval('arch')='x86'">
269 If you have an Intel CPU that supports HyperThreading (tm), or you have a
270 multi-CPU system, you should activate "Symmetric multi-processing support":
271 </p>
272
273 <p test="func:keyval('arch')='AMD64'">
274 If you have a multi-CPU Opteron or a multi-core (e.g. AMD64 X2) system, you
275 should activate "Symmetric multi-processing support":
276 </p>
277
278 <pre caption="Activating SMP support">
279 Processor type and features ---&gt;
280 [*] Symmetric multi-processing support
281 </pre>
282
283 <note>
284 In multi-core systems, each core counts as one processor.
285 </note>
286
287 <p test="func:keyval('arch')='x86'">
288 If you have more than 4GB of RAM, you need to enable "High Memory Support
289 (64G)".
290 </p>
291
292 <p>
293 If you use USB Input Devices (like Keyboard or Mouse) don't forget to enable
294 those as well:
295 </p>
296
297 <pre caption="Activating USB Support for Input Devices">
298 Device Drivers ---&gt;
299 [*] HID Devices ---&gt;
300 &lt;*&gt; USB Human Interface Device (full HID) support
301 </pre>
302
303 </body>
304 <body test="func:keyval('arch')='x86'">
305
306 <p>
307 If you want PCMCIA support for your laptop, don't forget to enable
308 support for the PCMCIA card bridge present in your system:
309 </p>
310
311 <pre caption="Enabling PCMCIA support">
312 Bus options (PCI etc.) ---&gt;
313 PCCARD (PCMCIA/CardBus) support ---&gt;
314 &lt;*&gt; PCCard (PCMCIA/CardBus) support
315 <comment>(select 16 bit if you need support for older PCMCIA cards. Most people want this.)</comment>
316 &lt;*&gt; 16-bit PCMCIA support
317 [*] 32-bit CardBus support
318 <comment>(select the relevant bridges below)</comment>
319 *** PC-card bridges ***
320 &lt;*&gt; CardBus yenta-compatible bridge support (NEW)
321 &lt;*&gt; Cirrus PD6729 compatible bridge support (NEW)
322 &lt;*&gt; i82092 compatible bridge support (NEW)
323 </pre>
324
325 <p>
326 When you've finished configuring the kernel, continue with <uri
327 link="#compiling">Compiling and Installing</uri>.
328 </p>
329
330 </body>
331 </subsection>
332 <subsection id="compiling">
333 <title>Compiling and Installing</title>
334 <body>
335
336 <p>
337 Now that your kernel is configured, it is time to compile and install it. Exit
338 the configuration and start the compilation process:
339 </p>
340
341 <pre caption="Compiling the kernel">
342 # <i>make &amp;&amp; make modules_install</i>
343 </pre>
344
345 <p>
346 When the kernel has finished compiling, copy the kernel image to
347 <path>/boot</path>. Use whatever name you feel is appropriate for your kernel
348 choice and remember it as you will need it later on when you configure your
349 bootloader. Remember to replace <c><keyval id="kernel-name"/></c> with the
350 name and version of your kernel.
351 </p>
352
353 <pre caption="Installing the kernel">
354 # <i>cp arch/<keyval id="arch-sub"/>/boot/bzImage /boot/<keyval id="kernel-name"/></i>
355 </pre>
356
357 </body>
358 </subsection>
359 <subsection id="initramfs">
360 <title>(Optional) Building an Initramfs</title>
361 <body>
362
363 <p>
364 If you use a specific partition layout where important file system locations
365 (like <path>/usr</path> or <path>/var</path>) are on separate partitions, then
366 you will need to setup an initramfs so that this partition can be mounted before
367 it is needed.
368 </p>
369
370 <p>
371 Without an initramfs, you risk that the system will not boot up properly as the
372 tools that are responsible for mounting the file systems need information that
373 resides on those file systems. An initramfs will pull in the necessary files
374 into an archive which is used right after the kernel boots, but before the
375 control is handed over to the <c>init</c> tool. Scripts on the initramfs will
376 then make sure that the partitions are properly mounted before the system
377 continues booting.
378 </p>
379
380 <p>
381 To install an initramfs, install <c>genkernel</c> first, then have it
382 generate an initramfs for you.
383 </p>
384
385 <pre caption="Building an initramfs">
386 # <i>emerge genkernel</i>
387 # <i>genkernel --install initramfs</i>
388 </pre>
389
390 <p>
391 If you need specific support in the initramfs, such as lvm or raid, add in the
392 appropriate options to genkernel. See <c>genkernel --help</c> for more
393 information, or the next example which enables support for LVM and software raid
394 (mdadm):
395 </p>
396
397 <pre caption="Building an initramfs with support for LVM and software raid">
398 # <i>genkernel --lvm --mdadm --install initramfs</i>
399 </pre>
400
401 <p>
402 The initramfs will be stored in <path>/boot</path>. You can find the file by
403 simply listing the files starting with <path>initramfs</path>:
404 </p>
405
406 <pre caption="Checking the initramfs file name">
407 # <i>ls /boot/initramfs*</i>
408 </pre>
409
410 <p>
411 Now continue with <uri link="#kernel_modules">Kernel Modules</uri>.
412 </p>
413
414 </body>
415 </subsection>
416 </section>
417 <section id="genkernel">
418 <title>Alternative: Using genkernel</title>
419 <body>
420
421 <p>
422 If you are reading this section, you have chosen to use our <c>genkernel</c>
423 script to configure your kernel for you.
424 </p>
425
426 <p>
427 Now that your kernel source tree is installed, it's now time to compile your
428 kernel by using our <c>genkernel</c> script to automatically build a kernel for
429 you. <c>genkernel</c> works by configuring a kernel nearly identically to the
430 way our Installation CD kernel is configured. This means that when you use
431 <c>genkernel</c> to build your kernel, your system will generally detect all
432 your hardware at boot-time, just like our Installation CD does. Because
433 genkernel doesn't require any manual kernel configuration, it is an ideal
434 solution for those users who may not be comfortable compiling their own kernels.
435 </p>
436
437 <p>
438 Now, let's see how to use genkernel. First, emerge the genkernel ebuild:
439 </p>
440
441 <pre caption="Emerging genkernel">
442 # <i>emerge genkernel</i>
443 </pre>
444
445 <p>
446 Now, compile your kernel sources by running <c>genkernel all</c>. Be aware
447 though, as <c>genkernel</c> compiles a kernel that supports almost all
448 hardware, this compilation will take quite a while to finish!
449 </p>
450
451 <p>
452 Note that, if your boot partition doesn't use ext2 or ext3 as filesystem you
453 might need to manually configure your kernel using <c>genkernel --menuconfig
454 all</c> and add support for your filesystem <e>in</e> the kernel (i.e.
455 <e>not</e> as a module). Users of LVM2 will probably want to add <c>--lvm2</c>
456 as an argument as well.
457 </p>
458
459 <pre caption="Running genkernel">
460 # <i>genkernel all</i>
461 </pre>
462
463 <p>
464 Once <c>genkernel</c> completes, a kernel, full set of modules and
465 <e>initial ram disk</e> (initramfs) will be created. We will use the kernel
466 and initrd when configuring a boot loader later in this document. Write
467 down the names of the kernel and initrd as you will need it when writing
468 the bootloader configuration file. The initrd will be started immediately after
469 booting to perform hardware autodetection (just like on the Installation CD)
470 before your "real" system starts up.
471 </p>
472
473 <pre caption="Checking the created kernel image name and initrd">
474 # <i>ls /boot/kernel* /boot/initramfs*</i>
475 </pre>
476
477 </body>
478 </section>
479 <section id="kernel_modules">
480 <title>Kernel Modules</title>
481
482 <subsection>
483 <include href="hb-install-kernelmodules.xml"/>
484 </subsection>
485
486 </section>
487 </sections>

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