| 1 |
rane 06/07/16 22:34:47 |
| 2 |
|
| 3 |
Added: kernel-config.xml |
| 4 |
Log: |
| 5 |
#94955, now we have kernel configuration documentation |
| 6 |
|
| 7 |
Revision Changes Path |
| 8 |
1.1 xml/htdocs/doc/en/kernel-config.xml |
| 9 |
|
| 10 |
file : http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/doc/en/kernel-config.xml?rev=1.1&content-type=text/x-cvsweb-markup&cvsroot=gentoo |
| 11 |
plain: http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/doc/en/kernel-config.xml?rev=1.1&content-type=text/plain&cvsroot=gentoo |
| 12 |
|
| 13 |
Index: kernel-config.xml |
| 14 |
=================================================================== |
| 15 |
<?xml version="1.0" encoding="UTF-8"?> |
| 16 |
<!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/kernel-config.xml,v 1.1 2006/07/16 22:34:46 rane Exp $ --> |
| 17 |
<!DOCTYPE guide SYSTEM "/dtd/guide.dtd"> |
| 18 |
|
| 19 |
<guide link="/doc/en/kernel-config.xml"> |
| 20 |
<title>Gentoo Linux Kernel Configuration Guide</title> |
| 21 |
|
| 22 |
<author title="Author"> |
| 23 |
<mail link="dsd@g.o">Daniel Drake</mail> |
| 24 |
</author> |
| 25 |
<author title="Contributor"> |
| 26 |
<mail link="curtis119@g.o">Curtis Napier</mail> |
| 27 |
</author> |
| 28 |
<author title="Contributor"> |
| 29 |
<mail link="jdr@××××××.net">Justin Robinson</mail> |
| 30 |
</author> |
| 31 |
<author title="Contributor"> |
| 32 |
<mail link="rane@g.o">Łukasz Damentko</mail> |
| 33 |
</author> |
| 34 |
<author title="Editor"> |
| 35 |
<mail link="smithj@g.o">Jonathan Smith</mail> |
| 36 |
</author> |
| 37 |
|
| 38 |
<abstract> |
| 39 |
This document aims to introduce the concepts of manual kernel configuration, |
| 40 |
and to detail some of the most common configuration pitfalls. |
| 41 |
</abstract> |
| 42 |
|
| 43 |
<!-- The content of this document is licensed under the CC-BY-SA license --> |
| 44 |
<!-- See http://creativecommons.org/licenses/by-sa/2.5 --> |
| 45 |
<license/> |
| 46 |
|
| 47 |
<version>1.0</version> |
| 48 |
<date>2006-07-16</date> |
| 49 |
|
| 50 |
<chapter> |
| 51 |
<title>Introduction</title> |
| 52 |
<section> |
| 53 |
<body> |
| 54 |
|
| 55 |
<p> |
| 56 |
Gentoo provides two ways for you to handle kernel installation and upgrade: |
| 57 |
<e>automatic</e> (genkernel), and <e>manual</e>. Although the automatic method |
| 58 |
can be regarded as <e>easier</e> for the user, there are a number of reasons |
| 59 |
why a large proportion of Gentoo users choose to configure their kernel |
| 60 |
manually: greater flexibility, smaller kernel, shorter compilation time, |
| 61 |
learning experience, severe boredom, etc. |
| 62 |
</p> |
| 63 |
|
| 64 |
<p> |
| 65 |
This guide does not cover the automatic method (genkernel). If you'd prefer to |
| 66 |
use genkernel to compile and install your kernel, head over to the <uri |
| 67 |
link="/doc/en/genkernel.xml">Genkernel documentation</uri>. |
| 68 |
</p> |
| 69 |
|
| 70 |
<p> |
| 71 |
This guide does not attempt to document the manual configuration process from |
| 72 |
start to finish -- the configuration process relies upon a large degree of |
| 73 |
common sense, and a relatively high level of technical knowledge about your |
| 74 |
system. Instead, this document will introduce the concepts of manual |
| 75 |
configuration and detail the most common pitfalls which users face. |
| 76 |
</p> |
| 77 |
|
| 78 |
<p> |
| 79 |
This document is written with recent kernels in mind, for the most common |
| 80 |
computer architectures. Some details may differ for older kernels or more |
| 81 |
exotic architectures, but much of the content will still be relevant. |
| 82 |
</p> |
| 83 |
|
| 84 |
<p> |
| 85 |
At this point, you are assumed to have Linux kernel sources unpacked on your |
| 86 |
hard disk (usually somewhere under <c>/usr/src</c>), and you are expected to |
| 87 |
know how to enter the <c>menuconfig</c> configuration utility and move through |
| 88 |
the menu system. If you are not already at this stage, we do have other |
| 89 |
documentation available to help you. |
| 90 |
</p> |
| 91 |
|
| 92 |
<ul> |
| 93 |
<li> |
| 94 |
The <uri link="/doc/en/gentoo-kernel.xml">Kernel Guide</uri> lists the |
| 95 |
various kernel source packages we have available |
| 96 |
</li> |
| 97 |
<li> |
| 98 |
The <uri link="/doc/en/kernel-upgrade.xml">Kernel Upgrade Guide</uri> |
| 99 |
explains how to upgrade your kernel or switch from one to another. |
| 100 |
</li> |
| 101 |
<li> |
| 102 |
The <uri link="/doc/en/handbook/index.xml">Gentoo Handbook</uri> covers |
| 103 |
some aspects of kernel installation too. |
| 104 |
</li> |
| 105 |
</ul> |
| 106 |
|
| 107 |
</body> |
| 108 |
</section> |
| 109 |
</chapter> |
| 110 |
|
| 111 |
<chapter> |
| 112 |
<title>Configuration Concepts</title> |
| 113 |
<section> |
| 114 |
<title>The basics</title> |
| 115 |
<body> |
| 116 |
|
| 117 |
<p> |
| 118 |
The general process is actually rather simple: you are presented with a series |
| 119 |
of options, categorised into individual menus and sub-menus, and you select the |
| 120 |
hardware support and kernel features relevant for your system. |
| 121 |
</p> |
| 122 |
|
| 123 |
<p> |
| 124 |
The kernel includes a <e>default configuration</e>, which is presented to you |
| 125 |
the first time you run menuconfig on a particular set of sources. The defaults |
| 126 |
are generally broad and sensible, which means that the majority of users will |
| 127 |
only have to make a small number of changes to the base config. If you decide |
| 128 |
to disable an option that was enabled by default, make sure you have a |
| 129 |
relatively good understanding of exactly what that option does, and the |
| 130 |
consequences of disabling it. |
| 131 |
</p> |
| 132 |
|
| 133 |
<p> |
| 134 |
If this is your first time configuring a Linux kernel, you should probably aim |
| 135 |
to be conservative: don't be too adventurous, and aim to make as few |
| 136 |
modifications to the default settings as possible. At the same time, keep in |
| 137 |
mind that there are certain parts of the configuration which you absolutely |
| 138 |
must customise to your system setup to actually allow it to boot! |
| 139 |
</p> |
| 140 |
|
| 141 |
</body> |
| 142 |
</section> |
| 143 |
<section> |
| 144 |
<title>Built-in vs modular</title> |
| 145 |
<body> |
| 146 |
|
| 147 |
<p> |
| 148 |
Most configuration options are <e>tristate</e>: they can be either not built at |
| 149 |
all, built directly into your kernel (Y), or built as a module (M). Modules are |
| 150 |
stored externally on the filesystem, whereas built-in items are built directly |
| 151 |
into the kernel image itself. |
| 152 |
</p> |
| 153 |
|
| 154 |
<p> |
| 155 |
There is an important difference between built-in and modular: with a few |
| 156 |
exceptions, the kernel makes no attempt whatsoever to load any external modules |
| 157 |
when you might need them (it is left up to the user). While certain other parts |
| 158 |
of the system may have load-on-demand facilities, and there are some automatic |
| 159 |
module loading utilities available, it is recommended that you build hardware |
| 160 |
support and kernel features directly into the kernel. The kernel can then |
| 161 |
ensure the functionality and hardware support is available whenever it needs |
| 162 |
it. |
| 163 |
</p> |
| 164 |
|
| 165 |
<p> |
| 166 |
Of course, for some parts of the configuration, built-in is an absolute |
| 167 |
requirement. For example, if your root partition was an <c>ext2</c> filesystem, |
| 168 |
your system would not boot if ext2 was built as a module (the system would have |
| 169 |
to look on the root partition to find the ext2 module, but it cannot look on |
| 170 |
the root partition unless it already has ext2 support loaded!). |
| 171 |
</p> |
| 172 |
|
| 173 |
</body> |
| 174 |
</section> |
| 175 |
<section> |
| 176 |
<title>Hardware support</title> |
| 177 |
<body> |
| 178 |
|
| 179 |
<p> |
| 180 |
Beyond detecting the <e>architecture type</e> of your system, the configuration |
| 181 |
utility makes no attempt to identify which hardware is actually present in your |
| 182 |
system. While there are default settings for some hardware support, you almost |
| 183 |
certainly need to find and select the configuration options relevant to your |
| 184 |
system's hardware configuration. |
| 185 |
</p> |
| 186 |
|
| 187 |
<p> |
| 188 |
This simply requires knowledge of the components inside and connected to your |
| 189 |
computer, or for you to identify these components. For most internal |
| 190 |
components, you need to identify the <e>chipset</e> used on each one, rather |
| 191 |
than the retail product name. |
| 192 |
</p> |
| 193 |
|
| 194 |
<p> |
| 195 |
There are some utilities available that will help you. <c>lspci</c> (part of |
| 196 |
the <c>sys-apps/pciutils</c> package) will identify your PCI-based and |
| 197 |
AGP-based hardware, and this includes components built onto the motherboard |
| 198 |
itself. <c>lsusb</c> (from the <c>sys-apps/usbutils</c>) package will identify |
| 199 |
devices connected to USB ports. |
| 200 |
</p> |
| 201 |
|
| 202 |
<p> |
| 203 |
The situation is somewhat confused by varying degrees of standardisation in the |
| 204 |
hardware world. Unless you really deviate from the defaults, your IDE hard |
| 205 |
disks will "just work", as will your PS/2 or USB keyboard and mouse. You'll get |
| 206 |
basic VGA display support. However, some devices such as ethernet adapters are |
| 207 |
barely standardised at all, so you'll have to identify the ethernet chipset and |
| 208 |
select the appropriate hardware support for your specific card to get any |
| 209 |
network access at all. |
| 210 |
</p> |
| 211 |
|
| 212 |
<p> |
| 213 |
In addition, while some things just-about-work with the default settings, you |
| 214 |
may need to select more specialised options to get the full potential from your |
| 215 |
system. For example, if you do not enable the support for the appropriate IDE |
| 216 |
chipset, your IDE hard disks will run <e>very</e> slowly. |
| 217 |
</p> |
| 218 |
|
| 219 |
</body> |
| 220 |
</section> |
| 221 |
<section> |
| 222 |
<title>Kernel features</title> |
| 223 |
<body> |
| 224 |
|
| 225 |
<p> |
| 226 |
As well as hardware support, you also need to think in terms of the software |
| 227 |
features you require in your kernel. One important example of such a feature is |
| 228 |
filesystem support: you need to select support for the filesystems in use on |
| 229 |
your hard disk, as well as any filesystems you might be using on external |
| 230 |
storage (e.g. VFAT on USB flash disks). |
| 231 |
</p> |
| 232 |
|
| 233 |
<p> |
| 234 |
Another common example is advanced network functionality. If you want to do |
| 235 |
some kind of routing or firewalling, you need to ensure the relevant |
| 236 |
configuration items are included in your kernel config. |
| 237 |
</p> |
| 238 |
|
| 239 |
</body> |
| 240 |
</section> |
| 241 |
<section> |
| 242 |
<title>Ready?</title> |
| 243 |
<body> |
| 244 |
|
| 245 |
<p> |
| 246 |
Now that we've introduced the concepts, you should be able to start identifying |
| 247 |
your hardware and browsing through the configuration menus, selecting the |
| 248 |
required kernel options for your system. |
| 249 |
</p> |
| 250 |
|
| 251 |
<p> |
| 252 |
The rest of this page aims to clear up common areas of confusion, and provide |
| 253 |
advice for how to avoid common problems which users often run into. Good luck! |
| 254 |
</p> |
| 255 |
|
| 256 |
</body> |
| 257 |
</section> |
| 258 |
</chapter> |
| 259 |
|
| 260 |
<chapter> |
| 261 |
<title>Common problems and areas of confusion</title> |
| 262 |
|
| 263 |
<section> |
| 264 |
<title>SATA disks are SCSI</title> |
| 265 |
<body> |
| 266 |
|
| 267 |
<p> |
| 268 |
Most modern desktop systems ship with storage devices (hard disk and CD/DVD |
| 269 |
drives) on a <uri link="http://en.wikipedia.org/wiki/SATA">Serial ATA</uri> |
| 270 |
bus, rather than the older <uri |
| 271 |
link="http://en.wikipedia.org/wiki/Parallel_ATA">IDE</uri> (ribbon cable) bus |
| 272 |
type. |
| 273 |
</p> |
| 274 |
|
| 275 |
<p> |
| 276 |
SATA support in Linux is implemented in a layer referred to as <e>libata</e>, |
| 277 |
which sits below the SCSI subsystem. For this reason, SATA drivers are found in |
| 278 |
the SCSI driver section of the configuration. Additionally, your storage |
| 279 |
devices will be treated as SCSI devices, which means SCSI disk/cdrom support is |
| 280 |
required too. Your SATA hard disk will be named as (e.g.) <c>/dev/sda</c> and |
| 281 |
your SATA CD/DVD drive will be named as (e.g.) <c>/dev/sr0</c>. |
| 282 |
</p> |
| 283 |
|
| 284 |
<p> |
| 285 |
Although the majority of these drivers are for SATA controllers, libata was not |
| 286 |
designed to be SATA-specific. All common IDE drivers will also be ported to |
| 287 |
libata in the near future, and at this point, the above considerations will |
| 288 |
also apply for IDE users. |
| 289 |
</p> |
| 290 |
|
| 291 |
<pre caption="Configuration options for libata"> |
| 292 |
Device Drivers ---> |
| 293 |
SCSI device support ---> |
| 294 |
<*> SCSI device support |
| 295 |
<*> SCSI disk support |
| 296 |
<*> SCSI CDROM support |
| 297 |
|
| 298 |
SCSI low-level drivers ---> |
| 299 |
<*> Serial ATA (SATA) support |
| 300 |
<comment>Select your chipset from the choices listed below the above option</comment> |
| 301 |
</pre> |
| 302 |
|
| 303 |
</body> |
| 304 |
</section> |
| 305 |
<section> |
| 306 |
<title>IDE chipsets and DMA</title> |
| 307 |
<body> |
| 308 |
|
| 309 |
<p> |
| 310 |
Despite the introduction of SATA, IDE devices are still very common and |
| 311 |
depended upon by many. IDE is a fairly generic technology, and as such, Linux |
| 312 |
supports almost all IDE controllers out-of-the-box without any |
| 313 |
controller-specific options selected. |
| 314 |
</p> |
| 315 |
|
| 316 |
<p> |
| 317 |
However, IDE is an old technology, and in it's original <e>Programmed |
| 318 |
Input/Output</e> incarnation, it is unable to provide the transfer rates |
| 319 |
required for speedy access to modern storage devices. The generic IDE driver is |
| 320 |
limited to these PIO transfer modes, which result in slow data transfer rates, |
| 321 |
and significantly high CPU usage while data is being transferred to/from disk. |
| 322 |
</p> |
| 323 |
|
| 324 |
<p> |
| 325 |
Unless you're dealing with a pre-1995 system, your IDE controller will also |
| 326 |
support an alternative transfer mode, known as <e>Direct Memory Access</e> |
| 327 |
(DMA). DMA is much much faster, and CPU utilisation is barely affected while |
| 328 |
data transfers are taking place. If you are suffering from really poor general |
| 329 |
system performance and you are using an IDE disk, chances are that DMA is not |
| 330 |
being used. |
| 331 |
</p> |
| 332 |
|
| 333 |
<pre caption="Checking if DMA is enabled on your IDE disk"> |
| 334 |
# <i>hdparm -d /dev/hda</i> |
| 335 |
|
| 336 |
/dev/hda: |
| 337 |
using_dma = 0 (off) |
| 338 |
</pre> |
| 339 |
|
| 340 |
<p> |
| 341 |
To enable DMA on your IDE devices, you simply need to enable the configuration |
| 342 |
option for your IDE controller. |
| 343 |
</p> |
| 344 |
|
| 345 |
<pre caption="Configuration options for IDE controllers"> |
| 346 |
Device Drivers ---> |
| 347 |
ATA/ATAPI/MFM/RLL support ---> |
| 348 |
<*> ATA/ATAPI/MFM/RLL support |
| 349 |
<*> Enhanced IDE/MFM/RLL disk/cdrom/tape/floppy support |
| 350 |
[*] PCI IDE chipset support |
| 351 |
[*] Generic PCI bus-master DMA support |
| 352 |
[*] Use PCI DMA by default when available |
| 353 |
<comment>Select your chipset from the choices listed below the above option</comment> |
| 354 |
</pre> |
| 355 |
|
| 356 |
</body> |
| 357 |
</section> |
| 358 |
<section> |
| 359 |
<title>USB Host Controllers</title> |
| 360 |
<body> |
| 361 |
|
| 362 |
<p> |
| 363 |
<uri link="http://en.wikipedia.org/wiki/USB">USB</uri> is a widely adopted bus |
| 364 |
for connecting external peripherals to your computer. One of the reasons behind |
| 365 |
the success of USB is that it is a standardised protocol, however the USB |
| 366 |
<e>host controller devices</e> (HCDs) implemented on the host computer do vary |
| 367 |
a little. There are 3 main types: |
| 368 |
</p> |
| 369 |
|
| 370 |
<ul> |
| 371 |
<li> |
| 372 |
<c>UHCI</c> is the Universal Host Controller Interface. It supports USB |
| 373 |
1.1, and is usually found on motherboards based on a VIA or Intel chipset. |
| 374 |
</li> |
| 375 |
<li> |
| 376 |
<c>OHCI</c> is the Open Host Controller Interface. It supports USB 1.1 and |
| 377 |
is usually found on motherboards based on an Nvidia or SiS chipset. |
| 378 |
</li> |
| 379 |
<li> |
| 380 |
<c>EHCI</c> is the Extended Host Controller Interface. It is the only |
| 381 |
common host controller to support USB 2.0, and can typically be found on |
| 382 |
any computer that supports USB 2.0. |
| 383 |
</li> |
| 384 |
</ul> |
| 385 |
|
| 386 |
<p> |
| 387 |
Most systems will come with two of the above interface types: EHCI (USB 2.0), |
| 388 |
plus either UHCI or OHCI (USB 1.1). It is important that you select both types |
| 389 |
present on your system. While all USB 2.0 devices are backwards compatible with |
| 390 |
USB 1.1, a large proportion of USB devices (even the ones being manufactured |
| 391 |
today) are based on the USB 1.1 interface - why would a USB mouse need more |
| 392 |
than 1.5mbit/sec? |
| 393 |
</p> |
| 394 |
|
| 395 |
<p> |
| 396 |
If you do not select the relevant options corresponding to the USB HCD types |
| 397 |
present on your system, you may experience 'dead' USB ports: you plug a device |
| 398 |
in, but it does not get power or respond in any way. |
| 399 |
</p> |
| 400 |
|
| 401 |
<p> |
| 402 |
A neat <c>lspci</c> trick (from the <c>sys-apps/pciutils</c> package) makes it |
| 403 |
relatively easy to detect which HCDs are present in your system. Ignoring the |
| 404 |
FireWire controller which was also matched, it is easy to spot that my system |
| 405 |
requires OHCI and EHCI support: |
| 406 |
</p> |
| 407 |
|
| 408 |
<pre caption="Using lspci to detect HCD type"> |
| 409 |
# <i>lspci -v | grep HCI</i> |
| 410 |
00:02.0 USB Controller: nVidia Corporation CK804 USB Controller (rev a2) (prog-if 10 <i>[OHCI]</i>) |
| 411 |
00:02.1 USB Controller: nVidia Corporation CK804 USB Controller (rev a3) (prog-if 20 <i>[EHCI]</i>) |
| 412 |
01:0b.0 FireWire (IEEE 1394): Agere Systems FW323 (rev 61) (prog-if 10 [OHCI]) |
| 413 |
</pre> |
| 414 |
|
| 415 |
<pre caption="Configuration for USB HCDs"> |
| 416 |
Device Drivers ---> |
| 417 |
USB support ---> |
| 418 |
<*> Support for Host-side USB |
| 419 |
--- USB Host Controller Drivers |
| 420 |
<*> EHCI HCD (USB 2.0) support |
| 421 |
<*> OHCI HCD support |
| 422 |
<*> UHCI HCD (most Intel and VIA) support |
| 423 |
<comment>Select the HCDs present on your system, or all 3 if you are unsure.</comment> |
| 424 |
</pre> |
| 425 |
|
| 426 |
</body> |
| 427 |
</section> |
| 428 |
<section> |
| 429 |
<title>Multiprocessor, Hyper-Threading and Dual Core systems</title> |
| 430 |
<body> |
| 431 |
|
| 432 |
<p> |
| 433 |
Many computer systems are based on multiple processors, but not always in |
| 434 |
immediately obvious ways. |
| 435 |
</p> |
| 436 |
|
| 437 |
<ul> |
| 438 |
<li> |
| 439 |
Many of Intel's CPUs support a technology which they call <uri |
| 440 |
link="http://en.wikipedia.org/wiki/Hyperthreading">hyper-threading</uri>, |
| 441 |
which is where the CPU is actually viewed by the system as two |
| 442 |
<e>logical</e> processors. |
| 443 |
</li> |
| 444 |
<li> |
| 445 |
Some of the most recent Intel/AMD CPUs actually consist of multiple |
| 446 |
physical processors inside a single package, these are known as <uri |
| 447 |
link="http://en.wikipedia.org/wiki/Dual_core">dual core</uri> processors. |
| 448 |
</li> |
| 449 |
<li> |
| 450 |
Some high-end computer systems actually have multiple physical processors |
| 451 |
installed on specialised motherboards to provide a significant performance |
| 452 |
increase over a <e>uniprocessor</e> system. You'll probably know if you |
| 453 |
have such a system, since they aren't cheap. |
| 454 |
</li> |
| 455 |
</ul> |
| 456 |
|
| 457 |
<p> |
| 458 |
In all of these cases, you need to select the appropriate kernel options to |
| 459 |
obtain optimum performance from these setups. |
| 460 |
</p> |
| 461 |
|
| 462 |
<pre caption="Configuration for multi-processing"> |
| 463 |
Processor type and features ---> |
| 464 |
[*] Symmetric multi-processing support |
| 465 |
<comment>Select the above option if you are on a multi-processor system (of any type)</comment> |
| 466 |
[*] SMT (Hyperthreading) scheduler support |
| 467 |
<comment>Select the above option if you are on an Intel Hyper-Threading CPU</comment> |
| 468 |
[*] Multi-core scheduler support (NEW) |
| 469 |
<comment>Select the above option if your CPU is dual core</comment> |
| 470 |
</pre> |
| 471 |
|
| 472 |
</body> |
| 473 |
</section> |
| 474 |
<section> |
| 475 |
<title>x86 High Memory support</title> |
| 476 |
<body> |
| 477 |
|
| 478 |
<p> |
| 479 |
Due to limitations in the 32-bit address space of the x86 architecture, a |
| 480 |
kernel with default configuration can only support up to 896mb RAM. If your |
| 481 |
system has more memory, only the first 896mb will be visible, unless you enable |
| 482 |
high memory support. |
| 483 |
</p> |
| 484 |
|
| 485 |
<note> |
| 486 |
This limitation is specific to the x86 (IA32) architecture. Other architectures |
| 487 |
naturally support large amounts of memory, with no configuration tweaks |
| 488 |
required. |
| 489 |
</note> |
| 490 |
|
| 491 |
<p> |
| 492 |
High memory support is not enabled by default, because it introduces a small |
| 493 |
system overhead. Do not be distracted by this, the overhead is insignificant |
| 494 |
when compared to the performance increase of having more memory available! |
| 495 |
</p> |
| 496 |
|
| 497 |
<pre caption="Enabling high memory support on x86"> |
| 498 |
Processor type and features ---> |
| 499 |
High Memory Support ---> |
| 500 |
(X) 4GB |
| 501 |
( ) 64GB |
| 502 |
<comment>Choose the 4GB option, unless your system has more than 4GB of RAM.</comment> |
| 503 |
</pre> |
| 504 |
|
| 505 |
</body> |
| 506 |
</section> |
| 507 |
</chapter> |
| 508 |
|
| 509 |
<chapter> |
| 510 |
<title>Other kernel configuration documentation</title> |
| 511 |
<section> |
| 512 |
<body> |
| 513 |
|
| 514 |
<p> |
| 515 |
So far, we have only discussed general concepts and specific problems related |
| 516 |
to kernel configuration, without going into any precise details (such details |
| 517 |
are for you to discover!). However, other parts of the Gentoo documentation |
| 518 |
collection provide specialised details for the topics at hand. |
| 519 |
</p> |
| 520 |
|
| 521 |
<p> |
| 522 |
You may find these documents helpful while configuring those specific areas, |
| 523 |
but if you are new to kernel configuration, don't be too adventurous. Start by |
| 524 |
getting a basic system up and running, you can always come back later to add |
| 525 |
support for your audio, printing, etc. |
| 526 |
</p> |
| 527 |
|
| 528 |
<ul> |
| 529 |
<li> |
| 530 |
The <uri link="/doc/en/alsa-guide.xml">ALSA Guide</uri> details the |
| 531 |
configuration options required for sound card support. Note that ALSA is |
| 532 |
one exception to the suggested scheme of not building things as modules: |
| 533 |
ALSA is actually much easier to configure when the components are modular. |
| 534 |
</li> |
| 535 |
<li> |
| 536 |
The <uri link="/doc/en/bluetooth-guide.xml">Bluetooth Guide</uri> details |
| 537 |
the options you need in order to use bluetooth devices on your system. |
| 538 |
</li> |
| 539 |
<li> |
| 540 |
The <uri link="/doc/en/ipv6.xml">IPv6 Router Guide</uri> describes how to |
| 541 |
configure your kernel for routing using the next generation network |
| 542 |
addressing scheme. |
| 543 |
</li> |
| 544 |
<li> |
| 545 |
If you will be using the closed-source nVidia graphics drivers for improved |
| 546 |
3D graphics performance, the <uri link="/doc/en/nvidia-guide.xml">nVidia |
| 547 |
Guide</uri> lists the options that should and should not be selected on |
| 548 |
such a system. |
| 549 |
</li> |
| 550 |
<li> |
| 551 |
Amongst other things, the <uri |
| 552 |
link="/doc/en/power-management-guide.xml">Power Management Guide</uri> |
| 553 |
explains how to configure your kernel for CPU frequency scaling, and for |
| 554 |
suspend and hibernate functionality. |
| 555 |
</li> |
| 556 |
<li> |
| 557 |
If you are running a PowerPC system, the <uri |
| 558 |
link="/doc/en/gentoo-ppc-faq.xml">PPC FAQ</uri> has a few sections about |
| 559 |
kernel configuration. |
| 560 |
</li> |
| 561 |
<li> |
| 562 |
The <uri link="/doc/en/printing-howto.xml">Printing HOWTO</uri> lists the |
| 563 |
kernel options needed to support printing in Linux. |
| 564 |
</li> |
| 565 |
<li> |
| 566 |
The <uri link="/doc/en/usb-guide.xml">USB Guide</uri> details the |
| 567 |
configuration required to use common USB devices such as keyboards/mice, |
| 568 |
storage devices, and printers. |
| 569 |
</li> |
| 570 |
</ul> |
| 571 |
|
| 572 |
</body> |
| 573 |
</section> |
| 574 |
</chapter> |
| 575 |
|
| 576 |
<chapter> |
| 577 |
<title>Troubleshooting</title> |
| 578 |
<section> |
| 579 |
<title>Configuration changes do not take effect</title> |
| 580 |
<body> |
| 581 |
|
| 582 |
<p> |
| 583 |
It is very common for users to make a configuration change, but then make a |
| 584 |
small mistake in the process following on from that point. They reboot into a |
| 585 |
kernel image that is not the one they just reconfigured, observe that whatever |
| 586 |
problem they were trying to solve is still present, and conclude that the |
| 587 |
configuration change does not solve the problem. |
| 588 |
</p> |
| 589 |
|
| 590 |
<p> |
| 591 |
The process of compiling and installing kernels is outside the scope of this |
| 592 |
document, you should refer to the <uri link="/doc/en/kernel-upgrade.xml">Kernel |
| 593 |
Upgrade Guide</uri> for general guidance. In short, the process is: configure, |
| 594 |
compile, mount /boot (if not already mounted), copy new kernel image over, |
| 595 |
reboot. If you miss out any of those final stages, your changes will not take |
| 596 |
effect! |
| 597 |
</p> |
| 598 |
|
| 599 |
<p> |
| 600 |
It is possible to verify if you are booted from matches the kernel compiled on |
| 601 |
your hard disk by examining the date and time of compilation. Assuming your |
| 602 |
architecture is x86 and your kernel sources are installed at /usr/src/linux: |
| 603 |
</p> |
| 604 |
|
| 605 |
<pre caption="Verifying you are booted from your modified kernel"> |
| 606 |
# <i>uname -v</i> |
| 607 |
#4 SMP PREEMPT Sat Jul 15 08:49:26 BST 2006 |
| 608 |
<comment>The above command displays the date and time that the kernel you are currently booted from was compiled.</comment> |
| 609 |
|
| 610 |
# <i>ls -l /usr/src/linux/arch/i386/boot/bzImage</i> |
| 611 |
-rw-r--r-- 1 dsd users 1504118 Jul 15 08:49 /usr/src/linux/arch/i386/boot/bzImage |
| 612 |
<comment>The above command displays the date and time that the kernel image on your hard disk was last compiled.</comment> |
| 613 |
</pre> |
| 614 |
|
| 615 |
<p> |
| 616 |
If the two times from the above commands differ by more than 2 minutes, it |
| 617 |
indicates that you have made a mistake during kernel reinstallation and you are |
| 618 |
not booted from the kernel image that you thought you were! |
| 619 |
</p> |
| 620 |
|
| 621 |
</body> |
| 622 |
</section> |
| 623 |
<section> |
| 624 |
<title>Modules do not get loaded automatically</title> |
| 625 |
<body> |
| 626 |
|
| 627 |
<p> |
| 628 |
As mentioned earlier in this document, the kernel configuration system hides a |
| 629 |
large behavioural change when selecting a kernel component as a module (M) |
| 630 |
rather than built-in (Y). It is worth repeating this again because so many |
| 631 |
users fall into this trap. |
| 632 |
</p> |
| 633 |
|
| 634 |
<p> |
| 635 |
When you select a component as built-in, the code is built into the kernel |
| 636 |
image (bzImage). When the kernel needs to use that component, it can initialise |
| 637 |
and load it automatically, without any user intervention. |
| 638 |
</p> |
| 639 |
|
| 640 |
<p> |
| 641 |
When you select a component as a module, the code is built into a kernel module |
| 642 |
file and installed on your filesystem. In general, when the kernel needs to use |
| 643 |
that component, it can't! With some exceptions, the kernel makes no effort to |
| 644 |
actually load these modules - this task is left up to the user. |
| 645 |
</p> |
| 646 |
|
| 647 |
<p> |
| 648 |
So, if you build support for your network card as a module, and you then find |
| 649 |
that you cannot access your network, it is probably because the module is not |
| 650 |
loaded - you must either do this manually or configure your system to autoload |
| 651 |
it at boot time. |
| 652 |
</p> |
| 653 |
|
| 654 |
<p> |
| 655 |
Unless you have reasons to do otherwise, save yourself some time by building |
| 656 |
these components directly into the kernel image, so that the kernel can |
| 657 |
automatically set these things up for you. |
| 658 |
</p> |
| 659 |
|
| 660 |
</body> |
| 661 |
</section> |
| 662 |
</chapter> |
| 663 |
</guide> |
| 664 |
|
| 665 |
|
| 666 |
|
| 667 |
-- |
| 668 |
gentoo-doc-cvs@g.o mailing list |
Archives