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1 <?xml version='1.0' encoding="UTF-8"?>
2 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
3
4 <guide link="/doc/en/xml-guide.xml">
5 <title>Gentoo Linux Genkernel Guide</title>
6
7 <author title="Author">
8 <mail link="plasmaroo@gentoo.org">Tim Yamin</mail>
9 </author>
10
11 <abstract>
12 This guide intends to provide a reference of all the functions
13 provided by Genkernel.
14 </abstract>
15
16 <license/>
17
18 <version>1.0</version>
19 <date>April 14, 2003</date>
20
21 <chapter>
22 <title>Introduction</title>
23 <section>
24 <title>Introduction</title>
25 <body>
26
27 <p>
28 Genkernel is designed to allow users who are not previously used to
29 compiling a kernel to use a similar setup to that one that is used on
30 the Gentoo LiveCDs which auto-detects your hardware.
31 </p>
32
33 <p>
34 Some users may also be interested in using genkernel for hardware
35 which requires initialization and a working kernel before it can be
36 booted. Because genkernel also automatically compiles your kernel modules,
37 thus allowing hardware which needs to be loaded with module parameters
38 to be used.
39 </p>
40
41 </body>
42 </section>
43 <section>
44 <title>Is genkernel for me?</title>
45 <body>
46
47 <p>
48 Genkernel is often a good choice to those who are unused to compiling
49 their own kernel or those who are not certain about their hardware
50 configurations.
51 </p>
52
53 <p>
54 Because genkernel is designed to use a generic configuration, it
55 should be able to support all of your hardware - however, because all
56 the drivers and modules have to be compiled as well, compiling a
57 kernel by yourself is often much faster provided you know what you need.
58 </p>
59
60 <p>
61 Genkernel does not however, currently support booting the sytem from
62 LVM2/EVMS2 partitions. Users are recommended to use a manually compiled
63 kernel for the time being.
64 </p>
65
66 </body>
67 </section>
68 <section>
69 <title>Getting genkernel</title>
70 <body>
71
72 <p>
73 You can obtain genkernel by simply running <c>emerge genkernel</c>. Don't
74 forget to use the <c>-k</c> flag for emerge if you are using binary packages,
75 i.e. GRP. Due to the GRP packages having an older version of genkernel, the
76 flags are different. As a result, you should consult the <uri
77 link="http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&amp;chap=9">
78 Gentoo Handbook</uri> and <path>genkernel --help</path>.
79 </p>
80
81 </body>
82 </section>
83 <section>
84 <title>Supported platforms</title>
85 <body>
86
87 <p>
88 As of genkernel 3.0.2; the following platforms should be
89 supported: alpha, amd64, parisc, parisc64, ppc, ppc64, sparc, sparc64, and x86. If
90 you believe that there is a bug with the support code, and not with
91 genkernel, please file a bug at the <uri
92 link="http://bugs.gentoo.org">Gentoo Bugzilla.</uri>
93 </p>
94
95 </body>
96 </section>
97 </chapter>
98
99 <chapter>
100 <title>Genkernel usage</title>
101 <section>
102 <title>Introduction</title>
103 <body>
104
105 <p>
106 Genkernel is designed to work in three modes:
107 </p>
108
109 <ul>
110 <li>"all" mode: this builds the kernel and the initrd</li>
111 <li>"kernel" mode: this only builds the kernel image</li>
112 <li>"initrd" mode: this only builds the initrd</li>
113 </ul>
114
115 <p>
116 Most users will only want the "all" mode, which runs the "kernel" mode
117 and the "initrd" mode for you. <b>Note</b> that the "kernel" and "initrd"
118 modes are currently just aliases for the "all" mode, so they will
119 currently give you no special effect.
120 </p>
121
122 <p>
123 Although genkernel is mainly a command to make your life easier when
124 you need to compile a kernel, genkernel is also packed full of
125 different flags which allow you to customize how your kernel is
126 compiled or configured.
127 </p>
128
129 </body>
130 </section>
131 <section>
132 <title>Genkernel compiler flags</title>
133 <body>
134
135 <p>
136 Genkernel supports the following flags which are passed to the
137 relevant applications when your kernel is assembled:
138 </p>
139
140 <ul>
141 <li>
142 <b>--kernel-as=<c>someAssembler</c></b>: This specifies an assembler which
143 would be used for compiling your kernel.
144 </li>
145 <li>
146 <b>--kernel-cc=<c>someCompiler</c></b>: This specifies a compiler which
147 would be used for compiling your kernel.
148 </li>
149 <li>
150 <b>--kernel-ld=<c>someLinker</c></b>: This specifies a linker which would
151 be used for compiling your kernel.
152 </li>
153 <li>
154 <b>--kernel-make=<c>someMake</c></b>: This specifies an alternate GNU Make
155 which would be used for compiling your kernel.
156 </li>
157 </ul>
158
159 <ul>
160 <li>
161 <b>--utils-as=<c>someAssembler</c></b>: This specifies an assembler which
162 would be used for compiling the support utilities.
163 </li>
164 <li>
165 <b>--utils-cc=<c>someCompiler</c></b>: This specifies a compiler which
166 would be used for compiling the support utilities.
167 </li>
168 <li>
169 <b>--utils-ld=<c>someLinker</c></b>: This specifies a linker which would be
170 used for compiling the support utilities.
171 </li>
172 <li>
173 <b>--utils-make=<c>someMake</c></b>: This specifies an alternate GNU Make
174 which would be used for compiling the support utilities.
175 </li>
176 </ul>
177
178 <ul>
179 <li>
180 <b>--makeopts=<c>-jJobs</c></b>: This specifies the flags which would be
181 passed to GNU Make when the kernel and utilities are being compiled.
182 </li>
183 </ul>
184
185 </body>
186 </section>
187 <section>
188 <title>Genkernel kernel flags</title>
189 <body>
190
191 <p>
192 Genkernel supports the following flags, some of which have
193 <c>--<b>no-</b>option</c> equivalents that influence
194 kernel compilation:
195 </p>
196
197 <ul>
198 <li>
199 <b>--callback="echo Hello"</b>: This routine calls the specified
200 arguments after the kernel and the relevant modules have been built; but
201 before the initrd has been built. This is useful where you might want
202 external modules installed to the initrd by emerging the relevant item
203 using the callback and then redefinining a Genkernel module group.
204 </li>
205 <li>
206 <b>--<c>no-</c>clean</b>: This runs <e>or does not
207 run</e> <c>make clean</c> before compiling your kernel. This
208 causes all object files and dependencies to be removed.
209 </li>
210 <li>
211 <b>--<c>no-</c>mrproper</b>: This runs <e>or does not
212 run</e> <c>make mrproper</c> before compiling your kernel. This
213 causes all object files, dependencies <b> and your
214 configuration</b> to be removed.
215 </li>
216 </ul>
217
218 <ul>
219 <li>
220 <b>--kerneldir=<path>/path/to/sources</path></b>: This specifies an
221 alternative kernel source location, instead of the default location of
222 <path>/usr/src/linux</path>.
223 </li>
224 <li>
225 <b>--kernel-config=<path>/path/to/config-file</path></b>: This specifies an
226 alternative kernel configuration which would be used; rather than the
227 inpersistant <path>/path/to/sources/.config</path> which is used by
228 default.
229 </li>
230 </ul>
231
232 <ul>
233 <li>
234 <b>--<c>no-</c>bootsplash</b>: This adds <e>or does not add</e> bootsplash
235 support in the initrd which genkernel builds. Not all architectures
236 currently support bootsplash, and a kernel that supports bootsplash is
237 also required.
238 </li>
239 <li>
240 <b>--<c>no-</c>menuconfig</b>: This runs <e>or does not run</e> the kernel
241 menu-based configurator before building your kernel, after <c>make
242 oldconfig</c> has ran.
243 </li>
244 </ul>
245
246 <ul>
247 <li>
248 <b>--no-initrdmodules</b>: This doesn't copy any modules to the initrd
249 which genkernel creates.
250 </li>
251 <li>
252 <b>--<c>no-</c>install</b>: This installs <e>or does not install</e> your
253 kernel, modules, and initrd one the compilation has finished.
254 </li>
255 </ul>
256
257 </body>
258 </section>
259 <section>
260 <title>Genkernel miscellaenous flags</title>
261 <body>
262
263 <p>
264 Genkernel also supports some miscellaneous flags which do not fit into
265 the other two categories:
266 </p>
267
268 <ul>
269 <li>
270 <b>--arch-override=<c>someArch</c></b>: This flag can be used to override
271 what architecture genkernel thinks you're on, if the auto-detection
272 mechanism fails (please file a bug if it does!) or if you wish to
273 cross-compile a kernel.
274 </li>
275 </ul>
276
277 <ul>
278 <li>
279 <b>--busybox-config=<path>/path/to/busybox-config</path></b>: This
280 overrides the default busybox configuration with the specifid file
281 </li>
282 <li>
283 <b>--busybox-bin=<path>/path/to/busybox-binary.tar.bz2</path></b>: Using
284 this option means that a busybox binary would not be compiled, and the
285 specified tarball would be used. Note that busybox <e>must</e> be compiled
286 statically!
287 </li>
288 </ul>
289
290 <ul>
291 <li>
292 <b>--minkernpackage=<path>/output/to/yourkernel.tar.bz2</path></b>: This
293 flag outputs a tarball of the kernel, named as <path>kernel</path> and the
294 initrd named as <path>initrd</path> to the specified file. No path
295 information or modules will be includes in the tarball.
296 </li>
297 </ul>
298
299 </body>
300 </section>
301 <section>
302 <title>Running genkernel</title>
303 <body>
304
305 <p>
306 All that is needed to run genkernel is just genkernel with the
307 necessary flags as root. For example:
308 </p>
309
310 <pre caption="Running genkernel">
311 # genkernel --menuconfig --no-clean --no-install --bootsplash
312 <comment>(Would produce a kernel, asking you what how to configure it
313 to your desire, leaving alone any compiled object files, enabling
314 bootsplash support but not installing anything.)</comment>
315 </pre>
316
317 <p>
318 If you want genkernel to install your kernel as well, you must ensure
319 that your <path>/boot</path> partition is mounted - recent Genkernels
320 would automatically attempt to do this for you if MOUNTBOOT is set to
321 "yes" in <path>/etc/genkernel.conf</path>.
322 </p>
323
324 <pre caption="Mounting your /boot manually">
325 <comment>(If /boot is a valid entry in /etc/fstab:)</comment>
326 # mount /boot
327 <comment>(... otherwise for IDE disks:)</comment>
328 # mount /dev/hda1 /boot
329 <comment>(... and for SCSI disks:)</comment>
330 # mount /dev/sda1 /boot
331 </pre>
332
333 </body>
334 </section>
335 <section>
336 <title>Setting up genkernel to work with your bootloader</title>
337 <body>
338
339 <p>
340 To set up genkernel to work with your bootloader, three or four changes are
341 required to your bootloader configuration.
342 </p>
343
344 <ol>
345 <li>
346 Add <c>root=/dev/ram0</c> and <c>init=/linuxrc</c> to the
347 kernel parameters passed to the kernel image.
348 </li>
349 <li>
350 Add <c>real_root=/dev/hda3</c>, for example, to the kernel parameters
351 passed to the kernel image if <path>/dev/hda3</path> contains your root
352 partition.
353 </li>
354 <li>
355 If you are using bootsplash, add a suitable modeline such as
356 <c>vga=0x317</c> to the parameters passed to the kernel and also add
357 <c>splash=verbose</c> or <c>splash=silent</c> depending on the verboseness
358 you require from your bootsplash.
359 </li>
360 <li>
361 Add the initrd according to how your bootloader requires it: see the <uri
362 link="http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?part=1&amp;chap=9">Gentoo
363 Handbook</uri> for details on how you would do it for your bootloader.
364 </li>
365 </ol>
366
367 </body>
368 </section>
369 </chapter>
370
371 <chapter>
372 <title>Porting genkernel</title>
373 <section>
374 <title>Introduction</title>
375 <body>
376
377 <p>
378 Provided your architecture has all the required libraries and utilties
379 which genkernel requires, which includes but it not limited to a
380 working kernel for your architecture, working compiler suite, GNU
381 Make, and a working busybox distribution, you're all set to go!
382 </p>
383
384 <p>
385 For each architecture, genkernel uses
386 <path>/usr/share/genkernel/archName</path> for configuration files for
387 that architecture.
388 </p>
389
390 </body>
391 </section>
392 <section>
393 <title>How the system bootstrapping works</title>
394 <body>
395
396 <ol>
397 <li>
398 The bootloader loads the genkernel image, built to the specification of the
399 configuration files in the genkernel directories as well as the initrd
400 which is prepared by genkernel.
401 </li>
402 <li>
403 The kernel boots up, allocates a small amount of RAM in which busybox is
404 initialized, which probes the system with the modules in the modules_load
405 list for the architecture.
406 </li>
407 <li>
408 Once done, and providing that the <c>real_root</c> parameter which is the
409 root boot device as busybox sees things is found, the system is booted from
410 the device.
411 </li>
412 </ol>
413
414 </body>
415 </section>
416 <section>
417 <title>The configuration files</title>
418 <body>
419
420 <ul>
421 <li>
422 <path>busy-config</path>: This is the configuration which is used to build
423 busybox for your architecture.
424 </li>
425 <li>
426 <path>config.sh</path>: This is a shell script which sets various internal
427 genkernel variables. See one of the <path>config.sh</path> files for an
428 example.
429 </li>
430 <li>
431 <path>modules_load</path>: This is a file containing a space-delimited list
432 of modules which are loaded for SCSI, FireWire, ATARAID and PCMCIA support.
433 If none are available for your platform, leave the fields blank. See one of
434 the <path>modules_load</path> files for an example.
435 </li>
436 </ul>
437
438 <ul>
439 <li>
440 <path>kernel-config</path>: A default kernel configuration used for any
441 kernel version.
442 </li>
443 <li>
444 <path>kernel-config-2.4</path>: A default kernel configuration used for 2.4
445 series kernels.
446 </li>
447 <li>
448 <path>kernel-config-2.6</path>: A default kernel configuration used for 2.6
449 series kernels.
450 </li>
451 </ul>
452
453 </body>
454 </section>
455 </chapter>
456 </guide>

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