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1 cam 1.24 <?xml version="1.0" encoding="UTF-8"?>
2     <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/genkernel.xml,v 1.23 2005/08/18 11:33:54 neysx Exp $ -->
3 swift 1.1 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4    
5 neysx 1.10 <guide link="/doc/en/genkernel.xml">
6 swift 1.1 <title>Gentoo Linux Genkernel Guide</title>
7    
8     <author title="Author">
9     <mail link="plasmaroo@gentoo.org">Tim Yamin</mail>
10     </author>
11    
12 plasmaroo 1.17 <!-- folajimi@speakeasy.net -->
13     <author title="Contributor">
14     Jimi Ayodele
15     </author>
16    
17     <!-- thseiler@gmail.com -->
18     <author title="NFS Support">
19     Thomas Seiler
20     </author>
21    
22 swift 1.1 <abstract>
23 plasmaroo 1.17 This guide intends to provide a reference of all the functions provided by
24 cam 1.24 genkernel.
25 swift 1.1 </abstract>
26    
27 plasmaroo 1.4 <license/>
28    
29 plasmaroo 1.22 <version>1.4.1</version>
30     <date>2005-08-11</date>
31 swift 1.1
32     <chapter>
33     <title>Introduction</title>
34     <section>
35 plasmaroo 1.17 <title>Rationale</title>
36 swift 1.1 <body>
37    
38     <p>
39 plasmaroo 1.17 For users who are not privy to kernel compilation, genkernel is a tool to
40     automate this process. It can help you create a kernel image akin to those
41     available on Gentoo Installation CDs, which are designed to auto-detect the
42     hardware configuration of your system. Some users may also be interested in
43     using genkernel for hardware requiring initialization and a working kernel
44     before the system starts up. Since genkernel automatically compiles your kernel
45     modules, you can use hardware that may require certain module parameters to be
46     loaded for proper operation.
47 swift 1.1 </p>
48    
49     </body>
50     </section>
51     <section>
52 plasmaroo 1.17 <title>Target Audience</title>
53 swift 1.1 <body>
54    
55     <p>
56 plasmaroo 1.17 If you are either uncertain about how to compile a kernel, or are just
57     unfamiliar with your hardware configuration, genkernel is a very handy tool.
58     It is designed to take the pain out of the kernel compiling process, and
59     supports most hardware by default.
60 swift 1.1 </p>
61    
62     <p>
63 plasmaroo 1.17 However, if you know what drivers are required by your system, you may be able
64     to further reduce the time taken to compile the kernel. This is possible since
65     you can direct genkernel to only build drivers relevant to your hardware.
66     Oftentimes, the number of drivers required by your system will be fewer
67     (implying a shorter kernel compilation time) than the default configuration
68     provides.
69 swift 1.1 </p>
70    
71     </body>
72     </section>
73     <section>
74 plasmaroo 1.17 <title>Installing genkernel</title>
75 swift 1.1 <body>
76    
77     <p>
78 plasmaroo 1.17 To obtain genkernel, run <c>emerge genkernel</c> from the command line. If you
79 neysx 1.23 are using the <uri
80 cam 1.24 link="/doc/en/handbook/2005.0/hb-install-about.xml#doc_chap2_sect1">Gentoo
81 neysx 1.23 Reference Platform</uri> (GRP), remember to install binary packages by passing
82     the <c>-k</c> flag to emerge. Since the GRP is bundled with an older version of
83     genkernel, the flags may be different. In any case, consult <c>genkernel
84     --help</c> for help on how to use the version of genkernel installed on your
85     system.
86 swift 1.1 </p>
87 cam 1.24
88 swift 1.1 </body>
89     </section>
90 plasmaroo 1.17 </chapter>
91    
92     <chapter>
93     <title>Working with genkernel</title>
94 swift 1.1 <section>
95 plasmaroo 1.17 <title>How to use genkernel</title>
96 swift 1.1 <body>
97    
98     <p>
99 plasmaroo 1.17 Although there are several ways to run genkernel, the least-intrusive approach
100     is provided by <c>genkernel all</c>. Here, a generic configuration which works
101     well for most systems is used. As was mentioned earlier, this approach is not
102     without drawbacks; most of the modules created are useless to the average user
103     and may increase compile time. Below is an illustration of a more efficient
104     approach, achieved by passing certain flags to genkernel as root:
105     </p>
106    
107     <pre caption="Running genkernel (with flags)">
108 neysx 1.23 # <i>genkernel --bootsplash --no-install --no-clean --menuconfig all</i>
109 plasmaroo 1.17 </pre>
110    
111     <p>
112     The above operation causes genkernel to create a bootsplash-enabled kernel
113     (<c>--bootsplash</c>) that will have to be manually installed
114     (<c>--no-install</c>). While preparing the kernel source tree, genkernel will
115     refrain from cleaning out any preexisting object files present in the source
116     tree (<c>--no-clean</c>). A menu-driven kernel configuration utility will be
117     displayed that allows the user to select which modules will be built for the
118     system (<c>--menuconfig</c>).
119     </p>
120    
121     <p>
122     There are other flags which alter the result provided by genkernel. For
123     instance, replacing <c>--no install</c> with the <c>--install</c> flag allows
124     genkernel to automatically install the new kernel in the <path>/boot</path>
125     directory. Using the <c>--mountboot</c> flag allows genkernel to mount your
126     <path>/boot</path> partition automatically, if necessary.
127     </p>
128    
129     <p>
130     Remember, genkernel is designed to make kernel compilation easy and
131     stress-free. For this reason, genkernel features several flags to ease the
132     kernel compilation effort. For example, there are flags to help with kernel
133     configuration, while others affect the actual compilation. Some flags even help
134     debug the compilation process. For those interested in further optimization,
135     there are flags that affect kernel assembling, packaging and even kernel
136     initialization.
137     </p>
138    
139     <p>
140     The rest of this chapter examines the functionality of various flags and
141     actions available for genkernel. Some of the flags have variants which perform
142     a converse operation. The converse variants carry the <b><c>no-</c></b> prefix,
143     and their effects are enclosed within the square brackets, [].
144 swift 1.1 </p>
145    
146     </body>
147     </section>
148     <section>
149 plasmaroo 1.17 <title>Configuration Flags</title>
150 swift 1.1 <body>
151    
152     <p>
153 plasmaroo 1.17 The configuration flags listed below exist to help you decide what features
154     should be enabled or disabled in the kernel prior to compilation. You can even
155     choose whether or not the configuration file created in the process should be
156     saved. The following are the primary configuration flags:
157 swift 1.1 </p>
158    
159     <ul>
160 neysx 1.23 <li>
161     <b>--<c>no-</c>menuconfig</b>: Activates <e>[or deactivates]</e> the
162     <c>make menuconfig</c> command (which invokes an interactive, menu-based
163     kernel configuration utility), before building the kernel.
164     </li>
165     <li>
166     <b>--gconfig</b>: Provides a kernel configuration utility which depends on
167     the GTK+ libraries. The advantage of this option is that most users find it
168     easier and clearer to configure the kernel using this tool, since it relies
169     on the X-windowing system. The disadvantage of this option is that you
170     <b>need</b> the X-windowing system to use it, so it will not work on the
171     command line.
172     </li>
173     <li>
174     <b>--xconfig</b>: Provides a kernel configuration utility which depends on
175     the QT libraries. The advantage of this option is that most users find it
176     easier and clearer to configure the kernel using this tool, since it relies
177     on the X-windowing system. The disadvantage of this option is that you
178     <b>need</b> the X-windowing system to use it, so it will not work on the
179     command line.
180     </li>
181     <li>
182     <b>--<c>no-</c>save-config</b>: Saves [or does not save] the kernel
183     configuration to a file in the <path>/etc/kernels/</path> directory for
184     later use.
185     </li>
186 swift 1.1 </ul>
187    
188     </body>
189     </section>
190     <section>
191 plasmaroo 1.17 <title>Compilation Flags</title>
192 swift 1.1 <body>
193    
194     <p>
195 plasmaroo 1.17 The following flags usually take effect during the actual compilation:
196 swift 1.1 </p>
197    
198     <ul>
199     <li>
200 neysx 1.23 <b>--kerneldir=<path>/path/to/sources/</path></b>: Specifies an alternative
201     kernel source location, rather than the default
202 plasmaroo 1.17 <path>/usr/src/linux/</path> location.
203 swift 1.1 </li>
204     <li>
205 plasmaroo 1.17 <b>--kernel-config=<path>/path/to/config-file</path></b>: Specifies what
206     alternative kernel configuration will be used, rather than the default
207     <path>/path/to/sources/.config</path> file.
208 swift 1.1 </li>
209     <li>
210 neysx 1.23 <b>--module-prefix=<path>/path/to/prefix-directory/</path></b>: Specifies a
211     prefix to the directory where kernel modules will be installed (default
212 plasmaroo 1.17 path is the <path>/lib/modules/</path> directory.)
213 swift 1.1 </li>
214     </ul>
215    
216     <ul>
217     <li>
218 neysx 1.23 <b>--<c>no-</c>clean</b>: Activates <e>[or deactivates]</e> the <c>make
219     clean</c> command before compiling your kernel. The <c>make clean</c>
220     command removes all object files and dependencies from the kernel's source
221     tree.
222 swift 1.1 </li>
223     <li>
224 neysx 1.23 <b>--<c>no-</c>mrproper</b>: Activates <e>[or deactivates]</e> the <c>make
225     mrproper</c> command before kernel compilation. Like the <c>make clean</c>
226     command, <c>make mrproper</c> removes all object files and dependencies
227     from the kernel's source tree. However, any previous configuration files
228     (in <path>/path/to/sources/.config</path> or
229     <path>/path/to/sources/.config.old</path>) will <b>also</b> be purged from
230     the kernel's source tree.
231 swift 1.1 </li>
232     <li>
233 plasmaroo 1.17 <b>--oldconfig</b>: Issues the <c>make oldconfig</c> command, which
234 neysx 1.23 attempts to collect configuration information for the system's architecture
235     from a generic script in <path>/usr/share/genkernel/</path>. This is a
236     non-interactive process; no user input is entertained. Also, if
237 plasmaroo 1.17 <c>--oldconfig</c> is used in conjunction with <c>--clean</c>, the latter
238 neysx 1.23 flag is negated, resulting in the activation of the <c>--no-clean</c> flag.
239 swift 1.1 </li>
240 plasmaroo 1.17 </ul>
241    
242     <ul>
243 neysx 1.23 <li>
244     <b>--callback="<c>echo hello</c>"</b>: Calls the specified arguments
245     (<c>echo hello</c>, in this case) after the kernel and the relevant modules
246     have been built, but before building the initrd image. This may be useful
247     if you want to install external modules in the initrd image by emerging the
248     relevant item(s) with the callback feature, and then redefining a genkernel
249     module group.
250     </li>
251 swift 1.1 </ul>
252    
253     <ul>
254 neysx 1.23 <li>
255     <b>--<c>no-</c>install</b>: Activates <e>[or deactivates]</e> the <c>make
256     install</c> command, which installs your new kernel image, configuration
257     file, initrd image and system map onto your mounted boot partition. Any
258     compiled modules will be installed as well.
259     </li>
260     <li>
261     <b>--<c>no-</c>initrdmodules</b>: Refrains from copying any modules to the
262     genkernel-created initrd image. This flag is an exception to the rule about
263     the <c>no-</c> prefix; omission of this prefix creates an invalid genkernel
264     flag.
265     </li>
266     <li>
267     <b>--genzimage</b>: Creates the initrd image, prior to the kernel image.
268     (This hack currently applies only to PPC Pegasos systems.)
269     </li>
270 swift 1.1 </ul>
271    
272     </body>
273     </section>
274     <section>
275 plasmaroo 1.17 <title>Compiler Flags</title>
276 swift 1.1 <body>
277    
278     <p>
279 plasmaroo 1.17 The following flags are supported by genkernel, and are passed to the relevant
280     applications while the kernel is being assembled. These flags affect the
281     <e>compiler</e> used for the kernel compilation process, albeit at a much lower
282     level.
283 swift 1.1 </p>
284    
285     <ul>
286 neysx 1.23 <li>
287     <b>--kernel-cc=<c>someCompiler</c></b>: Specifies the compiler employed
288     during the kernel compilation process.
289     </li>
290     <li>
291     <b>--kernel-ld=<c>someLinker</c></b>: Specifies the linker employed during
292     the kernel compilation process.
293     </li>
294     <li>
295     <b>--kernel-as=<c>someAssembler</c></b>: Specifies the assembler employed
296     during the kernel compilation process.
297     </li>
298     <li>
299     <b>--kernel-make=<c>someMake</c></b>: Specifies an alternative to the
300     <e>GNU make</e> utility employed during the kernel compilation process.
301     </li>
302 plasmaroo 1.17 </ul>
303    
304     <ul>
305 neysx 1.23 <li>
306     <b>--utils-cc=<c>someCompiler</c></b>: Specifies the compiler employed
307     during the compilation of support utilities.
308     </li>
309     <li>
310     <b>--utils-ld=<c>someLinker</c></b>: Specifies the linker employed during
311     the compilation of support utilities.
312     </li>
313     <li>
314     <b>--utils-as=<c>someAssembler</c></b>: Specifies the assembler employed
315     during the compilation of support utilities.
316     </li>
317     <li>
318     <b>--utils-make=<c>someMake</c></b>: Specifies an alternative to the <e>GNU
319     make</e> utility employed during the compilation of support utilities.
320     </li>
321 plasmaroo 1.17 </ul>
322    
323     <ul>
324 neysx 1.23 <li>
325     <b>--makeopts=<c>-jX</c></b>: Specifies the number of concurrent threads
326     that the make utility can implement while the kernel (and utilities) are
327     being compiled. The variable <b>'X'</b> is a number obtained by adding one
328     (1) to the number of CPUs used by the system. So, for a system with one
329     CPU, the appropriate flag is <c>-j2</c>; a system with two CPUs will use
330     the <c>-j3</c> flag, and so on. <e>(A system with one processor that
331     supports Hyper-Threading™ (HT) Technology can use the</e><c>-j3</c>
332     <e>flag, provided Symmetric Multi-Processing (SMP) support is enabled in
333     the kernel.)</e>
334     </li>
335 swift 1.1 </ul>
336    
337 plasmaroo 1.17 </body>
338     </section>
339     <section>
340     <title>Debugging Flags</title>
341     <body>
342    
343     <p>
344     The use debugging flags during the kernel compilation process controls the
345     amount of information reported, as well as the presentation of said data.
346     </p>
347    
348 swift 1.1 <ul>
349 neysx 1.23 <li>
350     <b>--debuglevel=<c>verblevel</c></b>: Controls the level of verbosity for
351     information provided by genkernel. The variable <c>verblevel</c> is an
352     integer between 0 and 5. The level '0' represents minimal output, while '5'
353     provides as much information as possible about genkernel's activities
354     during the kernel compilation process.
355     </li>
356     <li>
357     <b>--debugfile=<path>/path/to/outputfile</path></b>: Ignores the value set
358     by the <c>--debuglevel</c> argument, and sends <b>all</b> debugging data
359     produced by genkernel to the specified output file, which is located at
360     <path>/var/log/genkernel.log</path> by default.
361     </li>
362     <li>
363     <b>--no-color</b>: Activates [or deactivates] colored output of debugging
364     information (reported by genkernel) using escape sequences.
365     </li>
366 swift 1.1 </ul>
367    
368 plasmaroo 1.17 </body>
369     </section>
370    
371     <section>
372     <title>Initialization Flags</title>
373     <body>
374    
375     <p>
376     The flags here are used to create certain effects during system startup. Some
377     of these flags are primarily for aesthetics, while others may be essential for
378     enabling certain features on the system.
379     </p>
380    
381 swift 1.1 <ul>
382 neysx 1.23 <li>
383     <b>--<c>no-</c>bootsplash</b>: Activates <e>[or deactivates]</e> support
384     for <uri link="http://www.bootsplash.org/">bootsplash</uri> in the
385     genkernel-built initrd image. The bootsplash feature is supported on a
386     limited number of architectures, and a kernel that supports bootsplash is
387     also required.
388     </li>
389     <li>
390     <b>--<c>no-</c>gensplash</b>: Activates <e>[or deactivates]</e> support for
391     <uri
392     link="http://dev.gentoo.org/~spock/projects/gensplash/">gensplash</uri>
393     support in the genkernel-built initrd image. The gensplash utility is
394     intended to be a replacement for bootsplash, and is designed for use with
395     2.6.x series kernels. To override the default theme used by gensplash, use
396     <b>--gensplash=<c>PreferredTheme</c></b> (where <c>PreferredTheme</c> is
397     the title of one of the directories inside the <path>/etc/splash/</path>
398     directory.
399     </li>
400     <li>
401     <b>--gensplash-res=<c>PreferredResolution</c></b>: This flag allows you to
402     select which splash screen resolutions will be supported in the initrd
403     during the start-up of the system. This is useful for two reasons: First,
404     you are able to select only the splash screen resolution(s) relevant to
405     your system. Second, you avoid the unnecessary increase in the disk space
406     required by initrd (since the initrd does not have to support resolutions
407     that are irrelevant for your system configuration.) However, you may want
408     to omit this flag if the kernel is being compiled for an Installation CD;
409     this allows gensplash support for all possible resolutions.
410     </li>
411     <li>
412     <b>--do-keymap-auto</b>: Force keymap selection during the boot sequence.
413     </li>
414     <li>
415     <b>--lvm2</b>: Includes support for storage using via <uri
416     link="http://sources.redhat.com/lvm2/">Logical Volume Management</uri>
417     (LVM2) from <e>static</e> binaries, if available to the system. Relevant
418     (static) LVM2 binaries are compiled if they are unavailable. Be sure to
419     install the lvm2 package on your system with <c>emerge lvm2</c> before
420     enabling this flag, and review the <uri link="/doc/en/lvm2.xml">Gentoo LVM2
421     Installation</uri> guide.
422     </li>
423     <li>
424     <b>--evms2</b>: Includes support for storage using the <uri
425     link="http://evms.sourceforge.net/">Enterprise Volume Management
426     System</uri> (EVMS2), if available. Be sure to install the evms package on
427     your system with <c>USE=static emerge evms2</c> before using this
428     (genkernel) flag. <e>(Omitting the </e><c>USE=static</c> <e>flag during
429     package installation will fail to include the necessary static binaries.)
430     </e>
431     </li>
432     <li>
433     <b>--dmraid</b>: Includes support for <uri
434     link="http://people.redhat.com/~heinzm/sw/dmraid/readme">DMRAID</uri>; the
435     utility which creates RAID mappings using the kernel device-mapper
436     subsystem. DMRAID discovers, activates, deactivates and displays properties
437     of software RAID sets (ATARAID, for example) and contained DOS partitions.
438     </li>
439     <li>
440     <b>--linuxrc=/path/to/your/linuxrc</b>: Specifies a user-created
441     <e>linuxrc</e> — a script that is initialized during the start-up stage of
442     the kernel, prior to the actual boot process. (A default linuxrc script
443     should be in the <path>/usr/share/genkernel/</path> directory.) This script
444     allows you to boot into a small, modularized kernel and load the drivers
445     that are needed (as modules) by the system.
446     </li>
447     <li>
448     <b>--cachedir=/path/to/alt/dir/</b>: Overrides the default cache location
449     used while compiling the kernel.
450     </li>
451     <li>
452     <b>--tempdir=/path/to/new/tempdir/</b>: Specifies the location of the
453     temporary directory used by genkernel while compiling the kernel.
454     </li>
455     <li>
456     <b>--unionfs</b>: Includes support for the <uri
457     link="http://www.fsl.cs.sunysb.edu/project-unionfs.html">Unification File
458     System</uri> in the initrd image.
459     </li>
460 swift 1.1 </ul>
461    
462     </body>
463     </section>
464     <section>
465 plasmaroo 1.17 <title>Miscellaneous Flags</title>
466 swift 1.1 <body>
467    
468     <p>
469 plasmaroo 1.17 The assortment of flags listed below are supported by genkernel, but do not fit
470     neatly into any of the other categories:
471 swift 1.1 </p>
472    
473     <ul>
474 neysx 1.23 <li>
475     <b>--mountboot</b>: Detects whether or not the <path>/boot/</path>
476     directory needs to be mounted on a separate partition. It will check
477     <path>/etc/fstab</path> script for instructions on how to mount the boot
478     partition on a file system (if needed).
479     </li>
480     <li>
481     <b>--kernname=<c>NickName</c></b>: Allows you to modify the name of the
482     kernel and initrd images in the <path>/boot/</path> directory, so that the
483     images produced are kernel-<c>NickName</c>-version and
484     initramfs-<c>NickName</c>-version.
485     </li>
486 swift 1.1 </ul>
487    
488     </body>
489     </section>
490     <section>
491 plasmaroo 1.17 <title>Possible Actions</title>
492 swift 1.1 <body>
493    
494     <p>
495 plasmaroo 1.17 An action tells genkernel what to build. Currently, the following actions are
496     supported:
497 swift 1.1 </p>
498    
499 plasmaroo 1.17 <ul>
500 neysx 1.23 <li><c>initrd</c>: Only builds the initrd image</li>
501     <li><c>bzImage</c>: Only builds the kernel image</li>
502     <li><c>kernel</c>: Only builds the kernel image and modules</li>
503     <li><c>all</c>: Builds all stages — the initrd, kernel image and modules.</li>
504 plasmaroo 1.17 </ul>
505 swift 1.1
506     <p>
507 plasmaroo 1.17 The last action, <c>all</c>, is recommended for most users since it builds the
508     stages required for a functional kernel. Remember, an <e>action</e> simply
509     tells genkernel what to <e>build</e>, not <e>install</e>.
510 swift 1.1 </p>
511    
512     </body>
513     </section>
514     <section>
515 plasmaroo 1.17 <title>Bootloader Configuration</title>
516 swift 1.1 <body>
517    
518     <p>
519 plasmaroo 1.17 To set up genkernel to work with your bootloader, three or four changes should
520 neysx 1.20 be applied to the bootloader's configuration file:
521 swift 1.1 </p>
522    
523     <ol>
524 neysx 1.23 <li>
525     Add <c>root=/dev/ram0</c> and <c>init=/linuxrc</c> to the kernel parameters
526     passed to the kernel image.
527     </li>
528     <li>
529     Add <c>real_root=/dev/hda3</c>, for example, to the kernel parameters
530     passed to the kernel image, if <path>/dev/hda3</path> contains your root
531     partition.
532     </li>
533     <li>
534     If you are using bootsplash, add a suitable mode line such as
535     <c>vga=0x317</c> to the parameters passed to the kernel and also add
536     <c>splash=verbose</c> or <c>splash=silent</c> depending on the verboseness
537     you require from your bootloader.
538     </li>
539     <li>
540     Add the initrd information as required by the bootloader. Consult the <uri
541 cam 1.24 link="/doc/en/handbook/handbook-x86.xml?part=1&amp;chap=10">Bootloader
542 neysx 1.23 Configuration Chapter</uri> of the Gentoo Handbook for details on how to
543     make your bootloader initrd-aware.
544 swift 1.1 </li>
545     </ol>
546    
547     </body>
548     </section>
549 plasmaroo 1.17 </chapter>
550    
551     <chapter>
552     <title>Configuration Options</title>
553 swift 1.9 <section>
554 plasmaroo 1.17 <title>Editing /etc/genkernel.conf</title>
555 swift 1.9 <body>
556    
557     <p>
558 plasmaroo 1.17 Passing flags to genkernel from the command line can be cumbersome, especially
559     if you have about a dozen flags:
560     </p>
561    
562     <pre caption="Running genkernel (overloaded with flags)">
563 neysx 1.23 # <i>genkernel --debuglevel=5 --no-color --no-mrproper --clean --gensplash \
564     --kerneldir=/path/to/alternate/kernel/sources --install --menuconfig \
565     --kernel-config=/path/to/preferred/configfile --save-config --mountboot all</i>
566 plasmaroo 1.17 </pre>
567    
568 neysx 1.23 <p>
569     Fortunately, there is a configuration file where most of the basic options can
570     be set (or changed) as necessary. What follows is a rundown of the more
571 plasmaroo 1.17 relevant options:
572     </p>
573    
574     <ul>
575 neysx 1.23 <li>
576     <b>MENUCONFIG=<c>[yes|no]</c></b>: This option is equivalent to the
577     <c>--menuconfig</c> flag used by genkernel, which in turn uses the <c>make
578     menuconfig</c> command to invoke a command-line based kernel configuration
579     utility. To invoke the utility automatically during kernel configuration
580     via this script, set this option to 'yes' here; otherwise, choose 'no'.
581     </li>
582     <li>
583     <b>CLEAN=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent to
584     the <c>--clean</c> flag used by genkernel, and invokes the <c>make
585     clean</c> command to remove all object files and dependencies from the
586     kernel's source tree. Setting this option to 'no' creates a cascade effect
587     &#8212; it is equivalent to genkernel's <c>--no-clean</c> flag, which
588     disables the <c>make clean</c> command and implies genkernel's
589     <c>--no-mrproper</c> flag &#8212; essentially nullifying the <c>make
590     mrproper</c> command.
591     </li>
592     <li>
593     <b>MRPROPER=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent
594     to <c>--mrproper</c> flag used by genkernel, and invokes the <c>make
595     mrproper</c> command, which purges the kernel source tree of any
596     configuration files. Selecting 'no' here is equivalent to genkernel's
597     <c>--no-mrproper</c> flag, which disables the <c>make mrproper</c> command.
598     </li>
599     <li>
600     <b>MOUNTBOOT=<c>[yes|no]</c></b>: Setting this option to 'yes' is
601     equivalent to the <c>--mountboot</c> flag, and automatically mounts the
602     <path>/boot/</path> directory (if needed) at compile time. If the
603     <path>/boot/</path> directory is on a separate partition, consider enabling
604     this option; it will make for one less (essential) step to remember later.
605     </li>
606     <li>
607     <b>SAVE_CONFIG=<c>[yes|no]</c></b>: After configuring the kernel, the
608     selected options are stored as <path>.config</path> in the kernel source
609     tree. This script may be overwritten during the next kernel compilation, or
610     even purged from the kernel source tree. Choosing 'yes' here is equivalent
611     to the <c>--save-config</c> flag, and stores all options selected during
612     kernel configuration as a script in the <path>/etc/kernels/</path>
613     directory. Choosing 'no' preserves the <e>status quo</e>.
614     </li>
615     <li>
616     <b>USECOLOR=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent
617     to the <c>--color</c> flag, which colors genkernel's output to ease
618     debugging (when needed.)
619     </li>
620     <li>
621     <b>DEBUGLEVEL=<c>[0|1|2|3|4|5]</c></b>: This option is for adjusting the
622     verbosity of the output produced by genkernel — setting this option to '0'
623     with <c>--debuglevel=0</c> will suppress all output produced by genkernel;
624     setting this option to '5' with <c>--debuglevel=5</c> provides the user
625     with all output produced by genkernel.
626     </li>
627 plasmaroo 1.17 </ul>
628    
629     <p>
630     By choosing the appropriate options in <path>/etc/genkernel.conf</path>, you
631     can halve the number of flags passed to genkernel from the command line:
632     </p>
633    
634     <pre caption="Running genkernel (with flags), after employing genkernel.conf">
635 cam 1.24 # <i>genkernel --gensplash --kerneldir=/path/to/alternate/kernel/sources \
636 neysx 1.23 --kernel-config=/path/to/preferred/configfile --install all</i>
637 plasmaroo 1.17 </pre>
638    
639     <p>
640     Identical results are obtained from both approaches, but the latter has most of
641     the options stored in a script that can be modified at a later date.
642 swift 1.9 </p>
643    
644     </body>
645     </section>
646 swift 1.1 </chapter>
647    
648     <chapter>
649 plasmaroo 1.17 <title>Network-Booting with genkernel</title>
650 swift 1.1 <section>
651 plasmaroo 1.17 <title>Network Booting from an Installation CD</title>
652     <body>
653    
654     <p>
655     The genkernel utility can build kernel and initrd images that provide support
656 cam 1.24 for network booting, or <e>netboot</e>ing. With any luck, you should be able
657 plasmaroo 1.17 to netboot any recent computer into the environment provided by the
658     Installation CD.
659     </p>
660    
661     <p>
662     The magic lies in genkernel's linuxrc script: it will try to <e>netmount</e>
663     the Installation CD using NFS. From there, <e>the init scripts</e> of the
664     Installation CD can take over, as if the CD was present locally.
665     </p>
666    
667     </body>
668     </section>
669     <section>
670     <title>Building Kernel and Initrd Images with Support for Netbooting</title>
671 swift 1.1 <body>
672    
673     <p>
674 plasmaroo 1.17 To enable support for netbooting, include the following options while
675     configuring the kernel:
676 swift 1.1 </p>
677    
678 plasmaroo 1.17 <warn>
679     Support for netbooting with genkernel is experimental and may contain bugs.
680     </warn>
681    
682     <p>
683     First, the kernel image must include the drivers for your Network Interface
684 plasmaroo 1.18 Cards (NIC). Normally, drivers for such devices will be compiled as modules.
685 alin 1.21 However, it is essential (for netbooting) that you have such drivers compiled
686 plasmaroo 1.18 directly into the kernel image and <b>not</b> as modules.
687 plasmaroo 1.17 </p>
688    
689     <pre caption="Configuring a 2.6.x series kernel to support your NIC driver">
690     Device Drivers --->
691     Networking Support --->
692 cam 1.24 Ethernet (10 or 100Mbit) --->
693     [*] Ethernet (10 or 100Mbit)
694 plasmaroo 1.17 &lt;*&gt; the driver for your network card
695 alin 1.21 <comment>(Be sure to select &lt;*&gt; and not &lt;M&gt;)</comment>
696 plasmaroo 1.17 </pre>
697    
698     <p>
699 neysx 1.23 Secondly, we suggest that you enable <c>IP: kernel level autoconfiguration</c>
700     and the <c>IP: DHCP support</c> options. This avoids an unnecessary layer of
701     complexity since the IP address and the NFS path to the Installation CD can be
702     configured on a DHCP server. Of course, this means the kernel command line
703     will remain constant for any machine — which is very important for
704     <e>etherbooting</e>.
705 plasmaroo 1.17 </p>
706    
707     <pre caption="Configuring a 2.6.x series kernel to support DHCP">
708     Device Drivers --->
709     Networking Support --->
710 cam 1.24 Networking options
711 plasmaroo 1.17 [*] TCP/IP networking--->
712     [*] IP: kernel level autoconfiguration
713     [*] IP: DHCP support
714     <comment>(These options tell the kernel to send a DHCP request at bootup.)</comment>
715     </pre>
716    
717     <p>
718     Additionally, you should enable SquashFS because most modern Gentoo
719     Installation CDs require it. Support for SquashFS is not included with the
720     generic kernel source tree. To enable SquashFS, apply the necessary patches to
721     the generic kernel source or install <c>gentoo-sources</c>.
722     </p>
723    
724     <pre caption="Configuring the kernel to support SquashFS">
725 cam 1.24 File systems--->
726 plasmaroo 1.17 Miscellaneous filesystems --->
727     [*] SquashFS 2.X - Squashed file system support
728     </pre>
729    
730     <p>
731     Once the compilation process is completed, create a compressed <e>tarball</e>
732     (tar.gz) that contains the kernel's modules. This step is only necessary if
733     your kernel version does not match the kernel image version on the Installation
734     CD.
735     </p>
736    
737     <pre caption="Creating a compressed tarball containing the kernel modules">
738 neysx 1.23 <comment>(Create a tar.gz containing all the modules)</comment>
739     # <i>cd /</i>
740     # <i> tar -cf /tmp/modules-X.Y.Z.tar.gz /lib/modules/X.Y.Z/</i>
741 plasmaroo 1.17 </pre>
742    
743     <p>
744     Depending on your network boot mechanism, you will need to do some of the
745     following steps:
746     </p>
747    
748     <pre caption="Creating a boot image">
749 neysx 1.23 <comment>(Create an etherboot image)</comment>
750     # <i>emerge mknbi</i>
751     # <i>cd /boot</i>
752     # <i>mkelf-linux -params="root=/dev/ram0 init=/linuxrc ip=dhcp" kernel... initrd... > etherboot.img</i>
753    
754     <comment>(Create a OpenBoot / SPARC64 TFTP image)</comment>
755     # <i>emerge sparc-utils</i>
756     # <i>cd /boot</i>
757     # <i>elftoaout kernel... -o kernel.aout</i>
758     # <i>piggyback64 kernel.aout System.map-... initrd-...</i>
759     # <i>mv kernel.aout openboot.img</i> <comment>(This is the boot image)</comment>
760 plasmaroo 1.17
761 neysx 1.23 <comment>(PXE does not need any more steps, the kernel and initrd can be used as is)</comment>
762 plasmaroo 1.17 </pre>
763    
764     <p>
765     Finally, copy this kernel to your TFTP server. The details are
766     architecture-dependent and are beyond the scope of this guide. Please refer to
767     the documentation for your platform.
768     </p>
769    
770     </body>
771     </section>
772     <section>
773     <title>NFS Setup</title>
774     <body>
775    
776 swift 1.1 <p>
777 plasmaroo 1.17 To setup a NFS share that contains the Installation CD, use the loop device to
778     mount the ISO image and then copy the contents of the CD into the NFS share. As
779     a nice extra, genkernel's initrd scripts will extract all tar.gz files located
780     in the <path>/nfs/livecd/add/</path> directory. All you have to do here is copy
781     the <c>modules-X.Y.Z.tar.gz</c> archive to the <path>/nfs/livecd/add/</path>
782     directory.
783 swift 1.1 </p>
784    
785 plasmaroo 1.17 <pre caption="Preparing the NFS share">
786 neysx 1.23 <comment>(This assumes that /nfs/livecd is a exported NFS share)</comment>
787     # <i>mount /mnt/cdrom /tmp/gentoo-livecd.iso -o loop</i>
788     # <i>cp -p /mnt/cdrom /nfs/livecd</i>
789     # <i>umount /mnt/cdrom</i>
790    
791     <comment>(Copy the modules.tar.gz into /add)</comment>
792     # <i>mkdir /nfs/livecd/add</i>
793     # <i>cp /tmp/modules-X.Y.Z.tar.gz /nfs/livecd/add</i>
794 plasmaroo 1.17 </pre>
795    
796 swift 1.1 </body>
797     </section>
798     <section>
799 plasmaroo 1.17 <title>DHCP Setup</title>
800 swift 1.1 <body>
801    
802 plasmaroo 1.17 <p>
803 neysx 1.23 The netboot images will ask your DHCP server for an IP as well as a root-path
804 cam 1.24 parameter. Both can be specified per host using a MAC address to identify
805 neysx 1.23 machines:
806 plasmaroo 1.17 </p>
807    
808     <pre caption="Sample client dhcpd.conf setup">
809     ...
810    
811     host netbootableMachine {
812     hardware ethernet 11:22:33:44:55:66;
813     fixed-address 192.168.1.10;
814     option root-path "192.168.1.2:/nfs/livecd";
815     }
816     <comment># Here, 192.168.1.2 is the NFS server
817     # While 192.168.1.10 will be the IP address of the netbooted machine</comment>
818     ...
819     </pre>
820 swift 1.1
821     </body>
822     </section>
823     <section>
824 plasmaroo 1.17 <title>Netbooting Instructions</title>
825 swift 1.1 <body>
826    
827 plasmaroo 1.17 <p>
828 neysx 1.23 Netbooting itself is again very platform-specific. The important part is to
829     specify the <c>ip=dhcp</c> and <c>init=/linuxrc</c> parameters on the kernel
830     command line, as this will bring up the network interface and tell the initrd
831     scripts to mount the Installation CD via NFS. Here are some platform-specific
832     tips:
833 plasmaroo 1.17 </p>
834    
835     <pre caption="Netbooting Instructions">
836     <comment># Etherboot - insert the etherboot disk into the drive and reboot
837     # The kernel command line was specified when the image was constructed</comment>
838    
839 neysx 1.23 <comment># Sparc64 - Hit Stop-A at the boot prompt</comment>
840 plasmaroo 1.17 ok boot net ip=dhcp init=/linuxrc
841    
842 neysx 1.23 <comment># PXE - Setup pxelinux (part of syslinux),
843     then create a pxelinux.cfg/default along the lines of:</comment>
844 plasmaroo 1.17
845     DEFAULT gentoo
846     TIMEOUT 40
847     PROMPT 1
848    
849     LABEL gentoo
850 neysx 1.23 KERNEL kernel-X.Y.Z
851     APPEND initrd=initrd-X.Y.Z root=/dev/ram0 init=/linuxrc ip=dhcp
852 plasmaroo 1.17 </pre>
853    
854     </body>
855     </section>
856     </chapter>
857    
858     <chapter>
859     <title>Conclusion</title>
860     <section>
861     <title>To Automate or not to Automate?</title>
862     <body>
863 swift 1.1
864 plasmaroo 1.17 <p>
865     The purpose of genkernel is to provide an (easier) alternative to the
866 plasmaroo 1.18 time-tested approach to kernel compilation. As always, you are free to decide
867     on whether or not you want to automate the kernel compilation process.
868 plasmaroo 1.17 </p>
869 swift 1.1
870     </body>
871     </section>
872     </chapter>
873 plasmaroo 1.17
874 swift 1.1 </guide>

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