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1 cam 1.24 <?xml version="1.0" encoding="UTF-8"?>
2 swift 1.37 <!-- $Header: /var/cvsroot/gentoo/xml/htdocs/doc/en/genkernel.xml,v 1.36 2011/01/21 06:24:57 nightmorph Exp $ -->
3 swift 1.1 <!DOCTYPE guide SYSTEM "/dtd/guide.dtd">
4    
5 nightmorph 1.35 <guide>
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 plasmaroo 1.17 <!-- folajimi@speakeasy.net -->
12     <author title="Contributor">
13     Jimi Ayodele
14     </author>
15     <!-- thseiler@gmail.com -->
16     <author title="NFS Support">
17     Thomas Seiler
18     </author>
19 nightmorph 1.31 <author title="Editor">
20     <mail link="nightmorph"/>
21     </author>
22 nightmorph 1.32 <author title="Contributor">
23     <mail link="sping"/>
24     </author>
25 plasmaroo 1.17
26 swift 1.1 <abstract>
27 plasmaroo 1.17 This guide intends to provide a reference of all the functions provided by
28 cam 1.24 genkernel.
29 swift 1.1 </abstract>
30    
31 nightmorph 1.32 <!-- The content of this document is licensed under the CC-BY-SA license -->
32     <!-- See http://creativecommons.org/licenses/by-sa/2.5 -->
33 plasmaroo 1.4 <license/>
34    
35 swift 1.37 <version>7</version>
36     <date>2011-09-03</date>
37 swift 1.1
38     <chapter>
39     <title>Introduction</title>
40     <section>
41 plasmaroo 1.17 <title>Rationale</title>
42 swift 1.1 <body>
43    
44     <p>
45 nightmorph 1.35 For users who don't want to manually compile their kernels, genkernel is a tool
46     to automate this process. It can help you create a kernel image akin to those
47 plasmaroo 1.17 available on Gentoo Installation CDs, which are designed to auto-detect the
48     hardware configuration of your system. Some users may also be interested in
49     using genkernel for hardware requiring initialization and a working kernel
50 nightmorph 1.35 before the system starts up.
51 swift 1.1 </p>
52    
53     </body>
54     </section>
55     <section>
56 plasmaroo 1.17 <title>Target Audience</title>
57 swift 1.1 <body>
58    
59     <p>
60 plasmaroo 1.17 If you are either uncertain about how to compile a kernel, or are just
61     unfamiliar with your hardware configuration, genkernel is a very handy tool.
62     It is designed to take the pain out of the kernel compiling process, and
63     supports most hardware by default.
64 swift 1.1 </p>
65    
66     <p>
67 plasmaroo 1.17 However, if you know what drivers are required by your system, you may be able
68     to further reduce the time taken to compile the kernel. This is possible since
69     you can direct genkernel to only build drivers relevant to your hardware.
70     Oftentimes, the number of drivers required by your system will be fewer
71     (implying a shorter kernel compilation time) than the default configuration
72     provides.
73 swift 1.1 </p>
74    
75     </body>
76     </section>
77     <section>
78 plasmaroo 1.17 <title>Installing genkernel</title>
79 swift 1.1 <body>
80    
81     <p>
82 nightmorph 1.35 To obtain genkernel, run <c>emerge genkernel</c> from the command line. Consult
83     <c>genkernel --help</c> for help on how to use the version of genkernel
84     installed on your system.
85 swift 1.1 </p>
86 cam 1.24
87 swift 1.1 </body>
88     </section>
89 plasmaroo 1.17 </chapter>
90    
91     <chapter>
92     <title>Working with genkernel</title>
93 swift 1.1 <section>
94 plasmaroo 1.17 <title>How to use genkernel</title>
95 swift 1.1 <body>
96    
97     <p>
98 plasmaroo 1.17 Although there are several ways to run genkernel, the least-intrusive approach
99     is provided by <c>genkernel all</c>. Here, a generic configuration which works
100     well for most systems is used. As was mentioned earlier, this approach is not
101     without drawbacks; most of the modules created are useless to the average user
102     and may increase compile time. Below is an illustration of a more efficient
103     approach, achieved by passing certain flags to genkernel as root:
104     </p>
105    
106     <pre caption="Running genkernel (with flags)">
107 nightmorph 1.31 # <i>genkernel --splash --no-install --no-clean --menuconfig all</i>
108 plasmaroo 1.17 </pre>
109    
110     <p>
111 nightmorph 1.31 The above operation causes genkernel to create a framebuffer splash-enabled
112     kernel (<c>--splash</c>) that will have to be manually installed
113 plasmaroo 1.17 (<c>--no-install</c>). While preparing the kernel source tree, genkernel will
114     refrain from cleaning out any preexisting object files present in the source
115     tree (<c>--no-clean</c>). A menu-driven kernel configuration utility will be
116     displayed that allows the user to select which modules will be built for the
117     system (<c>--menuconfig</c>).
118     </p>
119    
120     <p>
121     There are other flags which alter the result provided by genkernel. For
122 nightmorph 1.33 instance, replacing <c>--no-install</c> with the <c>--install</c> flag allows
123 plasmaroo 1.17 genkernel to automatically install the new kernel in the <path>/boot</path>
124 nightmorph 1.35 directory, and will create symlinks for you if <c>--symlink</c> is specified.
125     Using the <c>--mountboot</c> flag allows genkernel to mount your
126 plasmaroo 1.17 <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 nightmorph 1.35 The rest of this chapter examines the functionality of various flags,
141     configuration variables, and actions available for genkernel. For a more
142 nightmorph 1.36 complete list, please refer to <c>man genkernel</c> and the comments in
143 nightmorph 1.35 <path>/etc/genkernel.conf</path>. Some of the flags have variants which
144     perform a converse operation. The converse variants carry the <b><c>no-</c></b>
145     prefix, and their effects are enclosed within the square brackets, [].
146 swift 1.1 </p>
147    
148     </body>
149     </section>
150     <section>
151 plasmaroo 1.17 <title>Configuration Flags</title>
152 swift 1.1 <body>
153    
154     <p>
155 plasmaroo 1.17 The configuration flags listed below exist to help you decide what features
156     should be enabled or disabled in the kernel prior to compilation. You can even
157     choose whether or not the configuration file created in the process should be
158     saved. The following are the primary configuration flags:
159 swift 1.1 </p>
160    
161     <ul>
162 neysx 1.23 <li>
163     <b>--<c>no-</c>menuconfig</b>: Activates <e>[or deactivates]</e> the
164     <c>make menuconfig</c> command (which invokes an interactive, menu-based
165     kernel configuration utility), before building the kernel.
166     </li>
167     <li>
168     <b>--gconfig</b>: Provides a kernel configuration utility which depends on
169     the GTK+ libraries. The advantage of this option is that most users find it
170     easier and clearer to configure the kernel using this tool, since it relies
171     on the X-windowing system. The disadvantage of this option is that you
172     <b>need</b> the X-windowing system to use it, so it will not work on the
173     command line.
174     </li>
175     <li>
176     <b>--xconfig</b>: Provides a kernel configuration utility which depends on
177     the QT libraries. The advantage of this option is that most users find it
178     easier and clearer to configure the kernel using this tool, since it relies
179     on the X-windowing system. The disadvantage of this option is that you
180     <b>need</b> the X-windowing system to use it, so it will not work on the
181     command line.
182     </li>
183     <li>
184 cam 1.25 <b>--<c>no-</c>save-config</b>: Saves <e>[or does not save]</e> the kernel
185 neysx 1.23 configuration to a file in the <path>/etc/kernels/</path> directory for
186     later use.
187     </li>
188 swift 1.1 </ul>
189    
190     </body>
191     </section>
192     <section>
193 plasmaroo 1.17 <title>Compilation Flags</title>
194 swift 1.1 <body>
195    
196     <p>
197 plasmaroo 1.17 The following flags usually take effect during the actual compilation:
198 swift 1.1 </p>
199    
200     <ul>
201     <li>
202 neysx 1.23 <b>--kerneldir=<path>/path/to/sources/</path></b>: Specifies an alternative
203     kernel source location, rather than the default
204 plasmaroo 1.17 <path>/usr/src/linux/</path> location.
205 swift 1.1 </li>
206     <li>
207 plasmaroo 1.17 <b>--kernel-config=<path>/path/to/config-file</path></b>: Specifies what
208     alternative kernel configuration will be used, rather than the default
209     <path>/path/to/sources/.config</path> file.
210 swift 1.1 </li>
211     <li>
212 neysx 1.23 <b>--module-prefix=<path>/path/to/prefix-directory/</path></b>: Specifies a
213     prefix to the directory where kernel modules will be installed (default
214 plasmaroo 1.17 path is the <path>/lib/modules/</path> directory.)
215 swift 1.1 </li>
216     </ul>
217    
218     <ul>
219     <li>
220 neysx 1.23 <b>--<c>no-</c>clean</b>: Activates <e>[or deactivates]</e> the <c>make
221     clean</c> command before compiling your kernel. The <c>make clean</c>
222     command removes all object files and dependencies from the kernel's source
223     tree.
224 swift 1.1 </li>
225     <li>
226 neysx 1.23 <b>--<c>no-</c>mrproper</b>: Activates <e>[or deactivates]</e> the <c>make
227     mrproper</c> command before kernel compilation. Like the <c>make clean</c>
228     command, <c>make mrproper</c> removes all object files and dependencies
229     from the kernel's source tree. However, any previous configuration files
230     (in <path>/path/to/sources/.config</path> or
231     <path>/path/to/sources/.config.old</path>) will <b>also</b> be purged from
232     the kernel's source tree.
233 swift 1.1 </li>
234     <li>
235 plasmaroo 1.17 <b>--oldconfig</b>: Issues the <c>make oldconfig</c> command, which
236 neysx 1.23 attempts to collect configuration information for the system's architecture
237     from a generic script in <path>/usr/share/genkernel/</path>. This is a
238     non-interactive process; no user input is entertained. Also, if
239 plasmaroo 1.17 <c>--oldconfig</c> is used in conjunction with <c>--clean</c>, the latter
240 neysx 1.23 flag is negated, resulting in the activation of the <c>--no-clean</c> flag.
241 swift 1.1 </li>
242 plasmaroo 1.17 </ul>
243    
244     <ul>
245 neysx 1.23 <li>
246     <b>--callback="<c>echo hello</c>"</b>: Calls the specified arguments
247     (<c>echo hello</c>, in this case) after the kernel and the relevant modules
248     have been built, but before building the initrd image. This may be useful
249     if you want to install external modules in the initrd image by emerging the
250     relevant item(s) with the callback feature, and then redefining a genkernel
251     module group.
252     </li>
253 swift 1.1 </ul>
254    
255     <ul>
256 neysx 1.23 <li>
257     <b>--<c>no-</c>install</b>: Activates <e>[or deactivates]</e> the <c>make
258     install</c> command, which installs your new kernel image, configuration
259     file, initrd image and system map onto your mounted boot partition. Any
260     compiled modules will be installed as well.
261     </li>
262     <li>
263 nightmorph 1.35 <b>--no-ramdisk-modules</b>: Refrains from copying any modules to the
264 neysx 1.23 genkernel-created initrd image. This flag is an exception to the rule about
265     the <c>no-</c> prefix; omission of this prefix creates an invalid genkernel
266     flag.
267     </li>
268     <li>
269 nightmorph 1.32 <b>--all-ramdisk-modules</b>: Copies all available modules to the
270     genkernel-created initrd image.
271     </li>
272     <li>
273 neysx 1.23 <b>--genzimage</b>: Creates the initrd image, prior to the kernel image.
274     (This hack currently applies only to PPC Pegasos systems.)
275     </li>
276 swift 1.1 </ul>
277    
278     </body>
279     </section>
280     <section>
281 plasmaroo 1.17 <title>Compiler Flags</title>
282 swift 1.1 <body>
283    
284     <p>
285 plasmaroo 1.17 The following flags are supported by genkernel, and are passed to the relevant
286     applications while the kernel is being assembled. These flags affect the
287     <e>compiler</e> used for the kernel compilation process, albeit at a much lower
288     level.
289 swift 1.1 </p>
290    
291     <ul>
292 neysx 1.23 <li>
293     <b>--kernel-cc=<c>someCompiler</c></b>: Specifies the compiler employed
294     during the kernel compilation process.
295     </li>
296     <li>
297     <b>--kernel-ld=<c>someLinker</c></b>: Specifies the linker employed during
298     the kernel compilation process.
299     </li>
300     <li>
301     <b>--kernel-as=<c>someAssembler</c></b>: Specifies the assembler employed
302     during the kernel compilation process.
303     </li>
304     <li>
305     <b>--kernel-make=<c>someMake</c></b>: Specifies an alternative to the
306     <e>GNU make</e> utility employed during the kernel compilation process.
307     </li>
308 plasmaroo 1.17 </ul>
309    
310     <ul>
311 neysx 1.23 <li>
312     <b>--utils-cc=<c>someCompiler</c></b>: Specifies the compiler employed
313     during the compilation of support utilities.
314     </li>
315     <li>
316     <b>--utils-ld=<c>someLinker</c></b>: Specifies the linker employed during
317     the compilation of support utilities.
318     </li>
319     <li>
320     <b>--utils-as=<c>someAssembler</c></b>: Specifies the assembler employed
321     during the compilation of support utilities.
322     </li>
323     <li>
324     <b>--utils-make=<c>someMake</c></b>: Specifies an alternative to the <e>GNU
325     make</e> utility employed during the compilation of support utilities.
326     </li>
327 plasmaroo 1.17 </ul>
328    
329     <ul>
330 neysx 1.23 <li>
331     <b>--makeopts=<c>-jX</c></b>: Specifies the number of concurrent threads
332     that the make utility can implement while the kernel (and utilities) are
333     being compiled. The variable <b>'X'</b> is a number obtained by adding one
334     (1) to the number of CPUs used by the system. So, for a system with one
335     CPU, the appropriate flag is <c>-j2</c>; a system with two CPUs will use
336     the <c>-j3</c> flag, and so on. <e>(A system with one processor that
337 cam 1.25 supports Hyper-Threading&trade; (HT) Technology can use the
338     </e><c>-j3</c><e> flag, provided Symmetric Multi-Processing (SMP) support is
339     enabled in the kernel.)</e>
340 neysx 1.23 </li>
341 swift 1.1 </ul>
342    
343 plasmaroo 1.17 </body>
344     </section>
345     <section>
346     <title>Debugging Flags</title>
347     <body>
348    
349     <p>
350 rane 1.27 The use of debugging flags during the kernel compilation process controls the
351 plasmaroo 1.17 amount of information reported, as well as the presentation of said data.
352     </p>
353    
354 swift 1.1 <ul>
355 neysx 1.23 <li>
356 nightmorph 1.32 <b>--loglevel=<c>verblevel</c></b>: Controls the level of verbosity for
357 neysx 1.23 information provided by genkernel. The variable <c>verblevel</c> is an
358     integer between 0 and 5. The level '0' represents minimal output, while '5'
359     provides as much information as possible about genkernel's activities
360     during the kernel compilation process.
361     </li>
362     <li>
363 nightmorph 1.32 <b>--logfile=<path>/path/to/outputfile</path></b>: Ignores the value set
364     by the <c>--loglevel</c> argument, and sends <b>all</b> debugging data
365 neysx 1.23 produced by genkernel to the specified output file, which is located at
366     <path>/var/log/genkernel.log</path> by default.
367     </li>
368     <li>
369 cam 1.25 <b>--no-color</b>: Activates <e>[or deactivates]</e> colored output of
370     debugging information (reported by genkernel) using escape sequences.
371 neysx 1.23 </li>
372 swift 1.1 </ul>
373    
374 plasmaroo 1.17 </body>
375     </section>
376    
377     <section>
378     <title>Initialization Flags</title>
379     <body>
380    
381     <p>
382     The flags here are used to create certain effects during system startup. Some
383     of these flags are primarily for aesthetics, while others may be essential for
384     enabling certain features on the system.
385     </p>
386    
387 swift 1.1 <ul>
388 neysx 1.23 <li>
389 nightmorph 1.31 <b>--<c>no-</c>splash</b>: Activates <e>[or deactivates]</e> support for
390     <uri link="http://fbsplash.berlios.de/wiki/doku.php">framebuffer
391     splash</uri> support in the genkernel-built initrd image. To override the
392     default theme used by fbsplash, use <b>--splash=<c>PreferredTheme</c></b>
393     (where <c>PreferredTheme</c> is the title of one of the directories inside
394     the <path>/etc/splash/</path> directory.
395 neysx 1.23 </li>
396     <li>
397 nightmorph 1.31 <b>--splash-res=<c>PreferredResolution</c></b>: This flag allows you to
398 neysx 1.23 select which splash screen resolutions will be supported in the initrd
399     during the start-up of the system. This is useful for two reasons: First,
400 nightmorph 1.31 you are able to select only the splash screen resolution(s) relevant to your
401     system. Second, you avoid the unnecessary increase in the disk space
402 neysx 1.23 required by initrd (since the initrd does not have to support resolutions
403 nightmorph 1.31 that are irrelevant for your system configuration.) However, you may want to
404     omit this flag if the kernel is being compiled for an Installation CD; this
405     allows splash support for all possible resolutions.
406 neysx 1.23 </li>
407     <li>
408     <b>--do-keymap-auto</b>: Force keymap selection during the boot sequence.
409     </li>
410     <li>
411 nightmorph 1.36 <b>--lvm</b>: Includes support for storage using via <uri
412 neysx 1.23 link="http://sources.redhat.com/lvm2/">Logical Volume Management</uri>
413     (LVM2) from <e>static</e> binaries, if available to the system. Relevant
414     (static) LVM2 binaries are compiled if they are unavailable. Be sure to
415     install the lvm2 package on your system with <c>emerge lvm2</c> before
416     enabling this flag, and review the <uri link="/doc/en/lvm2.xml">Gentoo LVM2
417     Installation</uri> guide.
418     </li>
419     <li>
420     <b>--dmraid</b>: Includes support for <uri
421     link="http://people.redhat.com/~heinzm/sw/dmraid/readme">DMRAID</uri>; the
422     utility which creates RAID mappings using the kernel device-mapper
423     subsystem. DMRAID discovers, activates, deactivates and displays properties
424     of software RAID sets (ATARAID, for example) and contained DOS partitions.
425     </li>
426     <li>
427 nightmorph 1.29 <b>--luks</b>: Includes support for <uri
428     link="http://luks.endorphin.org/">Linux Unified Key Setup</uri> or LUKS.
429     This will allow you to use a device encrypted by LUKS which contains the
430     root filesystem. On the bootloader, you then set that encrypted device as
431     the value of crypt_root (and real_root shall be the unencrypted device LUKS
432     creates).
433     </li>
434 nightmorph 1.35 <li>
435     <b>--disklabel</b>: Adds support for disk label and UUID support to your
436     initrd.
437     </li>
438     <li>
439     <b>--iscsi</b>: Adds support for iSCSI to your initrd.
440     </li>
441     <li>
442     <b>--multipath</b>: Adds support for <uri
443     link="/doc/en/multipath.xml">Multipath</uri> to your initrd.
444     </li>
445 nightmorph 1.29 <li>
446 neysx 1.23 <b>--linuxrc=/path/to/your/linuxrc</b>: Specifies a user-created
447 cam 1.25 <e>linuxrc</e> &mdash; a script that is initialized during the start-up
448     stage of the kernel, prior to the actual boot process. (A default linuxrc
449     script should be in the <path>/usr/share/genkernel/</path> directory.) This
450     script allows you to boot into a small, modularized kernel and load the
451     drivers that are needed (as modules) by the system.
452 neysx 1.23 </li>
453     <li>
454     <b>--cachedir=/path/to/alt/dir/</b>: Overrides the default cache location
455     used while compiling the kernel.
456     </li>
457     <li>
458     <b>--tempdir=/path/to/new/tempdir/</b>: Specifies the location of the
459     temporary directory used by genkernel while compiling the kernel.
460     </li>
461     <li>
462     <b>--unionfs</b>: Includes support for the <uri
463     link="http://www.fsl.cs.sunysb.edu/project-unionfs.html">Unification File
464     System</uri> in the initrd image.
465     </li>
466 swift 1.1 </ul>
467    
468     </body>
469     </section>
470     <section>
471 plasmaroo 1.17 <title>Miscellaneous Flags</title>
472 swift 1.1 <body>
473    
474     <p>
475 plasmaroo 1.17 The assortment of flags listed below are supported by genkernel, but do not fit
476     neatly into any of the other categories:
477 swift 1.1 </p>
478    
479     <ul>
480 neysx 1.23 <li>
481     <b>--mountboot</b>: Detects whether or not the <path>/boot/</path>
482     directory needs to be mounted on a separate partition. It will check
483     <path>/etc/fstab</path> script for instructions on how to mount the boot
484     partition on a file system (if needed).
485     </li>
486     <li>
487     <b>--kernname=<c>NickName</c></b>: Allows you to modify the name of the
488     kernel and initrd images in the <path>/boot/</path> directory, so that the
489     images produced are kernel-<c>NickName</c>-version and
490     initramfs-<c>NickName</c>-version.
491     </li>
492 swift 1.1 </ul>
493    
494     </body>
495     </section>
496     <section>
497 plasmaroo 1.17 <title>Possible Actions</title>
498 swift 1.1 <body>
499    
500     <p>
501 plasmaroo 1.17 An action tells genkernel what to build. Currently, the following actions are
502     supported:
503 swift 1.1 </p>
504    
505 plasmaroo 1.17 <ul>
506 cam 1.25 <li>
507     <c>all</c>: Builds all stages &mdash; the initrd, kernel image and modules.
508     </li>
509 nightmorph 1.33 <li><c>bzImage</c>: Only builds the kernel image</li>
510 nightmorph 1.34 <li><c>kernel</c>: Only builds the kernel image and modules</li>
511 nightmorph 1.33 <li><c>initramfs</c>: Only builds the initramfs/ramdisk image</li>
512     <li><c>ramdisk</c>: Only builds the initramfs/ramdisk image</li>
513 plasmaroo 1.17 </ul>
514 swift 1.1
515     <p>
516 nightmorph 1.34 The first action, <c>all</c>, is recommended for most users since it builds the
517 plasmaroo 1.17 stages required for a functional kernel. Remember, an <e>action</e> simply
518     tells genkernel what to <e>build</e>, not <e>install</e>.
519 swift 1.1 </p>
520    
521     </body>
522     </section>
523     <section>
524 plasmaroo 1.17 <title>Bootloader Configuration</title>
525 swift 1.1 <body>
526    
527     <p>
528 plasmaroo 1.17 To set up genkernel to work with your bootloader, three or four changes should
529 neysx 1.20 be applied to the bootloader's configuration file:
530 swift 1.1 </p>
531    
532     <ol>
533 neysx 1.23 <li>
534 nightmorph 1.35 Add <c>real_root=/dev/sda3</c>, for example, to the kernel parameters
535     passed to the kernel image, if <path>/dev/sda3</path> contains your root
536 neysx 1.23 partition.
537     </li>
538     <li>
539 nightmorph 1.31 If you are using splash, add a suitable mode line such as <c>vga=0x317</c>
540     to the parameters passed to the kernel and also add <c>splash=verbose</c> or
541     <c>splash=silent</c> depending on the verboseness you require from your
542     bootloader.
543 neysx 1.23 </li>
544     <li>
545     Add the initrd information as required by the bootloader. Consult the <uri
546 cam 1.24 link="/doc/en/handbook/handbook-x86.xml?part=1&amp;chap=10">Bootloader
547 neysx 1.23 Configuration Chapter</uri> of the Gentoo Handbook for details on how to
548     make your bootloader initrd-aware.
549 swift 1.1 </li>
550     </ol>
551    
552     </body>
553     </section>
554 plasmaroo 1.17 </chapter>
555    
556     <chapter>
557     <title>Configuration Options</title>
558 swift 1.9 <section>
559 plasmaroo 1.17 <title>Editing /etc/genkernel.conf</title>
560 swift 1.9 <body>
561    
562     <p>
563 plasmaroo 1.17 Passing flags to genkernel from the command line can be cumbersome, especially
564     if you have about a dozen flags:
565     </p>
566    
567     <pre caption="Running genkernel (overloaded with flags)">
568 nightmorph 1.32 # <i>genkernel --loglevel=5 --no-color --no-mrproper --clean --splash \
569 neysx 1.23 --kerneldir=/path/to/alternate/kernel/sources --install --menuconfig \
570     --kernel-config=/path/to/preferred/configfile --save-config --mountboot all</i>
571 plasmaroo 1.17 </pre>
572    
573 neysx 1.23 <p>
574     Fortunately, there is a configuration file where most of the basic options can
575 nightmorph 1.35 be set (or changed) as necessary: <path>/etc/genkernel.conf</path>. What follows
576     is a rundown of the more relevant options:
577 plasmaroo 1.17 </p>
578    
579     <ul>
580 neysx 1.23 <li>
581     <b>MENUCONFIG=<c>[yes|no]</c></b>: This option is equivalent to the
582     <c>--menuconfig</c> flag used by genkernel, which in turn uses the <c>make
583     menuconfig</c> command to invoke a command-line based kernel configuration
584     utility. To invoke the utility automatically during kernel configuration
585     via this script, set this option to 'yes' here; otherwise, choose 'no'.
586     </li>
587     <li>
588     <b>CLEAN=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent to
589     the <c>--clean</c> flag used by genkernel, and invokes the <c>make
590     clean</c> command to remove all object files and dependencies from the
591     kernel's source tree. Setting this option to 'no' creates a cascade effect
592     &#8212; it is equivalent to genkernel's <c>--no-clean</c> flag, which
593     disables the <c>make clean</c> command and implies genkernel's
594 cam 1.25 <c>--no-mrproper</c> flag &mdash; essentially nullifying the <c>make
595 neysx 1.23 mrproper</c> command.
596     </li>
597     <li>
598     <b>MRPROPER=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent
599     to <c>--mrproper</c> flag used by genkernel, and invokes the <c>make
600     mrproper</c> command, which purges the kernel source tree of any
601     configuration files. Selecting 'no' here is equivalent to genkernel's
602     <c>--no-mrproper</c> flag, which disables the <c>make mrproper</c> command.
603     </li>
604     <li>
605     <b>MOUNTBOOT=<c>[yes|no]</c></b>: Setting this option to 'yes' is
606     equivalent to the <c>--mountboot</c> flag, and automatically mounts the
607     <path>/boot/</path> directory (if needed) at compile time. If the
608     <path>/boot/</path> directory is on a separate partition, consider enabling
609     this option; it will make for one less (essential) step to remember later.
610     </li>
611     <li>
612     <b>SAVE_CONFIG=<c>[yes|no]</c></b>: After configuring the kernel, the
613     selected options are stored as <path>.config</path> in the kernel source
614     tree. This script may be overwritten during the next kernel compilation, or
615     even purged from the kernel source tree. Choosing 'yes' here is equivalent
616     to the <c>--save-config</c> flag, and stores all options selected during
617     kernel configuration as a script in the <path>/etc/kernels/</path>
618     directory. Choosing 'no' preserves the <e>status quo</e>.
619     </li>
620     <li>
621     <b>USECOLOR=<c>[yes|no]</c></b>: Setting this option to 'yes' is equivalent
622     to the <c>--color</c> flag, which colors genkernel's output to ease
623     debugging (when needed.)
624     </li>
625     <li>
626 nightmorph 1.32 <b>LOGLEVEL=<c>[0|1|2|3|4|5]</c></b>: This option is for adjusting the
627 cam 1.25 verbosity of the output produced by genkernel &mdash; setting this option to
628 nightmorph 1.32 '0' with <c>--loglevel=0</c> will suppress all output produced by
629     genkernel; setting this option to '5' with <c>--loglevel=5</c> provides
630 cam 1.25 the user with all output produced by genkernel.
631 neysx 1.23 </li>
632 plasmaroo 1.17 </ul>
633    
634 nightmorph 1.35 <note>
635     More options are described in <path>/etc/genkernel.conf</path>.
636     </note>
637    
638 plasmaroo 1.17 <p>
639     By choosing the appropriate options in <path>/etc/genkernel.conf</path>, you
640     can halve the number of flags passed to genkernel from the command line:
641     </p>
642    
643     <pre caption="Running genkernel (with flags), after employing genkernel.conf">
644 nightmorph 1.31 # <i>genkernel --splash --kerneldir=/path/to/alternate/kernel/sources \
645 neysx 1.23 --kernel-config=/path/to/preferred/configfile --install all</i>
646 plasmaroo 1.17 </pre>
647    
648     <p>
649     Identical results are obtained from both approaches, but the latter has most of
650     the options stored in a script that can be modified at a later date.
651 swift 1.9 </p>
652    
653     </body>
654     </section>
655 swift 1.1 </chapter>
656    
657     <chapter>
658 plasmaroo 1.17 <title>Network-Booting with genkernel</title>
659 swift 1.1 <section>
660 plasmaroo 1.17 <title>Network Booting from an Installation CD</title>
661     <body>
662    
663     <p>
664     The genkernel utility can build kernel and initrd images that provide support
665 cam 1.24 for network booting, or <e>netboot</e>ing. With any luck, you should be able
666 plasmaroo 1.17 to netboot any recent computer into the environment provided by the
667     Installation CD.
668     </p>
669    
670     <p>
671     The magic lies in genkernel's linuxrc script: it will try to <e>netmount</e>
672     the Installation CD using NFS. From there, <e>the init scripts</e> of the
673     Installation CD can take over, as if the CD was present locally.
674     </p>
675    
676     </body>
677     </section>
678     <section>
679     <title>Building Kernel and Initrd Images with Support for Netbooting</title>
680 swift 1.1 <body>
681    
682     <p>
683 plasmaroo 1.17 To enable support for netbooting, include the following options while
684     configuring the kernel:
685 swift 1.1 </p>
686    
687 plasmaroo 1.17 <warn>
688     Support for netbooting with genkernel is experimental and may contain bugs.
689     </warn>
690    
691     <p>
692     First, the kernel image must include the drivers for your Network Interface
693 plasmaroo 1.18 Cards (NIC). Normally, drivers for such devices will be compiled as modules.
694 alin 1.21 However, it is essential (for netbooting) that you have such drivers compiled
695 plasmaroo 1.18 directly into the kernel image and <b>not</b> as modules.
696 plasmaroo 1.17 </p>
697    
698     <pre caption="Configuring a 2.6.x series kernel to support your NIC driver">
699     Device Drivers --->
700     Networking Support --->
701 cam 1.24 Ethernet (10 or 100Mbit) --->
702     [*] Ethernet (10 or 100Mbit)
703 plasmaroo 1.17 &lt;*&gt; the driver for your network card
704 alin 1.21 <comment>(Be sure to select &lt;*&gt; and not &lt;M&gt;)</comment>
705 plasmaroo 1.17 </pre>
706    
707     <p>
708 neysx 1.23 Secondly, we suggest that you enable <c>IP: kernel level autoconfiguration</c>
709     and the <c>IP: DHCP support</c> options. This avoids an unnecessary layer of
710     complexity since the IP address and the NFS path to the Installation CD can be
711     configured on a DHCP server. Of course, this means the kernel command line
712 cam 1.25 will remain constant for any machine &mdash; which is very important for
713 neysx 1.23 <e>etherbooting</e>.
714 plasmaroo 1.17 </p>
715    
716     <pre caption="Configuring a 2.6.x series kernel to support DHCP">
717     Device Drivers --->
718     Networking Support --->
719 cam 1.24 Networking options
720 plasmaroo 1.17 [*] TCP/IP networking--->
721     [*] IP: kernel level autoconfiguration
722     [*] IP: DHCP support
723     <comment>(These options tell the kernel to send a DHCP request at bootup.)</comment>
724     </pre>
725    
726     <p>
727     Additionally, you should enable SquashFS because most modern Gentoo
728     Installation CDs require it. Support for SquashFS is not included with the
729     generic kernel source tree. To enable SquashFS, apply the necessary patches to
730     the generic kernel source or install <c>gentoo-sources</c>.
731     </p>
732    
733     <pre caption="Configuring the kernel to support SquashFS">
734 cam 1.24 File systems--->
735 plasmaroo 1.17 Miscellaneous filesystems --->
736     [*] SquashFS 2.X - Squashed file system support
737     </pre>
738    
739     <p>
740     Once the compilation process is completed, create a compressed <e>tarball</e>
741     (tar.gz) that contains the kernel's modules. This step is only necessary if
742     your kernel version does not match the kernel image version on the Installation
743     CD.
744     </p>
745    
746     <pre caption="Creating a compressed tarball containing the kernel modules">
747 neysx 1.23 <comment>(Create a tar.gz containing all the modules)</comment>
748     # <i>cd /</i>
749 cam 1.25 # <i>tar -cf /tmp/modules-X.Y.Z.tar.gz /lib/modules/X.Y.Z/</i>
750 plasmaroo 1.17 </pre>
751    
752     <p>
753     Depending on your network boot mechanism, you will need to do some of the
754     following steps:
755     </p>
756    
757     <pre caption="Creating a boot image">
758 neysx 1.23 <comment>(Create an etherboot image)</comment>
759     # <i>emerge mknbi</i>
760     # <i>cd /boot</i>
761     # <i>mkelf-linux -params="root=/dev/ram0 init=/linuxrc ip=dhcp" kernel... initrd... > etherboot.img</i>
762    
763     <comment>(Create a OpenBoot / SPARC64 TFTP image)</comment>
764     # <i>emerge sparc-utils</i>
765     # <i>cd /boot</i>
766     # <i>elftoaout kernel... -o kernel.aout</i>
767     # <i>piggyback64 kernel.aout System.map-... initrd-...</i>
768     # <i>mv kernel.aout openboot.img</i> <comment>(This is the boot image)</comment>
769 plasmaroo 1.17
770 neysx 1.23 <comment>(PXE does not need any more steps, the kernel and initrd can be used as is)</comment>
771 plasmaroo 1.17 </pre>
772    
773     <p>
774     Finally, copy this kernel to your TFTP server. The details are
775     architecture-dependent and are beyond the scope of this guide. Please refer to
776     the documentation for your platform.
777     </p>
778    
779     </body>
780     </section>
781     <section>
782     <title>NFS Setup</title>
783     <body>
784    
785 swift 1.1 <p>
786 plasmaroo 1.17 To setup a NFS share that contains the Installation CD, use the loop device to
787     mount the ISO image and then copy the contents of the CD into the NFS share. As
788     a nice extra, genkernel's initrd scripts will extract all tar.gz files located
789     in the <path>/nfs/livecd/add/</path> directory. All you have to do here is copy
790     the <c>modules-X.Y.Z.tar.gz</c> archive to the <path>/nfs/livecd/add/</path>
791     directory.
792 swift 1.1 </p>
793    
794 plasmaroo 1.17 <pre caption="Preparing the NFS share">
795 nightmorph 1.28 <comment>(This assumes that /nfs/livecd is an exported NFS share)</comment>
796 cam 1.25 # <i>mount /tmp/gentoo-livecd.iso /mnt/cdrom -o loop</i>
797 neysx 1.23 # <i>cp -p /mnt/cdrom /nfs/livecd</i>
798     # <i>umount /mnt/cdrom</i>
799    
800     <comment>(Copy the modules.tar.gz into /add)</comment>
801     # <i>mkdir /nfs/livecd/add</i>
802     # <i>cp /tmp/modules-X.Y.Z.tar.gz /nfs/livecd/add</i>
803 plasmaroo 1.17 </pre>
804    
805 swift 1.1 </body>
806     </section>
807     <section>
808 plasmaroo 1.17 <title>DHCP Setup</title>
809 swift 1.1 <body>
810    
811 plasmaroo 1.17 <p>
812 neysx 1.23 The netboot images will ask your DHCP server for an IP as well as a root-path
813 cam 1.24 parameter. Both can be specified per host using a MAC address to identify
814 neysx 1.23 machines:
815 plasmaroo 1.17 </p>
816    
817     <pre caption="Sample client dhcpd.conf setup">
818     ...
819    
820     host netbootableMachine {
821     hardware ethernet 11:22:33:44:55:66;
822     fixed-address 192.168.1.10;
823     option root-path "192.168.1.2:/nfs/livecd";
824     }
825     <comment># Here, 192.168.1.2 is the NFS server
826     # While 192.168.1.10 will be the IP address of the netbooted machine</comment>
827     ...
828     </pre>
829 swift 1.1
830     </body>
831     </section>
832     <section>
833 plasmaroo 1.17 <title>Netbooting Instructions</title>
834 swift 1.1 <body>
835    
836 plasmaroo 1.17 <p>
837 neysx 1.23 Netbooting itself is again very platform-specific. The important part is to
838     specify the <c>ip=dhcp</c> and <c>init=/linuxrc</c> parameters on the kernel
839     command line, as this will bring up the network interface and tell the initrd
840     scripts to mount the Installation CD via NFS. Here are some platform-specific
841     tips:
842 plasmaroo 1.17 </p>
843    
844     <pre caption="Netbooting Instructions">
845     <comment># Etherboot - insert the etherboot disk into the drive and reboot
846     # The kernel command line was specified when the image was constructed</comment>
847    
848 neysx 1.23 <comment># Sparc64 - Hit Stop-A at the boot prompt</comment>
849 plasmaroo 1.17 ok boot net ip=dhcp init=/linuxrc
850    
851 neysx 1.23 <comment># PXE - Setup pxelinux (part of syslinux),
852     then create a pxelinux.cfg/default along the lines of:</comment>
853 plasmaroo 1.17
854     DEFAULT gentoo
855     TIMEOUT 40
856     PROMPT 1
857    
858     LABEL gentoo
859 neysx 1.23 KERNEL kernel-X.Y.Z
860     APPEND initrd=initrd-X.Y.Z root=/dev/ram0 init=/linuxrc ip=dhcp
861 plasmaroo 1.17 </pre>
862    
863     </body>
864     </section>
865     </chapter>
866    
867     <chapter>
868     <title>Conclusion</title>
869     <section>
870     <title>To Automate or not to Automate?</title>
871     <body>
872 swift 1.1
873 plasmaroo 1.17 <p>
874     The purpose of genkernel is to provide an (easier) alternative to the
875 plasmaroo 1.18 time-tested approach to kernel compilation. As always, you are free to decide
876     on whether or not you want to automate the kernel compilation process.
877 plasmaroo 1.17 </p>
878 swift 1.1
879     </body>
880     </section>
881     </chapter>
882     </guide>

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