Kerneld(1), E-booki, How to EN

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Linux kerneld mini−HOWTO
Henrik Storner
kerneld−howto@linuxdoc.org
Copyright © 2000 by Linux Documentation Project
Revision History
Revision v2.0 22 May 2000
conversion from HTML to DocBook SGML.
Linux kerneld mini−HOWTO
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1. About the kerneld mini−HOWTO
This document explains how to install and use the automatic kernel module loader "kerneld". The latest
released version of this document can be found at
1.1. Credits
This document is based on an original HTML version 1.7 dated July 19, 1997 by Henrik Storner
<
and was revised and translated to DocBook DTD by Gary Lawrence
Murphy
<
>
May 20, 2000.
The following people have contributed to this mini−HOWTO at some point:
·
Bjorn Ekwall bj0rn@blox.se
·
Ben Galliart bgallia@luc.edu
Cedric Tefft cedric@earthling.net
· Brian Miller bmiller@netspace.net.au
·
James C. Tsiao jtsiao@madoka.jpl.nasa.gov
If you find errors in this document, please send email to
<
. Your
comments, encouragement and suggestions are welcome and appreciated, and help ensure this guide remains
current and accurate.
1. About the kerneld mini−HOWTO
1
·
  2. What is kerneld?
The kerneld feature was introduced during the 1.3 development kernels by Bjorn Ekwall. It allows kernel
modules such as device drivers, network drivers and filesystems to be loaded automatically when they are
needed, rather than having to do it manually with
modprobe
or
insmod
.
And for the more amusing aspects, although these are not (yet ?) integrated with the standard kernel:
· It can be setup to run a user−program instead of the default screen blanker, thus letting you use any
program as a screen−saver.
·
Similar to the screen−blanker support, you can also change the standard console beep into something
completely different.
kerneld consists of two components:
·
Support in the Linux kernel for sending requests to a daemon requesting a module for a certain task.
·
A user−space daemon that can figure out what modules must be loaded to fulfill the request from the
kernel.
Both components must be working for the kerneld support to function; it is not enough that only one or the
other has been setup.
2.1. Why do I want to use it ?
There are some good reasons for using kerneld. The ones I will mention are mine, others have other reasons.
· If you have to build kernels for several systems that only differ slightly − different kind of network
card, for instance − then you can build a single kernel and some modules, instead of having to build
individual kernels for each system.
Modules are easier for developers to test. You don't need to reboot the system to load and unload the
driver; this applies to all modules, not just kerneld−loaded ones.
· It cuts down on the kernel memory usage leaving more memory available for applications. Memory
used by the kernel is
never
swapped out, so if you have 100Kb worth of unused drivers compiled into
your kernel, they are simply wasting RAM.
Some of the things I use, the ftape floppy−tape driver, for instance, or iBCS, are only available as
modules, but I don't want to bother with loading and unloading them whenever I need them.
· People making Linux distributions don't have to build 284 different boot images: Each user loads the
drivers he needs for just his hardware. Most modern Linux distributions will detect your hardware
and will only load those modules actually required.
Of course, there are also reasons why you may not want to use it. If you prefer to have just one kernel image
file with all of your drivers built in, you are reading the wrong document.
2.2. Where can I pick up the necessary pieces ?
The support in the Linux kernel was introduced with Linux 1.3.57. If you have an earlier kernel version, you
will need to upgrade if you want the kerneld support. The current Linux kernel sources can be found at most
2. What is kerneld?
2
·
·
   Linux kerneld mini−HOWTO
Linux FTP archive sites including:
·
·
·
The user−space daemon is included with the modules package. These are normally available from the same
place as the kernel sources
Note:
If you want to try module−loading with the latest
development
kernels, you should use
the newer modutils package and not the modules. Always check the
Documentation/Changes
file in the kernel sources for the minimum required version
number for your kernel image. Also see about the problems with modules and 2.1 kernels.
2. What is kerneld?
3
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