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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.
     _________________________________________________________________
   
   Table of Contents
   [1]About the kerneld mini-HOWTO
          
        [2]Credits
                
   [3]What is kerneld?
          
        [4]Why do I want to use it ?
        [5]Where can I pick up the necessary pieces ?
                
   [6]How do I set it up?
          
        [7]Trying out kerneld
                
   [8]How does kerneld know what module to load?
          
        [9]Block devices
        [10]Character devices
        [11]Network devices
        [12]Binary formats
        [13]Line disciplines (slip, cslip and ppp)
        [14]Network protocol families (IPX, AppleTalk, AX.25)
        [15]File systems
                
   [16]Devices requiring special configuration
          
        [17]char-major-10 : Mice, watchdogs and randomness
        [18]Loading SCSI drivers: The scsi_hostadapter entry
        [19]When loading a module isn't enough: The post-install entry
                
   [20]Spying on kerneld
   [21]Special kerneld uses
   [22]Common problems and things that make you wonder
          
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 [23]the Linux Documentation Project
     _________________________________________________________________
   
Credits

   This document is based on an original HTML version 1.7 dated July 19,
   1997 by Henrik Storner <[24]storner@osiris.ping.dk> and was revised
   and translated to DocBook DTD by Gary Lawrence Murphy
   <[25]garym@teledyn.com> 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
   <[26]kerneld-howto@linuxdoc.org>. Your comments, encouragement and
   suggestions are welcome and appreciated, and help ensure this guide
   remains current and accurate.
     _________________________________________________________________
   
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.
     _________________________________________________________________
   
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.
     _________________________________________________________________
   
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 Linux FTP archive sites including:
   
     * [27]Kernel.Org Archive
     * [28]Metalab Linux Archive
     * [29]TSX-11 at MIT
       
   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.
     _________________________________________________________________
   
How do I set it up?

   First get the necessary parts: A suitable kernel and the latest
   modules package. Then you should install the module utilities as per
   the instructions included in the package. Pretty simple: Just unpack
   the sources and run make install. This compiles and installs the
   following programs in /sbin: genksysm, insmod, lsmod, modprobe, depmod
   and kerneld. I recommend you add some lines to your startup-scripts to
   do some necessary setup whenever you boot Linux. Add the following
   lines to your /etc/rc.d/rc.S file (if you are running Slackware), or
   to /etc/rc.d/rc.sysinit if you are running SysVinit, i.e. Debian,
   Corel, RedHat, Mandrake or Caldera:
        # Start kerneld - this should happen very early in the
        # boot process, certainly BEFORE you run fsck on filesystems
        # that might need to have disk drivers autoloaded
        if [ -x /sbin/kerneld ]
        then
                /sbin/kerneld
        fi

        # Your standard fsck commands go here
        # And you mount command to mount the root fs read-write

        # Update kernel-module dependencies file
        # Your root-fs MUST be mounted read-write by now
        if [ -x /sbin/depmod ]
        then
                /sbin/depmod -a
        fi

   These commands may already be installed in your SysV init scripts. The
   first part starts kerneld itself. The second calls depmod -a at
   startup to build a list of all available modules and analyzes their
   inter-dependencies. The depmod map then tells kerneld if one module
   needs to have another loaded before it will itself load.
   
     Note: Recent versions of kerneld have an option to link with the
     GNU gdbm library, libgdbm. If you enable this when building the
     module utilities, kerneld will not start if libgdbm is not
     available which may well be the case if you have /usr on a separate
     partition and start kerneld before /usr is mounted. The recommended
     solution is to move /usr/lib/libgdbm to /lib, or to link kerneld
     statically.
     
   Next, unpack the kernel sources, configure and build a kernel to your
   liking. If you have never done this before, you should definitely read
   the README file at the top level of the Linux sources. When you run
   make xconfig to configure the kernel, you should pay attention to some
   questions that appear early on:
  Enable loadable module support (CONFIG_MODULES) [Y/n/?] Y

   You need to select the loadable module support, or there will be no
   modules for kerneld to load! Just say Yes.
  Kernel daemon support (CONFIG_KERNELD) [Y/n/?] Y

   This, of course, is also necessary. Then, a lot of the things in the
   kernel can be built as modules - you will see questions like
  Normal floppy disk support (CONFIG_BLK_DEV_FD) [M/n/y/?]

   where you can answer with an M for "Module". Generally, only the
   drivers necessary for you to boot up your system should be built into
   the kernel; the rest can be built as modules.
   
   Essential drivers
   
   Essential drivers required to boot your system must be compiled into
   the core kernel and cannot be loaded as modules. Typically this will
   include the hard-disk driver and the driver for the root filesystem.
   If you have a dual-boot machine and rely on files found in the foreign
   partition, you must also compile support for that filesystem into the
   core kernel.
   
   When you have gone through the make config, compile and install the
   new kernel and the modules with make dep clean bzlilo modules
   modules_install.
   
   Phew.
   
     Compiling a Kernel Image: The make zImage command will stop short
     of installing a kernel and will leave the new kernel image in the
     file arch/i386/boot/zImage. To use this image, you will need to
     copy it to where you keep your boot-image and install it manually
     with LILO.
     
     For more information about configuring, building and installing
     your own kernel, check out the Kernel-HOWTO posted regularly to
     comp.os.linux.answers, and available from [30]the Linux
     Documentation Project and its mirrors.
     _________________________________________________________________
   
Trying out kerneld

   Now reboot with the new kernel. When the system comes back up, you can
   run ps ax, and you should see a line for kerneld:
    PID TTY STAT  TIME COMMAND
     59  ?  S     0:01 /sbin/kerneld

   One of the nice things with kerneld is that once you have the kernel
   and the daemon installed, very little setup is needed. For a start,
   try using one of the drivers that you built as a module; it is more
   likely than not that it will work without further configuration. If I
   build the floppy driver as a module, I could put a DOS floppy in the
   drive and type
  osiris:~ $ mdir a:
   Volume in drive A has no label
   Volume Serial Number is 2E2B-1102
   Directory for A:/

  binuti~1 gz       1942 02-14-1996  11:35a binutils-2.6.0.6-2.6.0.7.diff.gz
  libc-5~1 gz      24747 02-14-1996  11:35a libc-5.3.4-5.3.5.diff.gz
          2 file(s)        26689 bytes

   The floppy driver works! It gets loaded automatically by kerneld when
   I try to use the floppy disk.
   
   To see that the floppy module is indeed loaded, you can run
   /sbin/lsmod to list all currently loaded modules:
  osiris:~ $ /sbin/lsmod
  Module:        #pages:  Used by:
  floppy            11    0 (autoclean)

   The "(autoclean)" means that the module will automatically be removed
   by kerneld when it has not been used for more than one minute. So the
   11 pages of memory (= 44kB, one page is 4 kB) will only be used while
   I access the floppy drive - if I don't use the floppy for more than a
   minute, they are freed. Quite nice, if you are short of memory for
   your applications!
     _________________________________________________________________
   
How does kerneld know what module to load?

   Although kerneld comes with builtin knowledge about the most common
   types of modules, there are situations where kerneld will not know how
   to handle a request from the kernel. This is the case with things like
   CD-ROM drivers or network drivers, where there are more than one
   possible module that can be loaded.
   
   The requests that the kerneld daemon gets from the kernel is for one
   of the following items:
   
     * a block-device driver
     * a character-device driver
     * a binary format
     * a tty line discipline
     * a filesystem
     * a network device
     * a network service (e.g. rarp)
     * a network protocol (e.g. IPX)
       
   The kerneld determines what module should be loaded by scanning the
   configuration file /etc/conf.modules[31][1]. There are two kinds of
   entries in this file: Paths where the module-files are located, and
   aliases assigning the module to be loaded for a given service. If you
   don't have this file already, you could create it by running
  /sbin/modprobe -c | grep -v '^path' /etc/conf.modules

   If you want to add yet another path directive to the default paths,
   you must include all the default paths as well, since a path directive
   in /etc/conf.modules will replaceall the ones that modprobe knows by
   default!
   
   Normally you don't want to add any paths by your own, since the
   built-in set should take care of all normal setups (and then some...),
   I promise!
   
   On the other hand, if you just want to add an alias or an option
   directive, your new entries in /etc/conf.modules will be added to the
   ones that modprobe already knows. If you should redefine an alias or
   an option, your new entries in /etc/conf.modules will override the
   built-in ones.
     _________________________________________________________________
   
Block devices

   If you run /sbin/modprobe -c, you will get a listing of the modules
   that kerneld knows about, and what requests they correspond to. For
   instance, the request that ends up loading the floppy driver is for
   the block-device that has major number 2:
  osiris:~ $ /sbin/modprobe -c | grep floppy
  alias block-major-2 floppy

   Why block-major-2 ? Because the floppy devices /dev/fd* use major
   device 2 and are block devices:
  osiris:~ $ ls -l /dev/fd0 /dev/fd1
  brw-rw-rw-   1 root     root       2,   0 Mar  3  1995 /dev/fd0
  brw-r--r--   1 root     root       2,   1 Mar  3  1995 /dev/fd1
     _________________________________________________________________
   
Character devices

   Character devices are dealt with in a similar way. E.g. the ftape
   floppy tape driver sits on major-device 27:
  osiris:~ $ ls -lL /dev/ftape
  crw-rw----   1 root     disk      27,   0 Jul 18  1994 /dev/ftape

   However, kerneld does not by default know about the ftape driver - it
   is not listed in the output from /sbin/modprobe -c. So to setup
   kerneld to load the ftape driver, I must add a line to the kerneld
   configuration file, /etc/conf.modules:
  alias char-major-27 ftape
     _________________________________________________________________
   
Network devices

   You can also use the device name instead of the char-major-xxx or
   block-major-yyy setup. This is especially useful for network drivers.
   For example, a driver for an ne2000 netcard acting as eth0 would be
   loaded with
  alias eth0 ne

   If you need to pass some options to the driver, for example to tell
   the module about what IRQ the netcard is using, you must add an
   "options" line:
  options ne irq=5

   This will cause kerneld to load the NE2000 driver with the command
  /sbin/modprobe ne irq=5

   Of course, the actual options available are specific to the module you
   are loading.
     _________________________________________________________________
   
Binary formats

   Binary formats are handled in a similar way. Whenever you try to run a
   program that the kernel does not know how to load, kerneld gets a
   request for binfmt-xxx, where xxx is a number determined from the
   first few bytes of the executable. So, the kerneld configuration to
   support loading the binfmt_aout module for ZMAGIC (a.out) executables
   is
  alias binfmt-267 binfmt_aout

   Since the magic number for ZMAGIC files is 267, if you check
   /etc/magic, you will see the number 0413; keep in mind that /etc/magic
   uses octal numbers where kerneld uses decimal, and octal 413 = decimal
   267. There are actually three slightly different variants of a.out
   executables (NMAGIC, QMAGIC and ZMAGIC), so for full support of the
   binfmt_aout module we need
  alias binfmt-264 binfmt_aout  # pure executable (NMAGIC)
  alias binfmt-267 binfmt_aout  # demand-paged executable (ZMAGIC)
  alias binfmt-204 binfmt_aout  # demand-paged executable (QMAGIC)

   a.out, Java and iBCS binary formats are recognized automatically by
   kerneld, without any configuration.
     _________________________________________________________________
   
Line disciplines (slip, cslip and ppp)

   Line disciplines are requested with tty-ldisc-x, with x being usually
   1 (for SLIP) or 3 (for PPP). Both of these are known by kerneld
   automatically.
   
   Speaking of ppp, if you want kerneld to load the bsd_comp data
   compression module for ppp, then you must add the following two lines
   to your /etc/conf.modules:
  alias tty-ldisc-3 bsd_comp
  alias ppp0 bsd_comp
     _________________________________________________________________
   
Network protocol families (IPX, AppleTalk, AX.25)

   Some network protocols can be loaded as modules as well. The kernel
   asks kerneld for a protocol family (e.g. IPX) with a request for
   net-pf-X where X is a number indicating what family is wanted. E.g.
   net-pf-3 is AX.25, net-pf-4 is IPX and net-pf-5 is AppleTalk; These
   numbers are determined by the AF_AX25, AF_IPX etc. definitions in the
   linux source file include/linux/socket.h. So to autoload the IPX
   module, you would need an entry like this in /etc/conf.modules:
  alias net-pf-4 ipx

   See [32]Common Problems for information about how you can avoid some
   annoying boot-time messages related to undefined protocol families.
     _________________________________________________________________
   
File systems

   kerneld requests for filesystems are simply the name of the filesystem
   type. A common use of this would be to load the isofs module for
   CD-ROM filesystems, i.e. filesystems of type iso9660:
  alias iso9660 isofs
     _________________________________________________________________
   
Devices requiring special configuration

   Some devices require a bit of extra configuration beyond the normal
   aliasing of a device to a module.
   
     * Character devices on major number 10: [33]The miscellaneous
       devices
     * [34]SCSI devices
     * [35]Devices that require special initialization
     _________________________________________________________________
   
char-major-10 : Mice, watchdogs and randomness

   Hardware devices are usually identified through their major device
   numbers, e.g. ftape is char-major-27. However, if you look through the
   entries in /dev for char major 10, you will see that this is a bunch
   of very different devices, including
   
     * Mice of various sorts (bus mice, PS/2 mice)
     * Watchdog devices
     * The kernel random device
     * APM (Advanced Power Management) interface
       
   These devices are controlled by several different modules, not a
   single one, and therefore the kerneld configuration for these misc.
   devices use the major number and the minor number:
        alias char-major-10-1 psaux     # For PS/2 mouse
        alias char-major-10-130 wdt     # For WDT watchdog

   You need a kernel version 1.3.82 or later to use this; earlier
   versions do not pass the minor number to kerneld, making it impossible
   for kerneld to figure out which of the misc. device modules to load.
     _________________________________________________________________
   
Loading SCSI drivers: The scsi_hostadapter entry

   Drivers for SCSI devices consist of a driver for the SCSI host adapter
   (e.g. an Adaptec 1542), and a driver for the type of SCSI device you
   use, e.g. a hard disk, a CD-ROM or a tape-drive. All of these can be
   loaded as modules. However, when you want to access e.g. the CD-ROM
   drive that is connected to the Adaptec card, the kernel and kerneld
   only knows that it needs to load the sr_mod module in order to support
   SCSI CD-ROM's; it does not know what SCSI controller the CD-ROM is
   connected to, and hence does not know what module to load to support
   the SCSI controller.
   
   To resolve this, you can add an entry for the SCSI driver module to
   your /etc/conf.modules that tells kerneld which of the many possible
   SCSI controller modules it should load:
        alias scd0 sr_mod               # sr_mod for SCSI CD-ROM's ...
        alias scsi_hostadapter aha1542  # ... need the Adaptec driver

   This only works with kernel version 1.3.82 or later.
   
   This works if you have only one SCSI controller. If you have more than
   one, things become a little more difficult.
   
   In general, you cannot have kerneld load a driver for a SCSI host
   adapter, if a driver for another host adapter is already installed.
   You must either build both drivers into your kernel (not as modules),
   or load the modules manually.
   
     Tip: There is a way that you can have kerneld load multiple SCSI
     drivers. James Tsiao came up with this idea:
     
     You can easily have kerneld load the second scsi driver by setting
     up the dependency in your modules.dep by hand. You just need an
     entry like:
     
      /lib/modules/2.0.30/scsi/st.o: /lib/modules/2.0.30/scsi/aha1542.o

     To have kerneld load the aha1542.o before it loads st.o. My machine
     at home is set up almost exactly like the setup above, and it works
     fine for all my secondary scsi devices, including tape, cd-rom, and
     generic scsi devices. The drawback is that depmod -a can't
     autodetect these dependencies, so the user needs to add them by
     hand, and not run depmod -a on boot up. But once it is set up,
     kerneld will autoload the aha1542.o just fine.
     
   You should be aware, that this technique only works if you have
   different kinds of SCSI devices on the two controllers, for example,
   hard disks on one controller, and cd-rom drives, tapes or generic SCSI
   devices on another.
     _________________________________________________________________
   
When loading a module isn't enough: The post-install entry

   Sometimes, just loading the module is not enough to get things
   working. For instance, if you have your sound card compiled as a
   module, it is often convenient to set a certain volume level. Only
   problem is, the setting vanishes the next time the module is loaded.
   Here is a neat trick from Ben Galliart (<[36]bgallia@luc.edu>):
   
     The final solution required installing the [37]setmix package and
     then adding the following line to my /etc/conf.modules:
     
post-install sound /usr/local/bin/setmix -f /etc/volume.conf

   What this does is that after the sound module is loaded, kerneld runs
   the command indicated by the post-install sound entry. So the sound
   module gets configured with the command /usr/local/bin/setmix -f
   /etc/volume.conf.
   
   This may be useful for other modules as well, for example the lp
   module can be configured with the tunelp program by adding
        post-install lp tunelp options

   For kerneld to recognize these options, you will need a version of
   kerneld that is 1.3.69f or later.
   
     Note: An earlier version of this mini-HOWTO mentioned a pre-remove
     option, that might be used to run a command just before kerneld
     removed a module. However, this has never worked and its use is
     therefore discouraged - most likely, this option will disappear in
     a future kerneld release. The whole issue of module settings is
     undergoing some change at the moment, and may look different on
     your system by the time you read this.
     _________________________________________________________________
   
Spying on kerneld

   If you have tried everything, and just cannot figure out what the
   kernel is asking kerneld to do, there is a way of seeing the requests
   that kerneld receives, and hence to figure out what should go into
   /etc/conf.modules: The kdstat utility.
   
   This nifty little program comes with the modules-package, but it is
   not compiled or installed by default. To build it, go to the directory
   where you have the kerneld sources and type make kdstat. Then, to make
   kerneld display information about what it is doing, run kdstat debug
   and kerneld will start spewing messages on the console about what it
   is doing. If you then try and run the command that you want to use,
   you will see the kerneld requests; these can be put into
   /etc/conf.modules and aliased to the module needed to get the job
   done.
   
   To turn off the debugging, run /sbin/kdstat nodebug.
     _________________________________________________________________
   
Special kerneld uses

   I knew you would ask about how to setup the screen-saver module!
   
   The kerneld/GOODIES directory in modules package has a couple of
   kernel patches for screen-saver and console-beep support in kerneld;
   these are not yet part of the official kernel, so you will need to
   install the kernel-patches and rebuild the kernel.
   
   To install a patch, you use the patch command:
  cd /usr/src/linux
  patch -s -p1 /usr/src/modules-*/kerneld/GOODIES/blanker_patch

   Then rebuild and install the new kernel.
   
   When the screen-saver triggers, kerneld will run the command
   /sbin/screenblanker; this file may be anything you like, for example,
   a shell script that runs your favorite screen-saver.
   
   When the kernel wants to unblank the screen, it sends a SIGQUIT signal
   to the process running /sbin/screenblanker. Your shell script or
   screen-saver should trap this, and terminate. Remember to restore the
   screen to the original text mode!
     _________________________________________________________________
   
Common problems and things that make you wonder

   1. [38]Why do I get Cannot locate module for net-pf-X messages when I
          run /sbin/ifconfig?
          
   2. [39]After starting kerneld, my system slows to a crawl when I
          activate my ppp-connection
          
   3. [40]kerneld does not load my SCSI driver!
   4. [41]modprobe complains about gcc2_compiled being undefined
   5. [42]My sound driver keeps forgetting its settings for volume etc
   6. [43]DOSEMU needs some modules; how can I get kerneld to load those
          ?
          
   7. [44]Why do I get Ouch, kerneld timed out, message failed messages ?
   8. [45]Mount doesn't wait for kerneld to load the filesystem module
   9. [46]kerneld fails to load the ncpfs module
   10. [47]kerneld fails to load the smbfs module
   11. [48]I built everything as modules, and now my system cannot boot
          or kerneld fails to load the root filesystem module!
          
   12. [49]kerneld will not load at boot time; it complains about libgdbm
   13. [50]I get Cannot load module xxx but I just reconfigured my kernel
          without xxx support!
          
   14. [51]I rebuilt my kernel and modules, and still get messages about
          unresolved symbols when booting
          
   15. [52]I installed Linux 2.1/2.3 and now I cannot load any modules!
   16. [53]What about dial-on-demand networking?
          
   1. Why do I get Cannot locate module for net-pf-X messages when I run
   /sbin/ifconfig?
   
   Around kernel version 1.3.80, the networking code was changed to allow
   loading protocol families (e.g. IPX, AX.25 and AppleTalk) as modules.
   This caused the addition of a new kerneld request: net-pf-X, where X
   is a number identifying the protocol (see
   /usr/src/linux/include/linux/socket.h for the meaning of the various
   numbers). Unfortunately, ifconfig accidentally triggers these
   messages, so a lot of people get a couple of messages logged when the
   system boots and it runs ifconfig to setup the loopback device. The
   messages are harmless, and you can disable them by adding the lines
        alias net-pf-3 off      # Forget AX.25
        alias net-pf-4 off      # Forget IPX
        alias net-pf-5 off      # Forget AppleTalk

   to /etc/conf.modules. Of course, if you do use IPX as a module, you
   should not add a line to disable IPX.
   
   2. After starting kerneld, my system slows to a crawl when I activate
   my ppp-connection
   
   There have been a couple of reports of this. It seems to be an
   unfortunate interaction between kerneld and the tkPPP script that is
   used on some systems to setup and monitor the PPP connection. The
   script apparently runs loops while running ifconfig. This triggers
   kerneld, to look for the net-pf-X modules (see above), keeping the
   system load high and possibly pouring lots of Cannot locate module for
   net-pf-X messages into the system log. There is no known workaround,
   other than not use tkPPP, or change it to use some other way of
   monitoring the connection.
   
   3. kerneld does not load my SCSI driver!
   
   Add an entry for the SCSI hostadapter to your /etc/conf.modules. See
   the description of the [54]scsi_hostadapter entry above.
   
   4. modprobe complains about gcc2_compiled being undefined
   
   This is a bug in the module utilities, that show up only with binutils
   2.6.0.9 and later, and it is also documented in the release note for
   the binutils. So read that, or fetch an upgrade to the
   module-utilities that fix this bug.
   
   5. My sound driver keeps forgetting its settings for volume etc
   
   The settings for a module are stored inside the module itself when it
   is loaded. So when kerneld auto-unloads a module, any settings you
   have made are forgotten, and the next time the module loads it reverts
   to the default settings.
   
   You can tell kerneld to configure a module by running a program after
   the module has been auto-loaded. See [55]Pre/Post Install on the
   post-install entry.
   
   6. DOSEMU needs some modules; how can I get kerneld to load those ?
   
   You cannot. None of the dosemu versions, official or development
   versions, support loading the dosemu modules through kerneld. However,
   if you are running kernel 2.0.26 or later, you do not need the special
   dosemu modules any longer; just upgrade dosemu to 0.66.1 or higher.
   
   7. Why do I get Ouch, kerneld timed out, message failed messages ?
   
   When the kernel sends a request off to to kerneld, it expects to
   receive an acknowledgment back within one second. If kerneld does not
   send this acknowledgment, this message is logged. The request is
   retransmitted, and should get through eventually.
   
   This usually happens on systems with a very high load. Since kerneld
   is a user-mode process, it is scheduled just like any other process on
   the system. At times of high load, it may not get to run in time to
   send back the acknowledgment before the kernel times out.
   
   If this happens even when the load is light, try restarting kerneld.
   Kill the kerneld process, and start it again with the command
   /usr/sbin/kerneld. If the problem persists, you should mail a bug
   report to <[56]linux-kernel@vger.rutgers.edu>, but please make sure
   that your versions of the kernel, kerneld and the module utilities are
   up-to-date before posting about the problem. Check the requirements in
   linux/Documentation/Changes
   
   8. Mount doesn't wait for kerneld to load the filesystem module
   
   There has been a number of reports that the mount(8) command does not
   wait for kerneld to load the filesystem module. lsmod does show that
   kerneld loads the module, and if you repeat the mount command
   immediately it will succeed. This appears to be a bug in the
   module-utilities version 1.3.69f that affects some Debian users. It
   can be fixed by getting a later version of the module-utilities.
   
   9. kerneld fails to load the ncpfs module
   
   You need to compile the ncpfs utilities with -DHAVE_KERNELD. See the
   ncpfs Makefile.
   
   10. kerneld fails to load the smbfs module
   
   You are using an older version of the smbmount utilities. Get the
   latest version (0.10 or later) from [57]the SMBFS archive one TSX-11
   
   11. I built everything as modules, and now my system cannot boot or
   kerneld fails to load the root filesystem module!
   
   You cannot modularize everything: The kernel must have enough drivers
   built in for it to be able to mount your root filesystem, and run the
   necessary programs to start kerneld[58][2]. You cannot modularize
   
     * the driver for the hard disk where your root filesystem lives
     * the root filesystem driver itself
     * the binary format loader for init, kerneld and other programs
       
   12. kerneld will not load at boot time; it complains about libgdbm
   
   Newer versions of kerneld need the GNU dbm library, libgdbm.so, to
   run. Most installations have this file in /usr/lib, but you are
   probably starting kerneld before the /usr filesystem is mounted. One
   symptom of this is that kerneld will not start during boot-up (from
   your rc-scripts), but runs fine if you start it by hand after that
   system is up. The solution is to either move the kerneld startup to
   after your /usr is mounted, or move the gdbm library to your root
   filesystem, e.g. to /lib.
   
   13. I get Cannot load module xxx but I just reconfigured my kernel
   without xxx support!
   
   The Slackware installation (possibly others) builds a default
   /etc/rc.d/rc.modules which does an explicit modprobe on a variety of
   modules. Exactly which modules get modprobed depends on the original
   kernel's configuration. You have probably reconfigured your kernel to
   exclude one or more of the modules that is getting modprobed in
   rc.modules, thus, the error message(s). Update your rc.modules by
   commenting out any modules you no longer use, or remove the rc.modules
   entirely and let kerneld load the modules when they are needed.
   
   14. I rebuilt my kernel and modules, and still get messages about
   unresolved symbols when booting
   
   You probably reconfigured/rebuilt your kernel and excluded some
   modules. You've got some old modules that you no longer use hanging
   around in the /lib/modules directory. The easiest fix is to delete
   your /lib/modules/x.y.z directory and do a make modules_install from
   the kernel source directory again. Note that this problem only occurs
   when reconfiguring your kernel without changing versions. If you see
   this error when moving to a newer kernel version you've got some other
   problem.
   
   15. I installed Linux 2.1/2.3 and now I cannot load any modules!
   
   Odd numbered Linux are development kernels. As such, it should be
   expected that things break from time to time. One of the things that
   has changed significantly is the way modules are handled, and where
   the kernel and modules are loaded into memory.
   
   In brief, if you want to use modules with a development kernel, you
   must
   
     * read the Documentation/Changes file and see what packages need
       upgrading on your system
     * use the latest modutils package, available from [59]AlphaBits on
       Red Hat or the mirror site at [60]TSX-11
       
   I recommend using at least kernel 2.1.29, if you want to use modules
   with a 2.1 kernel.
   
   16. What about dial-on-demand networking?
   
   kerneld originally had some support for establishing dial-up network
   connections on demand; trying to send packets to a network without
   being connected would cause kerneld to run the /sbin/request_route
   script to setup a PPP or SLIP connection.
   
   This turned out to be a bad idea. Alan Cox of Linux networking fame
   wrote on the linux-kernel mailing list
   
     The request-route stuff is obsolete, broken and not required [...]
     Its also removed from 2.1.x trees.
     
   Instead of using the request-route script and kerneld, I highly
   recommend Eric Schenk's [61]diald package to manage your demand
   dialing.
   
  Notes
  
   [62][1]
   
   Some distributions call this file modules.conf
   [63][2]
   
   Actually, this is not true. Late 1.3.x and all 2.x kernels support the
   use of an initial ram-disk that is loaded by LILO or LOADLIN; it is
   possible to load modules from this disk very early in the boot
   process. How to do it is described in the
   linux/Documentation/initrd.txt file that comes with the kernel
   source-files.

References

   1. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN26
   2. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#CREDITS
   3. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#INTRODUCTION
   4. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#WHY
   5. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#WHERE
   6. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SETUP
   7. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#TESTING
   8. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#CONFIGURATION
   9. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#BLOCKDEV
  10. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#CHARDEV
  11. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#ETH0
  12. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#BINFMT
  13. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#LDISC
  14. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#NET-PF
  15. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#FS
  16. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SPECIAL-DEVS
  17. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#MISCDEVS
  18. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SCSIDEVS
  19. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#PRE-POST
  20. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SPYING
  21. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#GOODIES
  22. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#COMMONPROBLEMS
  23. http://www.linuxdoc.org/
  24. mailto:storner@osiris.ping.dk
  25. mailto:garym@teledyn.com
  26. mailto:kerneld-howto@linuxdoc.org
  27. ftp://ftp.kernel.org/pub/linux/kernel/
  28. ftp://metalab.unc.edu/pub/Linux/kernel/
  29. ftp://tsx-11.mit.edu/pub/linux/sources/system/
  30. http://www.linuxdoc.org/
  31. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#FTN.AEN192
  32. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#COMMONPROBLEMS
  33. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#MISCDEVS
  34. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SCSIDEVS
  35. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#PRE-POST
  36. mailto:bgallia@luc.edu
  37. ftp://sunsite.unc.edu/pub/Linux/apps/sound/mixers/
  38. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN381
  39. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN398
  40. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN410
  41. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN418
  42. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN424
  43. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN432
  44. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN437
  45. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN449
  46. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN455
  47. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN464
  48. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN472
  49. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN488
  50. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN498
  51. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN507
  52. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN516
  53. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN532
  54. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#SCSIDEVS
  55. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#PRE-POST
  56. mailto:linux-kernel@vger.rutgers.edu
  57. ftp://tsx-11.mit.edu/pub/linux/filesystems/smbfs/
  58. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#FTN.AEN477
  59. ftp://ftp.redhat.com/pub/alphabits/
  60. ftp://tsx-11.mit.edu/pub/linux/packages/alphabits/
  61. http://www.dna.lth.se/~erics/diald.html
  62. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN192
  63. file://localhost/export/sunsite/users/gferg/howto/00_Kerneld.html#AEN477





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