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>Linux kerneld mini-HOWTO</TH
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><H1
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><A
NAME="SETUP"
>How do I set it up?</A
></H1
><P
>First get the necessary parts: A suitable kernel and the
latest <SPAN
CLASS="PRODUCTNAME"
>modules</SPAN
> package. Then you
should install the module utilities as per the instructions
included in the package. Pretty simple: Just unpack the sources
and run <B
CLASS="COMMAND"
>make install</B
>. This compiles and
installs the following programs in <TT
CLASS="FILENAME"
>/sbin</TT
>:
<B
CLASS="COMMAND"
>genksysm</B
>, <B
CLASS="COMMAND"
>insmod</B
>,
<B
CLASS="COMMAND"
>lsmod</B
>, <B
CLASS="COMMAND"
>modprobe</B
>,
<B
CLASS="COMMAND"
>depmod</B
> and <B
CLASS="COMMAND"
>kerneld</B
>. 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 <TT
CLASS="FILENAME"
>/etc/rc.d/rc.S</TT
> file (if you are
running Slackware), or to
<TT
CLASS="FILENAME"
>/etc/rc.d/rc.sysinit</TT
> if you are running
SysVinit, i.e. Debian, Corel, RedHat, Mandrake or Caldera:
</P
><TABLE
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><TR
><TD
><PRE
CLASS="PROGRAMLISTING"
> # 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</PRE
></TD
></TR
></TABLE
><P
>These commands may already be installed in your SysV init
scripts. The first part starts kerneld itself. The second calls
<B
CLASS="COMMAND"
>depmod -a</B
> 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. </P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
>Recent versions of kerneld have an option to link with the
GNU gdbm library, <SPAN
CLASS="PRODUCTNAME"
>libgdbm</SPAN
>. If you
enable this when building the module utilities,
<I
CLASS="EMPHASIS"
>kerneld will not start if libgdbm is not
available</I
> which may well be the case if you have
<TT
CLASS="FILENAME"
>/usr</TT
> on a separate partition and start
kerneld before <TT
CLASS="FILENAME"
>/usr</TT
> is mounted. The
recommended solution is to move
<TT
CLASS="FILENAME"
>/usr/lib/libgdbm</TT
> to
<TT
CLASS="FILENAME"
>/lib</TT
>, or to link kerneld
statically.</P
></BLOCKQUOTE
></DIV
><P
>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 <I
CLASS="EMPHASIS"
>make xconfig</I
>
to configure the kernel, you should pay attention to some
questions that appear early on: </P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> Enable loadable module support (CONFIG_MODULES) [Y/n/?] Y</PRE
></TD
></TR
></TABLE
><P
>You need to select the loadable module support, or there
will be no modules for kerneld to load! Just say Yes. </P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> Kernel daemon support (CONFIG_KERNELD) [Y/n/?] Y</PRE
></TD
></TR
></TABLE
><P
>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 </P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> Normal floppy disk support (CONFIG_BLK_DEV_FD) [M/n/y/?] </PRE
></TD
></TR
></TABLE
><P
>where you can answer with an <SPAN
CLASS="KEYSYM"
>M</SPAN
> for
<SPAN
CLASS="QUOTE"
>"Module"</SPAN
>. 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. </P
><DIV
CLASS="CAUTION"
><P
></P
><TABLE
CLASS="CAUTION"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Essential drivers</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
>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.</P
></TD
></TR
></TABLE
></DIV
><P
>When you have gone through the <B
CLASS="COMMAND"
>make
config</B
>, compile and install the new
kernel and the modules with <B
CLASS="COMMAND"
>make dep clean bzlilo
modules modules_install</B
>.</P
><P
>Phew. </P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Compiling a Kernel Image: </B
>The
<B
CLASS="COMMAND"
>make zImage</B
> command will stop short of
installing a kernel and will leave the new kernel image in the
file <TT
CLASS="FILENAME"
>arch/i386/boot/zImage</TT
>. To use this
image, you will
need to copy it to where you keep your boot-image and install it
manually with LILO. </P
><P
>For more information about configuring, building and
installing your own kernel, check out the Kernel-HOWTO posted
regularly to <TT
CLASS="FILENAME"
>comp.os.linux.answers</TT
>, and
available from <A
HREF="http://www.linuxdoc.org"
TARGET="_top"
>the Linux
Documentation Project</A
> and its mirrors.</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="TESTING"
>Trying out kerneld</A
></H2
><P
>Now reboot with the new kernel. When the system comes back
up, you can run <B
CLASS="COMMAND"
>ps ax</B
>, and you should see a
line for kerneld: </P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> PID TTY STAT TIME COMMAND
59 ? S 0:01 /sbin/kerneld</PRE
></TD
></TR
></TABLE
><P
>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</P
><TABLE
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WIDTH="100%"
><TR
><TD
><PRE
CLASS="SCREEN"
> 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</PRE
></TD
></TR
></TABLE
><P
>The floppy driver works! It gets loaded automatically
by kerneld when I try to use the floppy disk. </P
><P
>To see that the floppy module is indeed loaded, you can
run <B
CLASS="COMMAND"
>/sbin/lsmod</B
> to list all currently
loaded modules: </P
><TABLE
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><TR
><TD
><PRE
CLASS="SCREEN"
> osiris:~ $ /sbin/lsmod
Module: #pages: Used by:
floppy 11 0 (autoclean)</PRE
></TD
></TR
></TABLE
><P
>The <SPAN
CLASS="QUOTE"
>"(autoclean)"</SPAN
> 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! </P
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