The Linux Kernel HOWTO

Al Dev (Alavoor Vasudevan)

< alavoor[AT]yahoo.com >


v5.5, 22 April 2003


This is a detailed guide to kernel configuration, compilation, upgrades, and
troubleshooting for ix86-based systems. Can be useful for other architectures
as well. This document is kept small & simple, so that even non-technical
"home computer users" will be able to compile and run the Linux Kernel.

-----------------------------------------------------------------------------
Table of Contents
1. Introduction
2. Quick Steps - Kernel Compile
    2.1. Precautionary Preparations
    2.2. Minor Upgrading of Kernel
    2.3. For the Impatient
    2.4. Building New Kernel - Explanation of Steps
    2.5. Troubleshooting
    2.6. Post Kernel Building
   
   
3. Loadable Modules
    3.1. Installing the module utilities
    3.2. Modules distributed with the kernel
    3.3. Howto Install Just A Single Module ?
   
   
4. Cloning of Linux Kernels
5. Important questions and their answers
    5.1. What does the kernel do, anyway?
    5.2. Why would I want to upgrade my kernel?
    5.3. What kind of hardware do the newer kernels support?
    5.4. What version of gcc and libc do I need?
    5.5. What's a loadable module?
    5.6. How much disk space do I need?
    5.7. How long does it take?
   
   
6. Patching the kernel
    6.1. Applying a patch
    6.2. If something goes wrong
    6.3. Getting rid of the .orig files
    6.4. Other patches
   
   
7. Tips and tricks
    7.1. Redirecting output of the make or patch commands
    7.2. Conditional kernel install
    7.3. Kernel updates
   
   
8. Linux Kernel Textbooks and Documents
9. Kernel Files Information
    9.1. vmlinuz and vmlinux
    9.2. Bootloader Files
    9.3. Message File
    9.4. initrd.img
    9.5. bzImage
    9.6. module-info
    9.7. config
    9.8. grub
    9.9. System.map
   
   
10. Mount RPMs With FTPFS
    10.1. Using the ftpfs
    10.2. The ftpfs Commands
   
   
11. Other Formats of this Document
    11.1. Acrobat PDF format
    11.2. Convert Linuxdoc to Docbook format
    11.3. Convert to MS WinHelp format
    11.4. Reading various formats
   
   
12. Appendix A - Creating initrd.img file
    12.1. Using mkinitrd
    12.2. Kernel Docs
    12.3. Linuxman Book
   
   
13. Appendix B - Sample lilo.conf
14. Appendix C - GRUB Details And A Sample grub.conf
15. Appendix D - Post Kernel Building
16. Appendix E - Troubleshoot Common Mistakes
    16.1. Compiles OK but does not boot
    16.2. The System Hangs at LILO
    16.3. No init found
    16.4. Lot of Compile Errors
    16.5. The 'depmod' gives "Unresolved symbol error messages"
    16.6. Kernel Does Not Load Module - "Unresolved symbols" Error Messages
    16.7. Kernel fails to load a module
    16.8. Loadable modules
    16.9. See Docs
    16.10. make clean
    16.11. Huge or slow kernels
    16.12. The parallel port doesn't work/my printer doesn't work
    16.13. Kernel doesn't compile
    16.14. New version of the kernel doesn't seem to boot
    16.15. You forgot to run LILO, or system doesn't boot at all
    16.16. It says `warning: bdflush not running'
    16.17. I can't get my IDE/ATAPI CD-ROM drive to work
    16.18. It says weird things about obsolete routing requests
    16.19. ``Not a compressed kernel Image file''
    16.20. Problems with console terminal after upgrade to Linux v1.3.x
    16.21. Can't seem to compile things after kernel upgrade
    16.22. Increasing limits
   
   

1. Introduction

You compile Linux kernel for one of following reasons:

*You are doing kernel development
   
*You are adding a new hardware to machine
   
*You want to customize the kernel and do not want the default kernel
    shipped out to you.
   
*For Defence Industries or Military applications , you must read the
    kernel source code and compile with your own hands. No exceptions!! (U.S
    Dept of Defence compiles the Linux kernel before distributing the
    computers).
   
*Every country and every Government in the world compiles the kernel on
    site for security and integrity. Every Government/Corporation audits and
    verifies each and every line of the OS kernel source code before using
    the computer.
   
*Military Intelligence agencies around the world reads and compiles the
    Linux kernel source code. They know what each and every line of Linux
    kernel source code is doing!!
   
*If you compile the Linux kernel with your own hands, then it is as good
    as reading and verifying all the kernel source code!
   
*Each and every University in the world compiles the OS kernel before
    using any computer!
   
*For your education and knowledge of Linux kernel and ofcourse, just for
    fun!
   
*For very advanced scientific applications - you may need to do kernel
    compile
   
*It is an International Law (the U.N. laws) - "You cannot use a computer
    WITHOUT compiling the OS kernel with your own hands". If you disobey this
    law you will be "punished" with lot of computer problems!! You must
    compile the kernel with your own hands and not rely on someone else to do
    it for you!!
   
*It is Illegal, Unlawful, Felony and Fraud to use a computer without
    compiling the OS Kernel with your VERY OWN hands!
   
*In USA, all the corporations mandate compilation of OS kernel before
    using the computer and hence there is Linux, Linux & Linux everywhere in
    United States!
   
*And for many hundreds of reasons - too numerous to list!
   

Note: This document is kept small & simple, so that even non-technical "home
computer users" will be able to compile and run the Linux Kernel!
-----------------------------------------------------------------------------

2. Quick Steps - Kernel Compile

This section is written by Al Dev (alavoor[AT]yahoo.com) (The latest version 
of this document is at "http://www.milkywaygalaxy.freeservers.com" . You may
want to check there for changes). Mirror sites are at - angelfire , geocities
. These sites have lot of linux goodies and tips.

Kernel re-compile is required in order to make the kernel very lean and which
will result in FASTER operating system . It is also required to support any
new devices.
-----------------------------------------------------------------------------

2.1. Precautionary Preparations

Before you build kernel, it is a good idea to do a backup of the system. If
you had not backed up your system recently then you can do it now. You can
use commercial backup tools like BRS Backup-Recovery-Software (also in this
page you can find open-source/freeware backup tools listed under 'Backup and
Restore Utility'). Backup is just a suggestion and it is not mandatory to do
backup before building the Linux kernel.
-----------------------------------------------------------------------------

2.2. Minor Upgrading of Kernel

If you had already built the kernel and you want to upgrade to next patch
release, then you can simply copy the existing config file and reuse it. (For
example you have built kernel 2.4.19 and want to upgrade to 2.4.20).

For minor upgrades : This step may save you time, if you want to reuse the
old settings. Whenever you install the kernel, generally you put the config
file in /boot. So, you can use the existing version of config file:
        bash# mv /usr/src/linux/.config  /usr/src/linux/.config.save         
        bash# cp /boot/config-2.4.18-19.8.0  /usr/src/linux/.config          
                                                                             
Or another method is - you can copy the .config file from your old linux
kernel source tree to new kernel tree.
        bash# ls -l /usr/src/lin*  # You can see that /usr/src/linux is a soft link  
        bash# cd /usr/src/linux                                                      
        bash# cp ../linux-old-tree/.config .  # Example cp ../linux-2.4.19/.config . 
                                                                                     

or one other method is - you can use "make oldconfig" which default all
questions based on the contents of your existing ./.config file.

NOTE: If you do not have lot of disk space in /usr/src then you can unpack
the kernel source package on any partition where you have free disk space
(like /home). Because kernel compile needs lot of disk space for object files
like *.o. For this reason the /usr/src/linux MUST be a soft link pointing to
your source directory.

After this, look in the next section to do make and install.
-----------------------------------------------------------------------------

2.3. For the Impatient

 1. Unpack the sources
   
 2. Optional - Copy config file : You can copy the config file from your old
    linux kernel source tree to new kernel tree (may save time, if you want
    to reuse the old settings).
   
 3. make clean; make mrproper
   
 4. make xconfig
   
 5. make dep
   
 6. Give a unique name to your new Kernel - Edit /usr/src/linux/Makefile and
    change EXTRAVERSION
   
 7. nohup make bzImage
   
 8. 'make modules' and 'make modules_install'
   
 9. And you can go to lunch or go to bed (have nice Linux dreams in sleep)
    and when you come back the system is ready! And see the log with 'less
    nohup.out'.
   
10. make install # But NOT recommended - use cp /usr/src/linux/arch/i386/boot
    /bzImage /boot/bzImage.myker
   
11. Configure GRUB or LILO.
   
12. Reboot and check new kernel is booting
   
13. Create emergency boot disk - bzdisk or mkbootdisk
   
14. Optional - make rpm # To build rpm packages
   
15. Optional - make clean (If you want to free up disk space)
   

See details of above steps in the following sections....
-----------------------------------------------------------------------------

2.4. Building New Kernel - Explanation of Steps

Details of the steps mentioned in the previous section:

Note: Below 'bash#' denotes the bash prompt, you should type the commands
that appear after the 'bash#' prompt. Below are commands tested on Redhat
Linux Kernel 2.4.7-10, but it should work for other distributions with very
minor changes. It should also work for older kernel versions like 2.2, 2.0
and 1.3. It should also work for future or newer versions of kernel (with
little changes - let me know).

*Note: You can have many kernel images on your system. By following the
    steps below you do not overwrite or damage your existing kernel. These
    steps are very safe and your current kernel will be intact and will not
    be touched.
   

 1. Unpack the sources: Login in as 'root' throughout all these steps. Mount
    Redhat linux cdrom and install the linux kernel source rpm
            bash$ su - root                                          
            bash# cd /mnt/cdrom/RedHat/RPMS                          
            bash# rpm -i kernel-headers*.rpm                         
            bash# rpm -i kernel-source*.rpm                          
            bash# rpm -i dev86*.rpm                                  
            bash# rpm -i bin86*.rpm                                  
                                                                     
    (The bin86*.rpm and 'as86' is required only for OLDER Linux systems like
    Redhat 5.x. Get Intel assembler 'as86' command from dev86*.rpm on cdrom
    or from bin86-mandrake , bin86-kondara ). Also make sure that /usr/src/
    linux is soft link pointing to proper unpacked source.
            bash# cd /usr/src                                                                    
            bash# ls -l    # You should see that /usr/src/linux is soft link pointing to source  
            lrwxrwxrwx    1 root     root           19 Jan 26 11:01 linux -> linux-2.4.18-19.8.0 
            drwxr-xr-x   17 root     root         4096 Jan 25 21:08 linux-2.4.18-14              
            drwxr-xr-x   17 root     root         4096 Mar 26 12:50 linux-2.4.18-19.8.0          
            drwxr-xr-x    7 root     root         4096 Jan 14 16:32 redhat                       
                                                                                                 
    If it is not a soft link then do rename /usr/src/linux to /usr/src/
    linux-2.4.yy and create a soft link.
   
    NOTE: If you do not have lot of disk space in /usr/src then you can
    unpack the kernel source package on any partition where you have free
    disk space (like /home). Because kernel compile needs lot of disk space
    for object files like *.o. For this reason the /usr/src/linux MUST be a
    soft link pointing to your source directory.
   
 2. Optional - Copy config file : This step may save you time, if you want to
    reuse the old settings. Whenever you install the kernel, generally you
    put the config file in /boot. So, you can use the existing version of
    config file:
            bash# mv /usr/src/linux/.config  /usr/src/linux/.config.save 
            bash# cp /boot/config-2.4.18-19.8.0  /usr/src/linux/.config  
                                                                         
    Or another method is - you can copy the .config file from your old linux
    kernel source tree to new kernel tree
            bash# ls -l /usr/src/lin*  # You can see that /usr/src/linux is a soft link  
            bash# cd /usr/src/linux                                                      
            bash# cp ../linux-old-tree/.config .  # Example cp ../linux-2.4.19/.config . 
                                                                                         
    or one other method is - you can use "make oldconfig" which default all
    questions based on the contents of your existing ./.config file.
   
 3. Clean : Before doing mrproper below, you may want to backup the .config
    file.
            bash# cd /usr/src/linux                                                                         
            bash# cp .config .config.save                                                                   
            bash# make clean                                                                                
            bash# make mrproper  # Must do this if want to start clean slate or if you face lot of problems 
                                                                                                            
   
 4. Configure:
   
    +Start X-windows with 'startx'. If you are not able to start X-window
        then see next step below.
                bash# man startx                                      
                bash# startx                                          
                bash# cd /usr/src/linux                               
                bash# make xconfig                                    
                                                                      
       
    +If you are not able to start X-window above then try -
                        bash# export TERM=xterm                                                  
                        bash# make menuconfig                                                    
                If you find scrambled display, then use different terminal emulators like vt100, 
                vt102, vt220 or ansi. The display will be scrambled and will have garbage        
                characters in cases where you use telnet to login to remote linux. In such       
                cases you should use the terminal emulators like vt100, vt220.                   
                For example:                                                                     
                        bash# export TERM=vt220                                                  
                        bash# export TERM=ansi                                                   
                At a lower level of VT, use:                                                     
                        bash# export TERM=vt100                                                  
                        bash# make menuconfig                                                    
                If the menuconfig command fails then try -                                       
                        bash# make config                                                        
                                                                                                 
       
   
    The "make xconfig" or "make menuconfig" brings up a user friendly GUI
    interface. And "make config" brings up command-line console mode
    interface. You can load the configuration file from /usr/src/linux
    /.config (dot config file. Note the dot before config). Click on button
    "Load Configuration from File".
   
    Within 'make xconfig' you must do these (to avoid problems) -
   
    +VERY IMPORTANT !!! : Select proper CPU type - Pentium 3, AMD K6,
        Cyrix, Pentium 4, Intel 386, DEC Alpha, PowerPC otherwise kernel
        compile will fail and even if it compiles, it will not boot!!
       
    +Select SMP support - whether single CPU or multiple CPUs
       
    +Filesystems - Select Windows95 Vfat, MSDOS, NTFS as part of kernel
        and not as loadable modules. (My personal preference, but you are
        free to pick your own option).
       
    +Enable the Loadable kernel modules support! With this option you can
        load/unload the device drivers dynamically on running linux system on
        the fly. See the Modules chapter at Section 3 .
       
   
    Save and Exit "make xconfig". All the options which you selected is now
    saved into configuration file at /usr/src/linux/.config (dot config
    file).
   
 5. Dep : And now, do -
            bash# make dep                                           
                                                                     
   
 6. Give a unique name to your new Kernel: You can give a name to your
    kernel, so that it is unique and does not interfere with others.
            bash# cd /usr/src/linux                                  
            bash# vi Makefile                                        
                                                                     
    Here look for EXTRAVERSION = -19.8.0Blah_Blah_Blah and change to
    something like EXTRAVERSION = -19.8.0MyKernel.26Jan2003
   
 7. Do make: Read the following file (to gain some knowledge about kernel
    building. Tip: Use the color editor gvim for better readability.
            bash# gvim -R   /usr/src/linux/arch/i386/config.in                                  
            bash# man less                                                                      
            bash# less   /usr/src/linux/arch/i386/config.in                                     
            Type 'h' for help and to navigate press i, j, k, l, h or arrow, page up/down keys.  
                                                                                                
   
    Now, give the make command -
                    bash# cd /usr/src/linux                                     
                    bash# man nohup                                             
                    bash# nohup make bzImage &                                  
                    bash# man tail                                              
                    bash# tail -f nohup.out     (.... to monitor the progress)  
            This will put the kernel in /usr/src/linux/arch/i386/boot/bzImage   
                                                                                
   
 8. LOADABLE MODULES: Now, while the 'make' is cranking along in the previous
    step "Do make", you should bring up another new xterm shell window and
    follow these steps: This step is required ONLY if you had enabled
    Loadable module support in step "Configure Step" above. Loadable module
    are located in /lib/modules. You MUST do this step if you enabled or
    disabled any modules, otherwise you will get 'unresolved symbols' errors
    during or after kernel boot.
            # Bring up a new Xterm shell window and ...                                               
            bash# cd /usr/src/linux                                                                   
            # Redirect outputs such that you do not overwrite the nohup.out which is still running... 
            bash# nohup make modules 1> modules.out 2> modules.err  &                                 
            bash# make modules_install   # Do this, only after the above make command is successful   
                                                                                                      
    This will copy the modules to /lib/modules directory. See the Modules
    chapter at Section 3 .
   
 9. Now go to Lunch or Bed : Since both the make windows are cranking along,
    and now, you can go to lunch (chitchat, have nap) or go to bed (have nice
    Linux dreams in sleep) and when you wake up and come back the system is
    ready! You can check with command 'less nohup.out' to see the log of
    output.
            bash# cd /usr/src/linux                                  
            bash# less nohup.out                                     
            bash# less modules.err                                   
            bash# less modules.out                                   
            If no errors then do:                                    
            bash# make modules_install                               
                                                                     
   
10. bzImage: After bzImage is successful, copy the kernel image to /boot
    directory. You must copy the new kernel image to /boot directory,
    otherwise the new kernel MAY NOT boot. You must also copy the config file
    to /boot area to reflect the kernel image, for documentation purpose.
            bash# cp /usr/src/linux/arch/i386/boot/bzImage     /boot/bzImage.myker.26mar2001 
                                                                                             
            # You MUST copy the config file to reflect the corresponding kernel image,       
            # for documentation purpose.                                                     
            bash# cp /usr/src/linux/.config /boot/config-<your_kernelversion_date>           
                                                                                             
            # Example: cp /usr/src/linux/.config /boot/config-2.4.18-19.8.0-26mar2001        
                                                                                             
    NOTE : If you are planning to use the initrd in LILO or GRUB then you may
    want to build initrd and place it in /boot/initrd*.img. See the Appendix
    A at Section 12 .
   
   
11. Configure GRUB or LILO : There are two options for boot loading under
    Redhat Linux - GRUB and LILO.
   
    Configure GRUB: GRUB is recent and much better tool than LILO and it is
    my first preference to use GRUB. LILO is an older technology. GRUB
    differs from bootloaders such as LILO in that "it can lie to MS Windows
    and make MS Windows believe that it's installed on the first partition
    even if it's not!!" . So you can keep your current Linux system where it
    is and install Windows on the side. See the Section 14 file.
   
    Configure LILO: LILO is older tool and see the Section 13 to configure
    LILO. (see also "http://www.linuxdoc.org/HOWTO/
    LILO-crash-rescue-HOWTO.html" )
   
12. Reboot the machine and at lilo press tab key and type 'myker' If it boots
    then you did a good job! Otherwise at lilo select your old kernel, boot
    and re-try all over again. Your old kernel is still INTACT and SAFE at
    say /boot/vmlinuz-2.0.34-0.6
   
13. If your new kernel 'myker' boots and works properly, you can create the
    boot disk. Insert a blank floppy into floppy drive and -
            bash# cd /usr/src/linux                                  
            bash# make bzdisk                                        
            See also mkbootdisk -                                    
            bash# rpm -i mkbootdisk*.rpm                             
            bash# man mkbootdisk                                     
                                                                     
   
14. Build RPMs
   
    Optional - You can also build RPM packages of kernel, in case you want to
    install the new image on several machines.
            make rpm   # To build rpm packages                       
                                                                     
   
15. Clean: Optional - make clean (If you want to free up disk space)
   

-----------------------------------------------------------------------------
2.5. Troubleshooting

Having any problems? See the Section 16 .
-----------------------------------------------------------------------------

2.6. Post Kernel Building

See the Section 15 .
-----------------------------------------------------------------------------

3. Loadable Modules

Loadable kernel modules can save memory and ease configuration. The scope of
modules has grown to include filesystems, ethernet card drivers, tape
drivers, printer drivers, and more.

Loadable modules are pieces of kernel code which are not linked (included)
directly in the kernel. One compiles them separately, and can insert and
remove them into the running kernel at almost any time. Due to its
flexibility, this is now the preferred way to code certain kernel features.
Many popular device drivers, such as the PCMCIA drivers and the QIC-80/40
tape driver, are loadable modules.

See the Module-HOWTO at "http://www.tldp.org/HOWTO/Module-HOWTO" .

And see these man pages
        bash# rpm -i /mnt/cdrom/Redhat/RPMS/modutils*.rpm                    
        bash# man lsmod                                                      
        bash# man insmod                                                     
        bash# man rmmod                                                      
        bash# man depmod                                                     
        bash# man modprobe                                                   
                                                                             
For example to load the module /lib/modules/2.4.2-2/kernel/drivers/block/
loop.o , you would do :
        bash# man insmod                                                     
        bash# modprobe loop                                                  
        bash# insmod loop                                                    
        bash# lsmod                                                          
                                                                             
You can set the PATH which the insmod searches in /etc/modules.conf.
-----------------------------------------------------------------------------

3.1. Installing the module utilities

You can install the Module Utilities RPM with:
        bash# rpm -i /mnt/cdrom/Redhat/RPMS/modutils*.rpm                    
                                                                             

insmod inserts a module into the running kernel. Modules usually have a .o
extension; the example driver mentioned above is called drv_hello.o , so to
insert this, one would say ` insmod drv_hello.o '. To see the modules that
the kernel is currently using, use lsmod . The output looks like this: blah#
lsmod Module: #pages: Used by: drv_hello 1 ` drv_hello ' is the name of the
module, it uses one page (4k) of memory, and no other kernel modules depend
on it at the moment. To remove this module, use ` rmmod drv_hello '. Note
that rmmod wants a module name, not a filename; you get this from lsmod 's
listing. The other module utilities' purposes are documented in their manual
pages.
-----------------------------------------------------------------------------

3.2. Modules distributed with the kernel

As of version 2.0.30, most of everything is available as a loadable modules.
To use them, first make sure that you don't configure them into the regular
kernel; that is, don't say y to it during ` make config '. Compile a new
kernel and reboot with it. Then, cd to /usr/src/linux again, and do a ` make
modules '. This compiles all of the modules which you did not specify in the
kernel configuration, and places links to them in /usr/src/linux/modules .
You can use them straight from that directory or execute ` make
modules_install ', which installs them in /lib/modules/x.y.z , where x.y.z is
the kernel release.

This can be especially handy with filesystems. You may not use the minix or
msdos filesystems frequently. For example, if I encountered an msdos
(shudder) floppy, I would insmod /usr/src/linux/modules/msdos.o , and then
rmmod msdos when finished. This procedure saves about 50k of RAM in the
kernel during normal operation. A small note is in order for the minix
filesystem: you should always configure it directly into the kernel for use
in ``rescue'' disks.
-----------------------------------------------------------------------------

3.3. Howto Install Just A Single Module ?

Let us assume that you already did 'make modules' and 'make modules_install'.
And later you did 'make clean' to free up disk space. And now, you want to
change a "C" file in one of the modules and want to rebuild just that module
and copy the module file to /lib/modules. How do you do it?

You can compile just a single module file (say like foo.o) and install it.
For this simply edit the Makefile and change the SUBDIRS to add only those
directories you are interested.

For an example, if I am interested in installing only fs/autofs module, then
I do the following :
        cd /usr/src/linux                                                            
        cp Makefile Makefile.my                                                      
        vi Makefile.my                                                               
        # And comment out the line having 'SUBDIRS' and add the                      
        # directory you are interested, for example like fs/autofs as below :        
                #SUBDIRS        =kernel drivers mm fs net ipc lib abi crypto         
                SUBDIRS         =fs/autofs                                           
        # Save the file Makefile.my and give -                                       
        make -f Makefile.my modules                                                  
        # This will create module autofs.o                                           
        # Now, copy the module object file to destination /lib/modules               
        make -f Makefile.my modules_install                                          
        # And this will do 'cp autofs.o /lib/modules/2.4.18-19.8.0/kernel/fs/autofs' 
                                                                                     

Learn more about Makefile and make. See the manual for GNU make at

*"http://www.gnu.org/manual/make" .
   
*University of Utah Makefile "http://www.math.utah.edu/docs/info/
    make-stds_toc.html"
   
*University of Hawaii Makefile "http://www.eng.hawaii.edu/Tutor/Make"
   
*In Linux - man make
   
*In Linux - info make
   

Get familiar with the Makefile which makes the modules. The Makefile has
module line like
        modules: $(patsubst %, _mod_%, $(SUBDIRS))                           
                                                                             

The patsubst function has the syntax $(patsubst pattern,replacement,text). It
uses the percent symbol (%) the same way pattern rules do - as a string which
matches in both the pattern and the replacement text. It searches the text
for whitespace-separated words that match the pattern and substitutes the
replacement for them.

This makefile includes shell functions as well as standard make functions.
The syntax for a shell function is $(shell command). This returns the output
of the shell function (stripping new lines).
-----------------------------------------------------------------------------

4. Cloning of Linux Kernels

You may want to build a Linux kernel on a system and then you may want to
mass deploy to many identical hardware PCs. To make it easy to install your
newly built kernel on hundreds of other systems, you may want to package it
in RPMs (Redhat) or DEB package (Debian) or just tar.gz files.

 1. Build a kernel rpm package with rpmbuild -ba kernel*.spec
   
 2. Check that the kernel*.rpm generated has all the files in /lib/modules/
    2.x.x-y directory. Otherwise you may want to tar gzip the directory /lib/
    modules/2.x.x-y and take it to destination machines.
   
 3. Check that your kernel package has /boot/initrd-2.x.x-y.img file,
    otherwise you may want to tar gzip and take it to destination machines.
   
 4. And other files in /boot which are not in the kernel*.rpm package.
   

-----------------------------------------------------------------------------
5. Important questions and their answers

5.1. What does the kernel do, anyway?

The Unix kernel acts as a mediator for your programs and your hardware.
First, it does (or arranges for) the memory management for all of the running
programs (processes), and makes sure that they all get a fair (or unfair, if
you please) share of the processor's cycles. In addition, it provides a nice,
fairly portable interface for programs to talk to your hardware.

There is certainly more to the kernel's operation than this, but these basic
functions are the most important to know.
-----------------------------------------------------------------------------

5.2. Why would I want to upgrade my kernel?

Newer kernels generally offer the ability to talk to more types of hardware
(that is, they have more device drivers), they can have better process
management, they can run faster than the older versions, they could be more
stable than the older versions, and they fix silly bugs in the older
versions. Most people upgrade kernels because they want the device drivers
and the bug fixes.
-----------------------------------------------------------------------------

5.3. What kind of hardware do the newer kernels support?

See the Hardware-HOWTO . Alternatively, you can look at the ` config.in '
file in the linux source, or just find out when you try ` make config '. This
shows you all hardware supported by the standard kernel distribution, but not
everything that linux supports; many common device drivers (such as the
PCMCIA drivers and some tape drivers) are loadable modules maintained and
distributed separately.
-----------------------------------------------------------------------------

5.4. What version of gcc and libc do I need?

Linus recommends a version of gcc in the README file included with the linux
source. If you don't have this version, the documentation in the recommended
version of gcc should tell you if you need to upgrade your libc. This is not
a difficult procedure, but it is important to follow the instructions.
-----------------------------------------------------------------------------

5.5. What's a loadable module?

See the Modules chapter at Section 3 .
-----------------------------------------------------------------------------

5.6. How much disk space do I need?

It depends on your particular system configuration. First, the compressed
linux source is nearly 14 megabytes large at version 2.2.9. Many sites keep
this even after unpacking. Uncompressed and built with a moderate
configuration, it takes up another 67 MB.
-----------------------------------------------------------------------------

5.7. How long does it take?

With newer machines, the compilation takes dramatically less time than older
ones; an AMD K6-2/300 with a fast disk can do a 2.2.x kernel in about four
minutes. As for old Pentiums, 486s, and 386s, if you plan to compile one, be
prepared to wait, possibly hours, days..

If this troubles you, and you happen to have a faster machine around to
compile on, you can build on the fast machines (assuming you give it the
right parameters, that your ulilities are up-to-date, and so on), and then
transfer the kernel image to the slower machine.
-----------------------------------------------------------------------------

6. Patching the kernel

6.1. Applying a patch

Incremental upgrades of the kernel are distributed as patches. For example,
if you have Linux v1.1.45, and you notice that there's a ` patch46.gz ' out
there for it, it means you can upgrade to version 1.1.46 through application
of the patch. You might want to make a backup of the source tree first (`
make clean ' and then ` cd /usr/src; tar zcvf old-tree.tar.gz linux ' will
make a compressed tar archive for you.).

So, continuing with the example above, let's suppose that you have `
patch46.gz ' in /usr/src . cd to /usr/src and do a ` zcat patch46.gz | patch
-p0 ' (or ` patch -p0 < patch46 ' if the patch isn't compressed). You'll see
things whizz by (or flutter by, if your system is that slow) telling you that
it is trying to apply hunks, and whether it succeeds or not. Usually, this
action goes by too quickly for you to read, and you're not too sure whether
it worked or not, so you might want to use the -s flag to patch , which tells
patch to only report error messages (you don't get as much of the ``hey, my
computer is actually doing something for a change!'' feeling, but you may
prefer this..). To look for parts which might not have gone smoothly, cd to /
usr/src/linux and look for files with a .rej extension. Some versions of
patch (older versions which may have been compiled with on an inferior
filesystem) leave the rejects with a # extension. You can use ` find ' to
look for you; find . -name '*.rej' -print prints all files who live in the
current directory or any subdirectories with a .rej extension to the standard
output.

If everything went right, do a ` make clean ', ` config ', and ` dep ' as
described in sections 3 and 4.

There are quite a few options to the patch command. As mentioned above, patch
-s will suppress all messages except the errors. If you keep your kernel
source in some other place than /usr/src/linux , patch -p1 (in that
directory) will patch things cleanly. Other patch options are well-documented
in the manual page.
-----------------------------------------------------------------------------

6.2. If something goes wrong

(Note: this section refers mostly to quite old kernels)

The most frequent problem that used to arise was when a patch modified a file
called ` config.in ' and it didn't look quite right, because you changed the
options to suit your machine. This has been taken care of, but one still
might encounter it with an older release. To fix it, look at the
config.in.rej file, and see what remains of the original patch. The changes
will typically be marked with ` + ' and ` - ' at the beginning of the line.
Look at the lines surrounding it, and remember if they were set to ` y ' or `
n '. Now, edit config.in , and change ` y ' to ` n ' and ` n ' to ` y ' when
appropriate. Do a patch -p0 < config.in.rej and if it reports that it
succeeded (no fails), then you can continue on with a configuration and
compilation. The config.in.rej file will remain, but you can get delete it.

If you encounter further problems, you might have installed a patch out of
order. If patch says ` previously applied patch detected: Assume -R? ', you
are probably trying to apply a patch which is below your current version
number; if you answer ` y ', it will attempt to degrade your source, and will
most likely fail; thus, you will need to get a whole new source tree (which
might not have been such a bad idea in the first place).

To back out (unapply) a patch, use ` patch -R ' on the original patch.

The best thing to do when patches really turn out wrong is to start over
again with a clean, out-of-the-box source tree (for example, from one of the
linux-x.y.z.tar.gz files), and start again.
-----------------------------------------------------------------------------

6.3. Getting rid of the .orig files

After just a few patches, the .orig files will start to pile up. For example,
one 1.1.51 tree I had was once last cleaned out at 1.1.48. Removing the .orig
files saved over a half a meg. find . -name '*.orig' -exec rm -f {} ';' will
take care of it for you. Versions of patch which use # for rejects use a
tilde instead of .orig .

There are better ways to get rid of the .orig files, which depend on GNU
xargs : find . -name '*.orig' | xargs rm or the ``quite secure but a little
more verbose'' method: find . -name '*.orig' -print0 | xargs --null rm --
-----------------------------------------------------------------------------

6.4. Other patches

There are other patches (I'll call them ``nonstandard'') than the ones Linus
distributes. If you apply these, Linus' patches may not work correctly and
you'll have to either back them out, fix the source or the patch, install a
new source tree, or a combination of the above. This can become very
frustrating, so if you do not want to modify the source (with the possibility
of a very bad outcome), back out the nonstandard patches before applying
Linus', or just install a new tree. Then, you can see if the nonstandard
patches still work. If they don't, you are either stuck with an old kernel,
playing with the patch or source to get it to work, or waiting (possibly
begging) for a new version of the patch to come out.

How common are the patches not in the standard distribution? You will
probably hear of them. I used to use the noblink patch for my virtual
consoles because I hate blinking cursors (This patch is (or at least was)
frequently updated for new kernel releases.). With most newer device drivers
being developed as loadable modules, though, the frequecy of ``nonstandard''
patches is decreasing significantly.
-----------------------------------------------------------------------------

7. Tips and tricks

7.1. Redirecting output of the make or patch commands

If you would like logs of what those ` make ' or ` patch ' commands did, you
can redirect output to a file. First, find out what shell you're running: `
grep root /etc/passwd ' and look for something like ` /bin/csh '.

If you use sh or bash, (command) 2>&1 | tee (output file) will place a copy
of (command) 's output in the file ` (output file) '.

For csh or tcsh, use (command) |& tee (output file)

For rc (Note: you probably do not use rc) it's (command) >[2=1] | tee (output
file)
-----------------------------------------------------------------------------

7.2. Conditional kernel install

Other than using floppy disks, there are several methods of testing out a new
kernel without touching the old one. Unlike many other Unix flavors, LILO has
the ability to boot a kernel from anywhere on the disk (if you have a large
(500 MB or above) disk, please read over the LILO documentation on how this
may cause problems). So, if you add something similar to image = /usr/src/
linux/arch/i386/boot/bzImage label = new_kernel to the end of your LILO
configuration file, you can choose to run a newly compiled kernel without
touching your old /vmlinuz (after running lilo , of course). The easiest way
to tell LILO to boot a new kernel is to press the shift key at bootup time
(when it says LILO on the screen, and nothing else), which gives you a
prompt. At this point, you can enter ` new_kernel ' to boot the new kernel.

If you wish to keep several different kernel source trees on your system at
the same time (this can take up a lot of disk space; be careful), the most
common way is to name them /usr/src/linux-x.y.z , where x.y.z is the kernel
version. You can then ``select'' a source tree with a symbolic link; for
example, ` ln -sf linux-1.2.2 /usr/src/linux ' would make the 1.2.2 tree
current. Before creating a symbolic link like this, make certain that the
last argument to ln is not a real directory (old symbolic links are fine);
the result will not be what you expect.
-----------------------------------------------------------------------------

7.3. Kernel updates

Russell Nelson ( nelson@crynwr.com ) summarizes the changes in new kernel
releases. These are short, and you might like to look at them before an
upgrade. They are available with anonymous ftp from "ftp://ftp.emlist.com" in
pub/kchanges or through the URL "http://www.crynwr.com/kchanges"
-----------------------------------------------------------------------------

8. Linux Kernel Textbooks and Documents

Check the following books on "The Linux Kernel" at

*Kernel book "http://kernelbook.sourceforge.net" and at "http://
    sourceforge.net/projects/kernelbook"
   
*Linux Kernel books "http://www.tldp.org/guides.html"
   
*FreeTech books "http://www.tcfb.com/freetechbooks/booklinuxdev.html"
   
*Rusty's "http://www.netfilter.org/unreliable-guides"
   
*Linux Kernel links "http://www.topology.org/soft/lkernel.html"
   
*Linux Kernel Internals "http://www.moses.uklinux.net/patches/lki.html"
   
*Books links "http://linux-mm.org/kernel-links.shtml"
   

Refer also to other relevant HOWTOs at:

*Sound-HOWTO: sound cards and utilities
   
*SCSI-HOWTO: all about SCSI controllers and devices
   
*NET-2-HOWTO: networking
   
*PPP-HOWTO: PPP networking in particular
   
*PCMCIA-HOWTO: about the drivers for your notebook
   
*ELF-HOWTO: ELF: what it is, converting..
   
*Hardware-HOWTO: overview of supported hardware
   
*Module mini-HOWTO: more on kernel modules
   
*Kerneld mini-HOWTO: about kerneld
   
*BogoMips mini-HOWTO: in case you were wondering
   

-----------------------------------------------------------------------------
9. Kernel Files Information

This section gives a "very brief" and "introduction" to some of the Linux
Kernel System. If you have time you can give one reading.
-----------------------------------------------------------------------------

9.1. vmlinuz and vmlinux

The vmlinuz is the Linux kernel executable. This is located at /boot/vmlinuz.
This can be a soft link to something like /boot/vmlinuz-2.4.18-19.8.0

The vmlinux is the uncompressed built kernel, vmlinuz is the compressed one,
that has been made bootable. (Note both names vmlinux and vmlinuz look same
except for last letter z). Generally, you don't need to worry about vmlinux,
it is just an intermediate step.

The kernel usually makes a bzImage, and stores it in arch/i386/boot, and it
is up to the user to copy it to /boot and configure GRUB or LILO.
-----------------------------------------------------------------------------

9.2. Bootloader Files

        ls -l /boot/*.b                                                       
        -rw-r--r--    1 root     root         5824 Sep  5  2002 /boot/boot.b  
        -rw-r--r--    1 root     root          612 Sep  5  2002 /boot/chain.b 
        -rw-r--r--    1 root     root          640 Sep  5  2002 /boot/os2_d.b 
                                                                              
the .b files are "bootloader" files. they are part of the dance required to
get a kernel into memory to begin with. You should NOT touch them.
-----------------------------------------------------------------------------

9.3. Message File

        ls -l /boot/message*                                                     
        -rw-r--r--    1 root     root        23108 Sep  6  2002 /boot/message    
        -rw-r--r--    1 root     root        21282 Sep  6  2002 /boot/message.ja 
                                                                                 
The 'message' file contains the message your bootloader will display,
prompting you to choose an OS. So DO NOT touch it.
-----------------------------------------------------------------------------

9.4. initrd.img

See the Appendix A at Section 12 .
-----------------------------------------------------------------------------

9.5. bzImage

The bzImage is the compressed kernel image created with command 'make
bzImage' during kernel compile.
-----------------------------------------------------------------------------

9.6. module-info

This file 'module-info' is created by anaconda/utils/modlist (specific to
Redhat Linux Anaconda installer). Other Linux distributions may be having
equivalent command.

See this script and search for "module-info" updmodules .

Below is a cut from this script:
        #!/bin/bash                                                          
        # updmodules.sh                                                      
                MODLIST=$PWD/../anaconda/utils/modlist                       
        -- snip cut                                                          
        blah blah blah                                                       
        -- snip cut                                                          
            # create the module-info file                                    
            $MODLIST --modinfo-file $MODINFO --ignore-missing --modinfo \    
                        $(ls *.o | sed 's/\.o$//') > ../modinfo              
                                                                             

The program anaconda/utils/modlist is located in anaconda-runtime*.rpm on the
Redhat CDROM
        cd /mnt/cdrom/RedHat/RPMS                                            
        rpm -i anaconda-8.0-4.i386.rpm                                       
        rpm -i anaconda-runtime-8.0-4.i386.rpm                               
        ls -l /usr/lib/anaconda-runtime/modlist                              
                                                                             
Get the source code for anaconda/utils/modlist.c from anaconda*.src.rpm at 
"http://www.rpmfind.net/linux/rpm2html/search.php?query=anaconda" .

The file 'module-info' is generated during the compile. It is an information
file that is at least used during filing proper kernel OOPS reports. It is a
list of the module entry points. It may also be used by depmod in building
the tables that are used by insmod and its kith and kin. This includes
dependancy information for other modules needed to be loaded before any other
given module, etc. "Don't remove it."

Some points about module-info:

*Is provided by the kernel rpms (built by anaconda-runtime*.rpm)
   
*Is a link to module-info-{kernel-version}
   
*Contains information about all available modules (at least those included
    in the default kernel config.)
   
*Important to anaconda - in anaconda/utils/modlist command.
   
*Might be used by kudzu to determine default parameters for modules when
    it creates entries in /etc/modules.conf. If you move module-info out of
    the way, shut down, install a new network card, and re-boot then kudzu
    would complain loudly. Look at the kudzu source code.
   

-----------------------------------------------------------------------------
9.7. config

Everytime you compile and install the kernel image in /boot, you should also
copy the corresponding config file to /boot area, for documentation and
future reference. Do NOT touch or edit these files!!
        ls -l /boot/config-*                                                                         
        -rw-r--r--    1 root     root        42111 Sep  4  2002 /boot/config-2.4.18-14               
        -rw-r--r--    1 root     root        42328 Jan 26 01:29 /boot/config-2.4.18-19.8.0           
        -rw-r--r--    1 root     root        51426 Jan 25 22:21 /boot/config-2.4.18-19.8.0BOOT       
        -rw-r--r--    1 root     root        52328 Jan 28 03:22 /boot/config-2.4.18-19.8.0-26mar2003 
                                                                                                     
-----------------------------------------------------------------------------

9.8. grub

If you are using GRUB, then there will be 'grub' directory.
        ls /boot/grub                                                                   
        device.map     ffs_stage1_5  menu.lst        reiserfs_stage1_5  stage2          
        e2fs_stage1_5  grub.conf     minix_stage1_5  splash.xpm.gz      vstafs_stage1_5 
        fat_stage1_5   jfs_stage1_5  stage1          xfs_stage1_5                       
                                                                                        
See also Section 14 file.
-----------------------------------------------------------------------------

9.9. System.map

System.map is a "phone directory" list of function in a particular build of a
kernel. It is typically a symlink to the System.map of the currently running
kernel. If you use the wrong (or no) System.map, debugging crashes is harder,
but has no other effects. Without System.map, you may face minor annoyance
messages.

Do NOT touch the System.map files.
        ls -ld /boot/System.map*                                                                                   
        lrwxrwxrwx    1 root     root           30 Jan 26 19:26 /boot/System.map -> System.map-2.4.18-19.8.0custom 
        -rw-r--r--    1 root     root       501166 Sep  4  2002 /boot/System.map-2.4.18-14                         
        -rw-r--r--    1 root     root       510786 Jan 26 01:29 /boot/System.map-2.4.18-19.8.0                     
        -rw-r--r--    1 root     root       331213 Jan 25 22:21 /boot/System.map-2.4.18-19.8.0BOOT                 
        -rw-r--r--    1 root     root       503246 Jan 26 19:26 /boot/System.map-2.4.18-19.8.0custom               
                                                                                                                   

How The Kernel Symbol Table Is Created ? System.map is produced by 'nm
vmlinux' and irrelevant or uninteresting symbols are grepped out, When you
compile the kernel, this file 'System.map' is created at /usr/src/linux/
System.map. Something like below:
        nm /boot/vmlinux-2.4.18-19.8.0 > System.map                                                                   
        # Below is the line from /usr/src/linux/Makefile                                                              
        nm vmlinux | grep -v '\(compiled\)\|\(\.o$$\)\|\( [aUw] \)\|\(\.\.ng$$\)\|\(LASH[RL]DI\)' | sort > System.map 
        cp /usr/src/linux/System.map /boot/System.map-2.4.18-14   # For v2.4.18                                       
                                                                                                                      

From "http://www.dirac.org/linux/systemmap.html"
-----------------------------------------------------------------------------

9.9.1. System.map

There seems to be a dearth of information about the System.map file. It's
really nothing mysterious, and in the scheme of things, it's really not that
important. But a lack of documentation makes it shady. It's like an earlobe;
we all have one, but nobody really knows why. This is a little web page I
cooked up that explains the why.

Note, I'm not out to be 100% correct. For instance, it's possible for a
system to not have /proc filesystem support, but most systems do. I'm going
to assume you "go with the flow" and have a fairly typical system.

Some of the stuff on oopses comes from Alessandro Rubini's "Linux Device
Drivers" which is where I learned most of what I know about kernel
programming.
-----------------------------------------------------------------------------

9.9.2. What Are Symbols?

In the context of programming, a symbol is the building block of a program:
it is a variable name or a function name. It should be of no surprise that
the kernel has symbols, just like the programs you write. The difference is,
of course, that the kernel is a very complicated piece of coding and has
many, many global symbols.
-----------------------------------------------------------------------------

9.9.3. What Is The Kernel Symbol Table?

The kernel doesn't use symbol names. It's much happier knowing a variable or
function name by the variable or function's address. Rather than using size_t
BytesRead, the kernel prefers to refer to this variable as (for example)
c0343f20.

Humans, on the other hand, do not appreciate names like c0343f20. We prefer
to use something like size_t BytesRead. Normally, this doesn't present much
of a problem. The kernel is mainly written in C, so the compiler/linker
allows us to use symbol names when we code and allows the kernel to use
addresses when it runs. Everyone is happy.

There are situations, however, where we need to know the address of a symbol
(or the symbol for an address). This is done by a symbol table, and is very
similar to how gdb can give you the function name from a address (or an
address from a function name). A symbol table is a listing of all symbols
along with their address. Here is an example of a symbol table:

           c03441a0 B dmi_broken                                             
           c03441a4 B is_sony_vaio_laptop                                    
           c03441c0 b dmi_ident                                              
           c0344200 b pci_bios_present                                       
           c0344204 b pirq_table                                             
           c0344208 b pirq_router                                            
           c034420c b pirq_router_dev                                        
           c0344220 b ascii_buffer                                           
           c0344224 b ascii_buf_bytes                                        
                                                                             

You can see that the variable named dmi_broken is at the kernel address
c03441a0.
-----------------------------------------------------------------------------

9.9.4. What Is The System.map File?

There are 2 files that are used as a symbol table:

 1. /proc/ksyms
   
 2. System.map
   

There. You now know what the System.map file is.

Every time you compile a new kernel, the addresses of various symbol names
are bound to change.

/proc/ksyms is a "proc file" and is created on the fly when a kernel boots
up. Actually, it's not really a file; it's simply a representation of kernel
data which is given the illusion of being a disk file. If you don't believe
me, try finding the filesize of /proc/ksyms. Therefore, it will always be
correct for the kernel that is currently running..

However, System.map is an actual file on your filesystem. When you compile a
new kernel, your old System.map has wrong symbol information. A new
System.map is generated with each kernel compile and you need to replace the
old copy with your new copy.
-----------------------------------------------------------------------------

9.9.5. What Is An Oops?

What is the most common bug in your homebrewed programs? The segfault. Good
ol' signal 11.

What is the most common bug in the Linux kernel? The segfault. Except here,
the notion of a segfault is much more complicated and can be, as you can
imagine, much more serious. When the kernel dereferences an invalid pointer,
it's not called a segfault -- it's called an "oops". An oops indicates a
kernel bug and should always be reported and fixed.

Note that an oops is not the same thing as a segfault. Your program cannot
recover from a segfault. The kernel doesn't necessarily have to be in an
unstable state when an oops occurs. The Linux kernel is very robust; the oops
may just kill the current process and leave the rest of the kernel in a good,
solid state.

An oops is not a kernel panic. In a panic, the kernel cannot continue; the
system grinds to a halt and must be restarted. An oops may cause a panic if a
vital part of the system is destroyed. An oops in a device driver, for
example, will almost never cause a panic.

When an oops occurs, the system will print out information that is relevent
to debugging the problem, like the contents of all the CPU registers, and the
location of page descriptor tables. In particular, the contents of the EIP
(instruction pointer) is printed. Like this:
           EIP: 0010:[<00000000>]                                            
           Call Trace: [<c010b860>]                                          
                                                                             
-----------------------------------------------------------------------------

9.9.6. What Does An Oops Have To Do With System.map?

You can agree that the information given in EIP and Call Trace is not very
informative. But more importantly, it's really not informative to a kernel
developer either. Since a symbol doesn't have a fixed address, c010b860 can
point anywhere.

To help us use this cryptic oops output, Linux uses a daemon called klogd,
the kernel logging daemon. klogd intercepts kernel oopses and logs them with
syslogd, changing some of the useless information like c010b860 with
information that humans can use. In other words, klogd is a kernel message
logger which can perform name-address resolution. Once klogd tranforms the
kernel message, it uses whatever logger is in place to log system wide
messages, usually syslogd.

To perform name-address resolution, klogd uses System.map. Now you know what
an oops has to do with System.map.

Fine print: There are actually two types of address resolution are performed
by klogd.

*Static translation, which uses the System.map file.
   
*Dynamic translation which is used with loadable modules, doesn't use
   

System.map and is therefore not relevant to this discussion, but I'll
describe it briefly anyhow.

Klogd Dynamic Translation

Suppose you load a kernel module which generates an oops. An oops message is
generated, and klogd intercepts it. It is found that the oops occured at
d00cf810. Since this address belongs to a dynamically loaded module, it has
no entry in the System.map file. klogd will search for it, find nothing, and
conclude that a loadable module must have generated the oops. klogd then
queries the kernel for symbols that were exported by loadable modules. Even
if the module author didn't export his symbols, at the very least, klogd will
know what module generated the oops, which is better than knowing nothing
about the oops at all.

There's other software that uses System.map, and I'll get into that shortly.
-----------------------------------------------------------------------------

9.9.7. Where Should System.map Be Located?

System.map should be located wherever the software that uses it looks for it.
That being said, let me talk about where klogd looks for it. Upon bootup, if
klogd isn't given the location of System.map as an argument, it will look for
System.map in 3 places, in the following order:

 1. /boot/System.map
   
 2. /System.map
   
 3. /usr/src/linux/System.map
   

System.map also has versioning information, and klogd intelligently searches
for the correct map file. For instance, suppose you're running kernel 2.4.18
and the associated map file is /boot/System.map. You now compile a new kernel
2.5.1 in the tree /usr/src/linux. During the compiling process, the file /usr
/src/linux/System.map is created. When you boot your new kernel, klogd will
first look at /boot/System.map, determine it's not the correct map file for
the booting kernel, then look at /usr/src/linux/System.map, determine that it
is the correct map file for the booting kernel and start reading the symbols.

A few nota bene's:

*Somewhere during the 2.5.x series, the Linux kernel started to untar into
    linux-version, rather than just linux (show of hands -- how many people
    have been waiting for this to happen?). I don't know if klogd has been
    modified to search in /usr/src/linux-version/System.map yet. TODO: Look
    at the klogd srouce. If someone beats me to it, please email me and let
    me know if klogd has been modified to look in the new directory name for
    the linux source code.
   
*The man page doesn't tell the whole the story. Look at this:
   

           # strace -f /sbin/klogd | grep 'System.map'                       
           31208 open("/boot/System.map-2.4.18", O_RDONLY|O_LARGEFILE) = 2   
                                                                             

Apparently, not only does klogd look for the correct version of the map in
the 3 klogd search directories, but klogd also knows to look for the name
"System.map" followed by "-kernelversion", like System.map-2.4.18. This is
undocumented feature of klogd.

A few drivers will need System.map to resolve symbols (since they're linked
against the kernel headers instead of, say, glibc). They will not work
correctly without the System.map created for the particular kernel you're
currently running. This is NOT the same thing as a module not loading because
of a kernel version mismatch. That has to do with the kernel version, not the
kernel symbol table which changes between kernels of the same version!
-----------------------------------------------------------------------------

9.9.8. What else uses the System.map

Don't think that System.map is only useful for kernel oopses. Although the
kernel itself doesn't really use System.map, other programs such as klogd,
lsof,

           satan# strace lsof 2>&1 1> /dev/null | grep System                 
           readlink("/proc/22711/fd/4", "/boot/System.map-2.4.18", 4095) = 23 
                                                                              

and ps :

           satan# strace ps 2>&1 1> /dev/null | grep System                  
           open("/boot/System.map-2.4.18", O_RDONLY|O_NONBLOCK|O_NOCTTY) = 6 
                                                                             

and many other pieces of software like dosemu require a correct System.map.
-----------------------------------------------------------------------------

9.9.9. What Happens If I Don't Have A Healthy System.map?

Suppose you have multiple kernels on the same machine. You need a separate
System.map files for each kernel! If boot a kernel that doesn't have a
System.map file, you'll periodically see a message like: System.map does not
match actual kernel Not a fatal error, but can be annoying to see everytime
you do a ps ax. Some software, like dosemu, may not work correctly (although
I don't know of anything off the top of my head). Lastly, your klogd or
ksymoops output will not be reliable in case of a kernel oops.
-----------------------------------------------------------------------------

9.9.10. How Do I Remedy The Above Situation?

The solution is to keep all your System.map files in /boot and rename them
with the kernel version. Suppose you have multiple kernels like:

*/boot/vmlinuz-2.2.14
   
*/boot/vmlinuz-2.2.13
   

Then just rename your map files according to the kernel version and put them
in /boot, like:
           /boot/System.map-2.2.14                                           
           /boot/System.map-2.2.13                                           
                                                                             

Now what if you have two copies of the same kernel? Like:

*/boot/vmlinuz-2.2.14
   
*/boot/vmlinuz-2.2.14.nosound
   

The best answer would be if all software looked for the following files:
           /boot/System.map-2.2.14                                           
           /boot/System.map-2.2.14.nosound                                   
                                                                             

You can also use symlinks:
           System.map-2.2.14                                                                         
           System.map-2.2.14.sound                                                                   
           ln -s System.map-2.2.14.sound System.map     # Here System.map -> System.map-2.2.14.sound 
                                                                                                     
-----------------------------------------------------------------------------

10. Mount RPMs With FTPFS

By this time, your kernel is compiled and running ok. You will have the need
to access countless number of RPMs which you may need to install in near
future. One way is to physically mount the Linux CDROMS, but there are more
than 3 Linux cdroms and it is cumbersome to remove and change the Linux
cdroms. Hence, here comes the FTPFS.

FTP File System is a Linux kernel module, enhancing the VFS with FTP volume
mounting capabilities. That is, you can "mount" FTP shared directories in
your very personal file system and take advantage of local files ops. It is
at "http://lufs.sourceforge.net/lufs" and at "http://ftpfs.sourceforge.net" .
-----------------------------------------------------------------------------

10.1. Using the ftpfs

Download the ftpfs and install it on your system. The ftpfs is installed as a
module in /lib/modules/2.4.18-19.8.0/kernel/fs/ftpfs/ftpfs.o. And also the
command ftpmount is in /usr/bin/ftpmount. And you can do the following:

Login as root (su - root) and run this script:
        #!/bin/sh -x                                                                          
        # Use this script to mount ftp redhat cdroms rpms directory disk1,2,3                 
        # Built rpm by name ftpfs.                                                            
        # http://lufs.sourceforge.net/main/projects.html                                      
        # ftpmount --help                                                                     
        # Try this: ftpmount [user[:pass]@]host_name[:port][/root_dir] mount_point [-o]       
        # [-uid=id] [gid=id] [fmask=mask] [dmask=mask]                                        
        #ftpmount anonymous:pass@ftp.kernel.org /mnt/ftpfs                                    
        #mkdir -p /mnt/ftpfs /mnt/ftpfs/updates /mnt/ftpfs/rpms /mnt/ftpfs/contrib            
        # Redhat ftp mirror sites - http://www.redhat.com/download/mirror.html                
        FTPSITE="csociety-ftp.ecn.purdue.edu"                                                 
        USER="anonymous:pass"                                                                 
        ftpmount $USER@$FTPSITE/pub/redhat/redhat  /mnt/ftpfs/site                            
        ftpmount $USER@$FTPSITE/pub/redhat/redhat/linux/updates/8.0/en/os  /mnt/ftpfs/updates 
        ftpmount $USER@$FTPSITE/pub/redhat/redhat/linux/8.0/en/os/i386/RedHat /mnt/ftpfs/rpms 
        ftpmount $USER@$FTPSITE/pub/redhat-contrib /mnt/ftpfs/contrib                         
                                                                                              
-----------------------------------------------------------------------------

10.2. The ftpfs Commands

Before you even start thinking about mounting FTP volumes, make sure you have
a decent bandwidth or it's gonna suck.
-----------------------------------------------------------------------------

10.2.1. The autofs way - A must try!

If you were wise enough to install the autofs/automount bridge (check out the
installation notes) there is a cool way to use ftpfs: just try to access any
file/dir on the desired server under /mnt/ftpfs.
        cd /mnt/ftpfs/[user:pass@]ftp_server[:port]                          
                                                                             

Something like cd /mnt/ftpfs/ftp.kernel.org. And guess what? You're there!

Normally you will only use this for anonymous ftp since you don't want your
user/pass info to show up in the /mnt/ftpfs/ tree.
-----------------------------------------------------------------------------

10.2.2. The ftpmount way

ftpmount [user[:password]@]hostname[:port ][/root_dir] mount_point [-own]
[-uid=id] [-gid=id] [-fmask=mask] [-dmask=mask] [-active]

        The parameters: [defaults]                                                                                                                                                 
            * user: The user to be used for logging on the FTP server. [anonymous]                                                                                                 
            * password: The password for that user. [user@ftpfs.sourceforge.net]                                                                                                   
            * hostname: The FTP server.                                                                                                                                            
            * port: The port the server is listening on. [21]                                                                                                                      
            * root_dir: The directory on the FTP server you want to be mounted. This should be specified without the trailing slash (that is "/home/duru", not "/home/duru/"). [/] 
            * mount_point: The local directory you want to mount the FTP server onto.                                                                                              
            * own: Flag to force ownership on all remote files. Useful for FTP servers that list user IDs instead of user names.                                                   
            * uid: The local user ID you want to be the owner of the mounted tree.                                                                                                 
            * gid: The local group ID you want to own the mounted tree.                                                                                                            
            * fmask: The numeric mode to be ORed on all mounted files.                                                                                                             
            * dmask: The numeric mode to be ORed on all mounted dirs.                                                                                                              
            * active: Flag to enable active mode for FTP transfers. Useful if you're behind some firewall and cannot connect to random ports.                                      
                                                                                                                                                                                   

Eg: ftpmount mali@ftp.linuxnet.wox.org /mnt/ftpfs -uid=500 -gid=500 -dmask=
555

It is generally a good idea not to provide your password as a parameter,
since ftpmount will ask for it.
-----------------------------------------------------------------------------

10.2.3. The mount way

If for some reason you choose not to use ftpmount (you probably installed the
kernel patch and are too lazy to install ftpmount too), here's the way to use
good-ol mount:

mount -n -t ftpfs none mount_point -o ip=server_ip [,user=user_name] [,pass=
password] [,port=server_port] [,root= root_dir] [,own] [,uid=id] [,gid=id]
[,fmode=mask] [,dmode=mask] [,active]

Please note that you have to provide the server's IP and that the only way to
enter a password is in clear. For example, while testing, I used the
following command:

mount -n -t ftpfs none /mnt/ftpfs -o ip=127.0.0.1,user=mali,pass=my_pass
-----------------------------------------------------------------------------

10.2.4. Some notes

To unmount the volume, you go like
        umount mount_point                                                   
                                                                             

The own option (-o for ftpmount) forces ownership by the mounting user on all
files. This is useful for accommodating servers with strange user/permissions
management (SERVU & stuff).

A few words of wisdom:

*Use -n mount option! I bet you don't want your user/password information
    listed in mtab.
   
*Don't push it! (pushing it = a dozen processes reading on the mount
    point)
   
*It works best for one process! While concurrent access (under normal
    circumstances) shouldn't cause any problem, the output is optimized for
    one process reading (the TCP connection is kept alive). So, if you're
    gonna watch a movie, you don't want other processes to access the mount
    point and kill the throughoutput (trust me!).
   
*The address in IP format sucks! - Go get ftpmount.
   

-----------------------------------------------------------------------------
11. Other Formats of this Document

This section is written by Al Dev (at site "http://
www.milkywaygalaxy.freeservers.com" mirrors at angelfire , geocities , 
virtualave , Fortunecity , Freewebsites , Tripod , 101xs , 50megs )

This document is published in 14 different formats namely - DVI, Postscript,
Latex, Adobe Acrobat PDF, LyX, GNU-info, HTML, RTF(Rich Text Format),
Plain-text, Unix man pages, single HTML file, SGML (Linuxdoc format), SGML
(Docbook format), MS WinHelp format.

This howto document is located at -

*"http://www.linuxdoc.org" and click on HOWTOs and search for howto
    document name using CTRL+f or ALT+f within the web-browser.
   

You can also find this document at the following mirrors sites -

*"http://www.caldera.com/LDP/HOWTO"
   
*"http://www.linux.ucla.edu/LDP"
   
*"http://www.cc.gatech.edu/linux/LDP"
   
*"http://www.redhat.com/mirrors/LDP"
   
*Other mirror sites near you (network-address-wise) can be found at "http:
    //www.linuxdoc.org/mirrors.html" select a site and go to directory /LDP/
    HOWTO/xxxxx-HOWTO.html
   

*You can get this HOWTO document as a single file tar ball in HTML, DVI,
    Postscript or SGML formats from - "ftp://www.linuxdoc.org/pub/Linux/docs/
    HOWTO/other-formats/" and "http://www.linuxdoc.org/docs.html#howto"
   
*Plain text format is in: "ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO" 
    and "http://www.linuxdoc.org/docs.html#howto"
   
*Single HTML file format is in: "http://www.linuxdoc.org/docs.html#howto"
   
    Single HTML file can be created with command (see man sgml2html) -
    sgml2html -split 0 xxxxhowto.sgml
   
*Translations to other languages like French, German, Spanish, Chinese,
    Japanese are in "ftp://www.linuxdoc.org/pub/Linux/docs/HOWTO" and "http:/
    /www.linuxdoc.org/docs.html#howto" Any help from you to translate to
    other languages is welcome.
   

The document is written using a tool called "SGML-Tools" which can be got
from - "http://www.sgmltools.org" Compiling the source you will get the
following commands like

*sgml2html xxxxhowto.sgml (to generate html file)
   
*sgml2html -split 0 xxxxhowto.sgml (to generate a single page html file)
   
*sgml2rtf xxxxhowto.sgml (to generate RTF file)
   
*sgml2latex xxxxhowto.sgml (to generate latex file)
   

-----------------------------------------------------------------------------
11.1. Acrobat PDF format

PDF file can be generated from postscript file using either acrobat distill 
or Ghostscript . And postscript file is generated from DVI which in turn is
generated from LaTex file. You can download distill software from "http://
www.adobe.com" . Given below is a sample session:
        bash$ man sgml2latex                                                 
        bash$ sgml2latex filename.sgml                                       
        bash$ man dvips                                                      
        bash$ dvips -o filename.ps filename.dvi                              
        bash$ distill filename.ps                                            
        bash$ man ghostscript                                                
        bash$ man ps2pdf                                                     
        bash$ ps2pdf input.ps output.pdf                                     
        bash$ acroread output.pdf &                                          
                                                                             
Or you can use Ghostscript command ps2pdf . ps2pdf is a work-alike for nearly
all the functionality of Adobe's Acrobat Distiller product: it converts
PostScript files to Portable Document Format (PDF) files. ps2pdf is
implemented as a very small command script (batch file) that invokes
Ghostscript, selecting a special "output device" called pdfwrite . In order
to use ps2pdf, the pdfwrite device must be included in the makefile when
Ghostscript was compiled; see the documentation on building Ghostscript for
details.
-----------------------------------------------------------------------------

11.2. Convert Linuxdoc to Docbook format

This document is written in linuxdoc SGML format. The Docbook SGML format
supercedes the linuxdoc format and has lot more features than linuxdoc. The
linuxdoc is very simple and is easy to use. To convert linuxdoc SGML file to
Docbook SGML use the program ld2db.sh and some perl scripts. The ld2db output
is not 100% clean and you need to use the clean_ld2db.pl perl script. You may
need to manually correct few lines in the document.

*Download ld2db program from "http://www.dcs.gla.ac.uk/~rrt/docbook.html" 
    or from Milkyway Galaxy site
   
*Download the cleanup_ld2db.pl perl script from from Milkyway Galaxy site
   

The ld2db.sh is not 100% clean, you will get lot of errors when you run
                bash$ ld2db.sh file-linuxdoc.sgml db.sgml                    
                bash$ cleanup.pl db.sgml > db_clean.sgml                     
                bash$ gvim db_clean.sgml                                     
                bash$ docbook2html db.sgml                                   
                                                                             
And you may have to manually edit some of the minor errors after running the
perl script. For e.g. you may need to put closing tag < /Para> for each <
Listitem>
-----------------------------------------------------------------------------

11.3. Convert to MS WinHelp format

You can convert the SGML howto document to Microsoft Windows Help file, first
convert the sgml to html using:
                bash$ sgml2html xxxxhowto.sgml     (to generate html file)                      
                bash$ sgml2html -split 0   xxxxhowto.sgml (to generate a single page html file) 
                                                                                                
Then use the tool HtmlToHlp . You can also use sgml2rtf and then use the RTF
files for generating winhelp files.
-----------------------------------------------------------------------------

11.4. Reading various formats

In order to view the document in dvi format, use the xdvi program. The xdvi
program is located in tetex-xdvi*.rpm package in Redhat Linux which can be
located through ControlPanel | Applications | Publishing | TeX menu buttons.
To read dvi document give the command -
+---------------------------------------------------------------------------+
|          xdvi -geometry 80x90 howto.dvi man xdvi                          |
|                                                                           |
+---------------------------------------------------------------------------+
And resize the window with mouse. To navigate use Arrow keys, Page Up, Page
Down keys, also you can use 'f', 'd', 'u', 'c', 'l', 'r', 'p', 'n' letter
keys to move up, down, center, next page, previous page etc. To turn off
expert menu press 'x'.

You can read postscript file using the program 'gv' (ghostview) or
'ghostscript'. The ghostscript program is in ghostscript*.rpm package and gv
program is in gv*.rpm package in Redhat Linux which can be located through
ControlPanel | Applications | Graphics menu buttons. The gv program is much
more user friendly than ghostscript. Also ghostscript and gv are available on
other platforms like OS/2, Windows 95 and NT, you view this document even on
those platforms.

*Get ghostscript for Windows 95, OS/2, and for all OSes from "http://
    www.cs.wisc.edu/~ghost"
   

To read postscript document give the command -
+---------------------------------------------------------------------------+
|          gv howto.ps ghostscript howto.ps                                 |
|                                                                           |
+---------------------------------------------------------------------------+

You can read HTML format document using Netscape Navigator, Microsoft
Internet explorer, Redhat Baron Web browser or any of the 10 other web
browsers.

You can read the latex, LyX output using LyX a X-Windows front end to latex.
-----------------------------------------------------------------------------

12. Appendix A - Creating initrd.img file

The initrd is the "initial ramdisk". It is enough files stored in a ramdisk
to store needed drivers . You need the drivers so that the kernel can mount /
and kick off init.

You can avoid this if you build your scsi drivers right into the kernel,
instead of into modules. (Many persons recommend this).
-----------------------------------------------------------------------------

12.1. Using mkinitrd

The mkinitrd utility creates an initrd image in a single command. This is
command is peculiar to RedHat. There may be equivalent command of mkinitrd in
other distributions of Linux. This is very convenient utility.

You can read the mkinitrd man page.

        /sbin/mkinitrd --help   # Or simply type 'mkinitrd --help'                             
        usage: mkinitrd [--version] [-v] [-f] [--preload <module>]                             
               [--omit-scsi-modules] [--omit-raid-modules] [--omit-lvm-modules]                
               [--with=<module>] [--image-version] [--fstab=<fstab>] [--nocompress]            
               [--builtin=<module>] [--nopivot] <initrd-image> <kernel-version>                
               (example: mkinitrd /boot/initrd-2.2.5-15.img 2.2.5-15)                          
        # Read the online manual page with .....                                               
        man mkinitrd                                                                           
        su - root                                                                              
        # The command below creates the initrd image file                                      
        mkinitrd  ./initrd-2.4.18-19.8.0custom.img   2.4.18-19.8.0custom                       
        ls -l initrd-2.4.18-19.8.0custom.img                                                   
        -rw-r--r--    1 root     root       127314 Mar 19 21:54 initrd-2.4.18-19.8.0custom.img 
        cp  ./initrd-2.4.18-19.8.0custom.img   /boot                                           
                                                                                               

See the following sections for the manual method of creating an initrd image.
-----------------------------------------------------------------------------

12.2. Kernel Docs

To create /boot/initrd.img see the documentation at /usr/src/linux/
Documentation/initrd.txt and see also Loopback-Root-mini-HOWTO .
-----------------------------------------------------------------------------

12.3. Linuxman Book

A cut from "http://www.linuxman.com.cy/rute/node1.html" chapter 31.7.

SCSI Installation Complications and initrd

Some of the following descriptions may be difficult to understand without
knowledge of kernel modules explained in Chapter 42. You may want to come
back to it later.

Consider a system with zero IDE disks and one SCSI disk containing a LINUX
installation. There are BIOS interrupts to read the SCSI disk, just as there
were for the IDE, so LILO can happily access a kernel image somewhere inside
the SCSI partition. However, the kernel is going to be lost without a kernel
module [See Chapter 42. The kernel doesn't support every possible kind of
hardware out there all by itself. It is actually divided into a main part
(the kernel image discussed in this chapter) and hundreds of modules
(loadable parts that reside in /lib/modules/) that support the many type of
SCSI, network, sound etc., peripheral devices.] that understands the
particular SCSI driver. So although the kernel can load and execute, it won't
be able to mount its root file system without loading a SCSI module first.
But the module itself resides in the root file system in /lib/modules/. This
is a tricky situation to solve and is done in one of two ways: either (a)
using a kernel with preenabled SCSI support or (b) using what is known as an
initrd preliminary root file system image.

The first method is what I recommend. It's a straightforward (though
time-consuming) procedure to create a kernel with SCSI support for your SCSI
card built-in (and not in a separate module). Built-in SCSI and network
drivers will also autodetect cards most of the time, allowing immediate
access to the device--they will work without being given any options
[Discussed in Chapter 42.] and, most importantly, without your having to read
up on how to configure them. This setup is known as compiled-in support for a
hardware driver (as opposed to module support for the driver). The resulting
kernel image will be larger by an amount equal to the size of module. Chapter
42 discusses such kernel compiles.

The second method is faster but trickier. LINUX supports what is known as an
initrd image ( initial rAM disk image). This is a small, +1.5 megabyte file
system that is loaded by LILO and mounted by the kernel instead of the real
file system. The kernel mounts this file system as a RAM disk, executes the
file /linuxrc, and then only mounts the real file system.

31.6 Creating an initrd Image

Start by creating a small file system. Make a directory /initrd and copy the
following files into it.

        drwxr-xr-x    7 root     root         1024 Sep 14 20:12 initrd/            
        drwxr-xr-x    2 root     root         1024 Sep 14 20:12 initrd/bin/        
        -rwxr-xr-x    1 root     root       436328 Sep 14 20:12 initrd/bin/insmod  
        -rwxr-xr-x    1 root     root       424680 Sep 14 20:12 initrd/bin/sash    
        drwxr-xr-x    2 root     root         1024 Sep 14 20:12 initrd/dev/        
        crw-r--r--    1 root     root       5,   1 Sep 14 20:12 initrd/dev/console 
        crw-r--r--    1 root     root       1,   3 Sep 14 20:12 initrd/dev/null    
        brw-r--r--    1 root     root       1,   1 Sep 14 20:12 initrd/dev/ram     
        crw-r--r--    1 root     root       4,   0 Sep 14 20:12 initrd/dev/systty  
        crw-r--r--    1 root     root       4,   1 Sep 14 20:12 initrd/dev/tty1    
        crw-r--r--    1 root     root       4,   1 Sep 14 20:12 initrd/dev/tty2    
        crw-r--r--    1 root     root       4,   1 Sep 14 20:12 initrd/dev/tty3    
        crw-r--r--    1 root     root       4,   1 Sep 14 20:12 initrd/dev/tty4    
        drwxr-xr-x    2 root     root         1024 Sep 14 20:12 initrd/etc/        
        drwxr-xr-x    2 root     root         1024 Sep 14 20:12 initrd/lib/        
        -rwxr-xr-x    1 root     root           76 Sep 14 20:12 initrd/linuxrc     
        drwxr-xr-x    2 root     root         1024 Sep 14 20:12 initrd/loopfs/     
                                                                                   

On my system, the file initrd/bin/insmod is the statically linked [meaning it
does not require shared libraries.] version copied from /sbin/
insmod.static--a member of the modutils-2.3.13 package. initrd/bin/sash is a
statically linked shell from the sash-3.4 package. You can recompile insmod
from source if you don't have a statically linked version. Alternatively,
copy the needed DLLs from /lib/ to initrd/lib/. (You can get the list of
required DLLs by running ldd /sbin/insmod. Don't forget to also copy symlinks
and run strip -s {lib} to reduce the size of the DLLs.)

Now copy into the initrd/lib/ directory the SCSI modules you require. For
example, if we have an Adaptec AIC-7850 SCSI adapter, we would require the
aic7xxx.o module from /lib/modules/{version}/scsi/aic7xxx.o. Then, place it
in the initrd/lib/ directory.

        -rw-r--r--    1 root     root       129448 Sep 27  1999 initrd/lib/aic7xxx.o 
                                                                                     

The file initrd/linuxrc should contain a script to load all the modules
needed for the kernel to access the SCSI partition. In this case, just the
aic7xxx module [ insmod can take options such as the IRQ and IO-port for the
device. See Chapter 42.]:

        #!/bin/sash                                                          
                                                                             
        aliasall                                                             
                                                                             
        echo "Loading aic7xxx module"                                        
        insmod /lib/aic7xxx.o                                                
                                                                             

Now double-check all your permissions and then chroot to the file system for
testing.

        chroot ~/initrd /bin/sash                                            
        /linuxrc                                                             
                                                                             

Now, create a file system image similar to that in Section 19.9:
        dd if=/dev/zero of=~/file-inird count=2500 bs=1024                   
        losetup /dev/loop0 ~/file-inird                                      
        mke2fs /dev/loop0                                                    
        mkdir ~/mnt                                                          
        mount /dev/loop0 ~/mnt                                               
        cp -a initrd/* ~/mnt/                                                
        umount ~/mnt                                                         
        losetup -d /dev/loop0                                                
                                                                             

Finally, gzip the file system to an appropriately named file:
        gzip -c ~/file-inird > initrd-<kernel-version>                       
                                                                             

31.7 Modifying lilo.conf for initrd

Your lilo.conf file can be changed slightly to force use of an initrd file
system. Simply add the initrd option. For example:

        boot=/dev/sda                                                        
        prompt                                                               
        timeout = 50                                                         
        compact                                                              
        vga = extended                                                       
        linear                                                               
        image = /boot/vmlinuz-2.2.17                                         
                initrd = /boot/initrd-2.2.17                                 
                label = linux                                                
                root = /dev/sda1                                             
                read-only                                                    
                                                                             

Notice the use of the linear option. This is a BIOS trick that you can read
about in lilo(5). It is often necessary but can make SCSI disks nonportable
to different BIOSs (meaning that you will have to rerun lilo if you move the
disk to a different computer).
-----------------------------------------------------------------------------

13. Appendix B - Sample lilo.conf

See also Section 14 file.

Always give a date extension to the filename, because it tells you when you
built the kernel, as shown below:
        bash# man lilo                                                       
        bash# man lilo.conf                                                  
        And edit /etc/lilo.conf file and put these lines -                   
                image=/boot/bzImage.myker.26mar2001                          
                label=myker                                                  
                root=/dev/hda1                                               
                read-only                                                    
        You can check device name for 'root=' with the command -             
                bash# df   /                                                 
        Now give -                                                           
                bash# lilo                                                   
                bash# lilo -q                                                
                                                                             
You must re-run lilo even if the entry 'myker' exists, everytime you create a
new bzImage.

Given below is a sample /etc/lilo.conf file. You should follow the naming
conventions like ker2217 (for kernel 2.2.17), ker2214 (for kernel 2.2.14).
You can have many kernel images on the same /boot system. On my machine I
have something like:
        boot=/dev/hda                                                        
        map=/boot/map                                                        
        install=/boot/boot.b                                                 
        prompt                                                               
        timeout=50                                                           
        default=firewall                                                     
        image=/boot/vmlinuz-2.2.14-5.0                                       
                label=ker2214                                                
                read-only                                                    
                root=/dev/hda9                                               
        image=/boot/vmlinuz-2.2.17-14                                        
                label=ker2217                                                
                read-only                                                    
                root=/dev/hda9                                               
        #image=/usr/src/linux/arch/i386/boot/bzImage                         
        #       label=myker                                                  
        #       root=/dev/hda7                                               
        #       read-only                                                    
        image=/boot/bzImage.myker.11feb2001                                  
                label=myker11feb                                             
                root=/dev/hda9                                               
                read-only                                                    
        image=/boot/bzImage.myker.01jan2001                                  
                label=myker01jan                                             
                root=/dev/hda9                                               
                read-only                                                    
        image=/boot/bzImage.myker-firewall.16mar2001                         
                label=firewall                                               
                root=/dev/hda9                                               
                read-only                                                    
                                                                             
-----------------------------------------------------------------------------

14. Appendix C - GRUB Details And A Sample grub.conf

See

*"http://www.tldp.org/HOWTO/Linux+Win9x+Grub-HOWTO/intro.html"
   
*GNU GRUB "http://www.gnu.org/software/grub"
   
*Redhat Manual .
   
*Multiboot-with-GRUB minihowto
   
*Grub Manual
   

        bash# man grub                                                                 
        bash# man grubby   # (command line tool for configuring grub, lilo, and elilo) 
        bash# man grub-install                                                         
                                                                                       
Edit the file /etc/grub.conf to make entries for the new kernel. See the
sample file below:

        # grub.conf generated by anaconda                                                 
        #                                                                                 
        # Note that you do not have to rerun grub after making changes to this file       
        # NOTICE:  You do not have a /boot partition.  This means that                    
        #          all kernel and initrd paths are relative to /, eg.                     
        #          root (hd0,8)                                                           
        #          kernel /boot/vmlinuz-version ro root=/dev/hda9                         
        #          initrd /boot/initrd-version.img                                        
        #boot=/dev/hda                                                                    
        # By default boot the second entry                                                
        default=1                                                                         
        # Fallback to the first entry.                                                    
        fallback 0                                                                        
        # Boot automatically after 2 minutes                                              
        timeout=120                                                                       
        splashimage=(hd0,8)/boot/grub/splash.xpm.gz                                       
        title Windows 2000                                                                
        unhide (hd0,0)                                                                    
        hide (hd0,1)                                                                      
        hide (hd0,2)                                                                      
        rootnoverify (hd0,0)                                                              
        chainloader +1                                                                    
        makeactive                                                                        
        title Red Hat Linux (2.4.18-19.8.0.19mar2003)                                     
                root (hd0,8)                                                              
                kernel /boot/bzImage.2.4.18-19.8.0.19mar2003 ro root=LABEL=/ hdd=ide-scsi 
                initrd /boot/initrd-2.4.18-19.8.0custom.img.19mar03                       
        title Red Hat Linux (2.4.18-19.8.0custom)                                         
                root (hd0,8)                                                              
                kernel /boot/vmlinuz-2.4.18-19.8.0custom ro root=LABEL=/ hdd=ide-scsi     
                initrd /boot/initrd-2.4.18-19.8.0custom.img                               
        title Red Hat Linux (2.4.18-14)                                                   
                root (hd0,8)                                                              
                kernel /boot/vmlinuz-2.4.18-14 ro root=LABEL=/ hdd=ide-scsi               
                initrd /boot/initrd-2.4.18-14.img                                         
        title MyKernel.26jan03 (Red Hat Linux 2.4.18-14)                                  
                root (hd0,8)                                                              
                kernel /boot/bzImage.myker.26jan03 ro root=LABEL=/ hdd=ide-scsi           
                initrd /boot/initrd-2.4.18-19.8.0.img                                     
        title Windows 98                                                                  
        hide (hd0,0)                                                                      
        hide (hd0,1)                                                                      
        unhide (hd0,2)                                                                    
        rootnoverify (hd0,2)                                                              
        chainloader +1                                                                    
        makeactive                                                                        
        title DOS 6.22                                                                    
        hide (hd0,0)                                                                      
        unhide (hd0,1)                                                                    
        hide (hd0,2)                                                                      
        rootnoverify (hd0,1)                                                              
        chainloader +1                                                                    
        makeactive                                                                        
        title Partition 2 (floppy)                                                        
        hide (hd0,0)                                                                      
        unhide (hd0,1)                                                                    
        hide (hd0,2)                                                                      
        chainloader (fd0)+1                                                               
        title Partition 3 (floppy)                                                        
        hide (hd0,0)                                                                      
        hide (hd0,1)                                                                      
        unhide (hd0,2)                                                                    
        chainloader (fd0)+1                                                               
                                                                                          
-----------------------------------------------------------------------------

15. Appendix D - Post Kernel Building

After successfully building and booting the Linux kernel, you may be required
to do these additional steps to make some of the devices to work with Linux.
(The steps below were tested on Redhat Linux but should work with other
distributions as well.)

Video card/Monitor configuration:

*Please see the video card manual which is usually shipped with the PC.
    You should look for a "Technical Specifications" page.
   
*Please see the monitor's manual and look for a "Technical Specifications"
    page.
   

If you are using latest version of Linux (2.4 or later) and inside KDE/GNOME
desktop click on Start->"System Settings"->Display.

For older versions of Linux follow the steps below:

You can configure the Video card and monitor by using these commands:
        bash$ su - root                                                      
        bash# man Xconfigurator                                              
        bash# /usr/bin/X11/Xconfigurator --help                              
        bash# /usr/bin/X11/Xconfigurator                                     
        bash# /usr/bin/X11/Xconfigurator --expert                            
        See also:                                                            
        bash# man xf86config                                                 
        bash# /usr/bin/X11/xf86config                                        
                                                                             
If your card is not detected automatically, then you can use the --expert
option and select the "Unlisted card". If your monitor is not listed then
select the generic monitor type SVGA 1024x768.

Sound card configuration:

*Connect your external speakers to the sound card's audio port.
   
*Connect your CDROM audio wire to sound card's audio 4-pin socket.
    (Otherwise your cdrom drive will not play the music from your music cd)
   
*Refer to HOWTO docs on 'Sound' at "http://www.linuxdoc.org"
   

If you are using latest version of Linux (2.4 or later) and inside KDE/GNOME
desktop click on Start->"System Settings"->Soundcard Detection.

For older versions of Linux follow the steps below:

        bash$ su - root                                                      
        bash# man sndconfig                                                  
        bash# /usr/sbin/sndconfig                                            
                                                                             
Then start X-window 'KDE desktop' with 'startx' command. Click on 'K Start->
ControlCenter->SoundServer->General->Test Sound'. This should play the test
sound. Then click on 'K Start->MultiMedia->SoundMixer->SoundVolumeSlider' and
adjust the sound volume.

Network card configuration: If you are using latest version of Linux (2.4 or
later) and inside KDE/GNOME desktop click on Start->"System Settings"->
Network.

For older versions of Linux follow the steps below:

*Use /sbin/linuxconf
   
*Or use KDE control panel
   
*Refer to HOWTO docs on 'Networking' at "http://www.linuxdoc.org"
   

Configure Firewall and IP Masquerading : For Linux kernel version 2.4 and
above, the firewall and IP Masquerading is implemented by NetFilter package.
Hence in kernel config you should enable Netfilter and run the Firewall/
IPMasq script. Download the scripts from Firewall-IPMasq scripts , main page
of Netfilter is at "http://netfilter.samba.org" . Related materials at 
firewalling-matures and Netfilter-FAQ .

For kernel version below 2.4 you should install the firewall rpms from 
rpmfind.net or firewall.src.rpm .

Configuration of other devices: Refer to HOWTO docs relating to your devices
at "http://www.linuxdoc.org"
-----------------------------------------------------------------------------

16. Appendix E - Troubleshoot Common Mistakes

16.1. Compiles OK but does not boot

If the kernel compiles ok but booting never works and it always complains
with a kernel panic about /sbin/modprobe.

Solution: You did not create initrd image file. See the Appendix A at Section
12 . Also, you must do 'make modules' and 'make modules_install' in addition
to creating the initrd image file.
-----------------------------------------------------------------------------

16.2. The System Hangs at LILO

Sympton: After you build the kernel and reboot, the system hangs just before
LILO.

Reason: Probably you did not set the BIOS to pick up the proper Primary
Master IDE and Secondary Slave IDE hard disk partition.

Solution: Power on the machine and press DEL key to do setup of the BIOS
(Basic Input Output system). Select the IDE settings and set proper primary
hard disk partition and slave drives. When the system boots it looks for the
primary IDE hard disk and the Master Boot Record partition. It reads the MBR
and starts loading the Linux Kernel from the hard disk partition.
-----------------------------------------------------------------------------

16.3. No init found

The following mistake is commited very frequently by new users.

If your new kernel does not boot and you get -
        Warning: unable to open an initial console                           
        Kernel panic: no init found. Try passing init= option to kernel      
                                                                             
The problem is that you did not set the "root=" parameter properly in the /
etc/lilo.conf. In my case, I used root=/dev/hda1 which is having the root
partition "/". You must properly point the root device in your lilo.conf, it
can be like /dev/hdb2 or /dev/hda7.

The kernel looks for the init command which is located in /sbin/init. And /
sbin directory lives on the root partition. For details see -
        bash# man init                                                       
                                                                             
See the Section 14 file and see the Section 13 .
-----------------------------------------------------------------------------

16.4. Lot of Compile Errors

The 'make', 'make bzImage', 'make modules' or 'make modules_install' gives
compile problems. You should give 'make mrproper' before doing make.
        bash# make mrproper                                                  
                                                                             
If this problem persists, then try menuconfig instead of xconfig. Sometimes
GUI version xconfig causes some problems:
        bash# export TERM=VT100                                              
        bash# make menuconfig                                                
                                                                             
-----------------------------------------------------------------------------

16.5. The 'depmod' gives "Unresolved symbol error messages"

When you run depmod it gives "Unresolved symbols". A sample error message is
given here to demonstrate the case:
        bash$ su - root                                                                      
        bash# man depmod                                                                     
        bash# depmod                                                                         
        depmod: *** Unresolved symbols in /lib/modules/version/kernel/drivers/md/linear.o    
        depmod: *** Unresolved symbols in /lib/modules/version/kernel/drivers/md/multipath.o 
        depmod: *** Unresolved symbols in /lib/modules/version/kernel/drivers/md/raid0.o     
        depmod: *** Unresolved symbols in /lib/modules/version/kernel/drivers/md/raid1.o     
        depmod: *** Unresolved symbols in /lib/modules/version/kernel/drivers/md/raid5.o     
                                                                                             

Reason: You did not make modules and install the modules after building the
new kernel with "make bzImage" .

Solution: After you build the new kernel, you must do:
        bash$ su - root                                                      
        bash# cd /usr/src/linux                                              
        bash# make modules                                                   
        bash# make modules_install                                           
                                                                             
-----------------------------------------------------------------------------

16.6. Kernel Does Not Load Module - "Unresolved symbols" Error Messages

When you boot kernel and system tries to load any modules and you get
"Unresolved symbol : __some_function_name" then it means that you did not
clean compile the modules and kernel. It is mandatory that you should do make
clean and make the modules. Do this -
                bash# cd /usr/src/linux                                      
                bash# make dep                                               
                bash# make clean                                             
                bash# make mrproper                                          
                bash# nohup make bzImage &                                   
                bash# tail -f nohup.out     (.... to monitor the progress)   
                bash# make modules                                           
                bash# make modules_install                                   
                                                                             
-----------------------------------------------------------------------------

16.7. Kernel fails to load a module

If the kernel fails to load a module (say loadable module for network card or
other devices), then you may want to try to build the driver for device right
into the kernel. Sometimes loadable module will NOT work and the driver needs
to be built right inside the kernel. For example - some network cards do not
support loadable module feature - you MUST build the driver of the network
card right into linux kernel. Hence, in 'make xconfig' you MUST not select
loadable module for this device.
-----------------------------------------------------------------------------

16.8. Loadable modules

You can install default loadable modules with -

The step given below may not be required but is needed ONLY FOR EMERGENCIES 
where your /lib/modules files are damaged. If you already have the /lib/
modules directory and in case you want replace them use the --force to
replace the package and select appropriate cpu architecture.

For new versions of linux redhat linux 6.0 and later, the kernel modules are
included with kernel-2.2*.rpm. Install the loadable modules and the kernel
with
                This will list the already installed package.                   
        bash# rpm -qa | grep -i kernel                                          
                                                                                
        bash# rpm -U --force  /mnt/cdrom/Redhat/RPMS/kernel-2.2.14-5.0.i686.rpm 
        (or)                                                                    
        bash# rpm -U --force  /mnt/cdrom/Redhat/RPMS/kernel-2.2.14-5.0.i586.rpm 
        (or)                                                                    
        bash# rpm -U --force  /mnt/cdrom/Redhat/RPMS/kernel-2.2.14-5.0.i386.rpm 
                                                                                

This is only for old versions of redhat linux 5.2 and before. Boot new kernel
and install the loadable modules from RedHat Linux "contrib" cdrom
        bash# rpm -i /mnt/cdrom/contrib/kernel-modules*.rpm                  
        ....(For old linux systems which do not have insmod pre-installed)   
                                                                             
-----------------------------------------------------------------------------

16.9. See Docs

More problems. You can read the /usr/src/linux/README (at least once) and
also /usr/src/linux/Documentation.
-----------------------------------------------------------------------------

16.10. make clean

If your new kernel does really weird things after a routine kernel upgrade,
chances are you forgot to make clean before compiling the new kernel.
Symptoms can be anything from your system outright crashing, strange I/O
problems, to crummy performance. Make sure you do a make dep , too.
-----------------------------------------------------------------------------

16.11. Huge or slow kernels

If your kernel is sucking up a lot of memory, is too large, and/or just takes
forever to compile even when you've got your new Quadbazillium-III/4400
working on it, you've probably got lot of unneeded stuff (device drivers,
filesystems, etc) configured. If you don't use it, don't configure it,
because it does take up memory. The most obvious symptom of kernel bloat is
extreme swapping in and out of memory to disk; if your disk is making a lot
of noise and it's not one of those old Fujitsu Eagles that sound like like a
jet landing when turned off, look over your kernel configuration.

You can find out how much memory the kernel is using by taking the total
amount of memory in your machine and subtracting from it the amount of
``total mem'' in /proc/meminfo or the output of the command ` free '.
-----------------------------------------------------------------------------

16.12. The parallel port doesn't work/my printer doesn't work

Configuration options for PCs are: First, under the category `General Setup',
select `Parallel port support' and `PC-style hardware'. Then under `Character
devices', select `Parallel printer support'.

Then there are the names. Linux 2.2 names the printer devices differently
than previous releases. The upshot of this is that if you had an lp1 under
your old kernel, it's probably an lp0 under your new one. Use ` dmesg ' or
look through the logs in /var/log to find out.
-----------------------------------------------------------------------------

16.13. Kernel doesn't compile

If it does not compile, then it is likely that a patch failed, or your source
is somehow corrupt. Your version of gcc also might not be correct, or could
also be corrupt (for example, the include files might be in error). Make sure
that the symbolic links which Linus describes in the README are set up
correctly. In general, if a standard kernel does not compile, something is
seriously wrong with the system, and reinstallation of certain tools is
probably necessary.

In some cases, gcc can crash due to hardware problems. The error message will
be something like ``xxx exited with signal 15'' and it will generally look
very mysterious. I probably would not mention this, except that it happened
to me once - I had some bad cache memory, and the compiler would occasionally
barf at random. Try reinstalling gcc first if you experience problems. You
should only get suspicious if your kernel compiles fine with external cache
turned off, a reduced amount of RAM, etc.

It tends to disturb people when it's suggested that their hardware has
problems. Well, I'm not making this up. There is an FAQ for it -- it's at 
"http://www.bitwizard.nl/sig11" .
-----------------------------------------------------------------------------

16.14. New version of the kernel doesn't seem to boot

You did not run LILO, or it is not configured correctly. One thing that
``got'' me once was a problem in the config file; it said ` boot = /dev/hda1
' instead of ` boot = /dev/hda ' (This can be really annoying at first, but
once you have a working config file, you shouldn't need to change it.).
-----------------------------------------------------------------------------

16.15. You forgot to run LILO, or system doesn't boot at all

Ooops! The best thing you can do here is to boot off of a floppy disk or
CDROM and prepare another bootable floppy (such as ` make zdisk ' would do).
You need to know where your root ( / ) filesystem is and what type it is
(e.g. second extended, minix). In the example below, you also need to know
what filesystem your /usr/src/linux source tree is on, its type, and where it
is normally mounted.

In the following example, / is /dev/hda1 , and the filesystem which holds /
usr/src/linux is /dev/hda3 , normally mounted at /usr . Both are second
extended filesystems. The working kernel image in /usr/src/linux/arch/i386/
boot is called bzImage .

The idea is that if there is a functioning bzImage , it is possible to use
that for the new floppy. Another alternative, which may or may not work
better (it depends on the particular method in which you messed up your
system) is discussed after the example.

First, boot from a boot/root disk combo or rescue disk, and mount the
filesystem which contains the working kernel image:

mkdir /mnt mount -t ext2 /dev/hda3 /mnt

If mkdir tells you that the directory already exists, just ignore it. Now, cd
to the place where the working kernel image was. Note that /mnt + /usr/src/
linux/arch/i386/boot - /usr = /mnt/src/linux/arch/i386/boot Place a formatted
disk in drive ``A:'' (not your boot or root disk!), dump the image to the
disk, and configure it for your root filesystem:

cd /mnt/src/linux/arch/i386/boot dd if=bzImage of=/dev/fd0 rdev /dev/fd0 /dev
/hda1

cd to / and unmount the normal /usr filesystem:

cd / umount /mnt

You should now be able to reboot your system as normal from this floppy.
Don't forget to run lilo (or whatever it was that you did wrong) after the
reboot!

As mentioned above, there is another common alternative. If you happened to
have a working kernel image in / ( /vmlinuz for example), you can use that
for a boot disk. Supposing all of the above conditions, and that my kernel
image is /vmlinuz , just make these alterations to the example above: change
/dev/hda3 to /dev/hda1 (the / filesystem), /mnt/src/linux to /mnt , and if=
bzImage to if=vmlinuz . The note explaining how to derive /mnt/src/linux may
be ignored.

Using LILO with big drives (more than 1024 cylinders) can cause problems. See
the LILO mini-HOWTO or documentation for help on that.
-----------------------------------------------------------------------------

16.16. It says `warning: bdflush not running'

This can be a severe problem. Starting with a kernel release after Linux v1.0
(around 20 Apr 1994), a program called ` update ' which periodically flushes
out the filesystem buffers, was upgraded/replaced. Get the sources to `
bdflush ' (you should find it where you got your kernel source), and install
it (you probably want to run your system under the old kernel while doing
this). It installs itself as ` update ' and after a reboot, the new kernel
should no longer complain.
-----------------------------------------------------------------------------

16.17. I can't get my IDE/ATAPI CD-ROM drive to work

Strangely enough, lot of people cannot get their ATAPI drives working,
probably because there are a number of things that can go wrong.

If your CD-ROM drive is the only device on a particular IDE interface, it
must be jumpered as ``master'' or ``single.'' Supposedly, this is the most
common error.

Creative Labs (for one) has put IDE interfaces on their sound cards now.
However, this leads to the interesting problem that while some people only
have one interface to being with, many have two IDE interfaces built-in to
their motherboards (at IRQ15, usually), so a common practice is to make the
soundblaster interface a third IDE port (IRQ11, or so I'm told).

This causes problems with older Linux versions like 1.3 and below. in that
versions Linux don't support a third IDE interface. To get around this, you
have a few choices.

If you have a second IDE port already, chances are that you are not using it
or it doesn't already have two devices on it. Take the ATAPI drive off the
sound card and put it on the second interface. You can then disable the sound
card's interface, which saves an IRQ anyway.

If you don't have a second interface, jumper the sound card's interface (not
the sound card's sound part) as IRQ15, the second interface. It should work.
-----------------------------------------------------------------------------

16.18. It says weird things about obsolete routing requests

Get new versions of the route program and any other programs which do route
manipulation. /usr/include/linux/route.h (which is actually a file in /usr/
src/linux ) has changed.
-----------------------------------------------------------------------------

16.19. ``Not a compressed kernel Image file''

Don't use the vmlinux file created in /usr/src/linux as your boot image; [..]
/arch/i386/boot/bzImage is the right one.
-----------------------------------------------------------------------------

16.20. Problems with console terminal after upgrade to Linux v1.3.x

Change the word dumb to linux in the console termcap entry in /etc/termcap .
You may also have to make a terminfo entry.
-----------------------------------------------------------------------------

16.21. Can't seem to compile things after kernel upgrade

The linux kernel source includes a number of include files (the things that
end with .h ) which are referenced by the standard ones in /usr/include .
They are typically referenced like this (where xyzzy.h would be something in
/usr/include/linux ): #include <linux/xyzzy.h> Normally, there is a link
called linux in /usr/include to the include/linux directory of your kernel
source ( /usr/src/linux/include/linux in the typical system). If this link is
not there, or points to the wrong place, most things will not compile at all.
If you decided that the kernel source was taking too much room on the disk
and deleted it, this will obviously be a problem. Another way it might go
wrong is with file permissions; if your root has a umask which doesn't allow
other users to see its files by default, and you extracted the kernel source
without the p (preserve filemodes) option, those users also won't be able to
use the C compiler. Although you could use the chmod command to fix this, it
is probably easier to re-extract the include files. You can do this the same
way you did the whole source at the beginning, only with an additional
argument:

blah# tar zxvpf linux.x.y.z.tar.gz linux/include Note: `` make config '' will
recreate the /usr/src/linux link if it isn't there.
-----------------------------------------------------------------------------

16.22. Increasing limits

The following few example commands may be helpful to those wondering how to
increase certain soft limits imposed by the kernel: echo 4096 > /proc/sys/
kernel/file-max echo 12288 > /proc/sys/kernel/inode-max echo 300 400 500 > /
proc/sys/vm/freepages
