This section is written by Al Dev (alavoor[AT]yahoo.com)
The latest version of this section is at http://www.aldev.8m.com and click on "Quick Steps to recompile linux kernel". Mirror sites are at - angelfire, geocities, virtualave, Fortunecity, Freewebsites, Tripod, 101xs, Freeservers, 50megs, Terrashare, Escalix, Httpcity.
These sites have lots of linux goodies and tips.
(The latest version of this document is at http://www.aldev.8m.com. You may want to check there for changes).
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.
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 do it now. See Backup-Recovery-HOWTO.
Or if you feel that you can take risk of losing data, then skip this section and go to next 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, but it should work for other distributions with very minor changes.
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
bash# man startx bash# startx bash# cd /usr/src/linux bash# make xconfig
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, use: bash# export TERM=vt100 bash# make menuconfig If the menuconfig command fails then try - bash# make config
bash# rpm -i /mnt/cdrom/Redhat/RPMS/modutils*.rpm bash# man lsmod bash# man insmod bash# man rmmod bash# man depmod bash# man modprobe
bash# make dep bash# make clean
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.
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
bash# cp /usr/src/linux/arch/i386/boot/bzImage /boot/bzImage.myker.26mar2001 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 /
bash# lilo bash# lilo -q
bash# cd /usr/src/linux bash# make bzdisk See also mkbootdisk - bash# rpm -i mkbootdisk*.rpm bash# man mkbootdisk
bash# cd /usr/src/linux bash# make modules bash# make modules_install
/lib/modules/2.4.2-2/kernel/drivers/block/loop.o, you would do :
bash# man insmod bash# modproble loop bash# insmod loop bash# lsmod
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.
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 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
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
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
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# nohup make bzImage & bash# tail -f nohup.out (.... to monitor the progress) bash# make modules bash# make modules_install
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.
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)
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:
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
Sound card configuration:
bash$ su - root bash# man sndconfig bash# /usr/sbin/sndconfig
Network card configuration:
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.
Configuration of other devices: Refer to HOWTO docs relating to your devices at http://www.linuxdoc.org
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