2.1. Precautionary Preparations

Перед компиляцией ядра нужно сделать бэкап системы , хотя вообще-то это дело вкуса . Можно использовать для этого коммерческую тулзу BRS Backup-Recovery-Software

При компиляции старый конфиг нужно сохранить. Например , вот так :

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

Другой способ - скопировать конфиг из предыдущего каталога исходников ядра в новый каталог :

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 .

или вот так - "make oldconfig"

2.3. For the Impatient

1. Распаковываем исходники из архива

2. Сохраняем старый конфиг

3. make clean; make mrproper

4. make xconfig

5. make dep

6. Даем уникальное имя для нового ядра - подправляем /usr/src/linux/Makefile или меняем EXTRAVERSION

7. nohup make bzImage

8. 'make modules' и 'make modules_install'

9. И можно идти на обед. Прийдя с обеда , можно посмотреть 'less nohup.out'.

10. make install [num ] Физически при этом происходит следующее - use cp /usr/src/linux/arch/i386/boot/bzImage /boot/bzImage.myker

11. Конфигурируем GRUB или LILO.

12. Перезапуск

13. Создаем загрузочный диск - bzdisk или mkbootdisk

14. Создаем пакет - make rpm [num ]

15. Подчистим - make clean

2.4. Building New Kernel - Explanation of Steps

Все нижеследующее проверялось на Redhat Linux Kernel 2.4.7-10, но с небольшими изминениями должно работать на предыдущих и будущих версиях.

1. Распаковка исходников с сидирома :

   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

   assembler 'as86' извлекается из dev86*.rpm на сиди или с bin86-mandrake , bin86-kondara ). Каталог /usr/src/linux должен быть линком .

   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

   Если это не линк , то нужно переименовать каталог /usr/src/linux в каталог /usr/src/linux-2.4.yy и создать на него линк.

   Вообще-то компиляцию новой версии ядра можно делать где угодно.

2. Сохраняем старый конфиг:

   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

   Или копируем конфиг :

   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 .

   или делаем "make oldconfig"

3. Clean :

   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. Конфигурация:

   • Стартуем X-windows

     bash# man startx bash# startx bash# cd /usr/src/linux bash# make xconfig

   • Если не удалось запустить виндовую конфигурацию ядра - пробуем терминальную

     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

   Утилиты "make xconfig" или"make menuconfig" запускают интерактивный дружественный интерфейс . Команда "make config" запускает более детерминированный command-line консольный интерфейс.

   • ОЧЕНЬ ВАЖНО !!! : Выбираем соответствующий тип CPU - Pentium 3, AMD K6, Cyrix, Pentium 4, Intel 386, DEC Alpha, PowerPC - в противном случае будут либо ошибки при компиляции , либо новое ядро вообще не будет загружаться !!

   • Выбираем SMP support - один CPU или несколько

   • Выбираем Filesystems

   • Выбираем поддержку Loadable kernel modules !

   Сохраняем и выходим из "make xconfig". Изменения сохранены в /usr/src/linux/.config

5. Dep :

   bash# make dep

6. Теперь дадим уникальное имя новому ядру - пропишем это в Makefile:

   bash# cd /usr/src/linux bash# vi Makefile

   Пусть системная переменная EXTRAVERSION = -19.8.0_Blah_Blah_Blah . Меяем ее на что-то типа EXTRAVERSION = -19.8.0MyKernel.26Jan2003

7. make: Сначала читаем :

   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.

   Теперь запускаем make -

   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. Загружаемые модули: они находятся в /lib/modules.

   # 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

   Копирует модули в /lib/modules .

9. Идем обедать . Возвращаемся с обеда и смотрим лог .

   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: Копируем образ в каталог /boot , а также конфиг .

    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

11. Конфигурация GRUB или LILO : Под Redhat Linux есть 2 загрузчика - GRUB и LILO. GRUB: GRUB поновее и покруче , чем LILO . Загрузчик позволяет иметь на одном компе несколько разных осей.

12. Делаем перезапуск и в лило жмем на клавишу таб , после чего набираем 'myker' Если все грузится , значит новое ядро удалось , в противном случае будет загружен старый образ.

13. Создаем загрузочный флоппи :

    bash# cd /usr/src/linux bash# make bzdisk See also mkbootdisk - bash# rpm -i mkbootdisk*.rpm bash# man mkbootdisk

14. Закатаем новый образ в RPM

    make rpm # To build rpm packages

15. Clean: опционально .

2.5. Troubleshooting

Проблемы? Смотри Section 17 .

2.6. Post Kernel Building

Смотри Section 16 .

3.1. Installing the module utilities

Можно инсталлировать модульные утилиты так :

bash# rpm -i /mnt/cdrom/Redhat/RPMS/modutils*.rpm

insmod добавляет модуль к ядру , которое уже запущено. Модули обычно имеют расширение .o . Для того , чтобы посмотреть , какие модули использует текущее ядро надо набрать lsmod . Вывод будет примерно такой : blah# lsmod Module: #pages: Used by: drv_hello 1 ` . Для удаления модулей используйте ` rmmod drv_hello '. Обратите внимание , что rmmod требует имя модуля, а не имя файла; имя модуля можно получить с помощью lsmod '.

3.2. Modules distributed with the kernel

Начиная с версии 2.0.30, большинство модулей загружаемые . Порядок компиляции следующий : откомпилировав ядро , презапуститесь через него . Затем : cd to /usr/src/linux и выполняем ` make modules '. Эта команда откомпилирует все модули , не определенные в конфигурации и разместит линки на них в /usr/src/linux/modules . Затем выполняем ` make modules_install ', которая установит их в /lib/modules/x.y.z , где x.y.z есть номер релиза.

3.3. Howto Install Just A Single Module ?

Предположим , что вы захотели изменить код в одном из модулей и хотите перекомпилировать только его.

Можно откомпилировать единственный модуль и инсталлировать его. Для этого в Makefile можно использовать SUBDIRS для добавления только тех директорий, которые вас интересуют.

Например для модуля fs/autofs :

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'

О Makefile и make можно почитать здесь :

• "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

5.1. What does the kernel do, anyway?

Ядро управляет памятью всех процессов и обеспечивает портабельный интерфейс для общения программ с железом.

5.2. Why would I want to upgrade my kernel?

Новые версии ядра могут общаться с большим количеством железа,лучше управляют памятью, они просто быстрее старых.

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

Смотрите Hardware-HOWTO . Можно посмотреть в ` config.in ' или просто набрать ` make config '. Будет показан полный список оборудования , поддерживаемого ядром.

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

Версию gcc можно посмотреть в README .

5.5. What's a loadable module?

Смотрите Section 3 .

5.6. How much disk space do I need?

Это зависит от конфигурации . Исходники 2.2.9 весят 14 метров.

5.7. How long does it take?

На AMD K6-2/300 компиляция 2.2.x занимает около 4 минут . На 486s, и 386s, это может занимать часы ...

Можно компилировать на быстрых машинах и потом переносить на медленные.

6.1. Applying a patch

Незначительные изменения ядра называются патчами. Например , если у вас Linux v1.1.45, и у вас есть patch46.gz ' , это значит что вы можете проапгрэйдить версию до 1.1.46 с помощью этого патча. Вначале можно сделать бэкап исходников : ` make clean ' и затем ` cd /usr/src; tar zcvf old-tree.tar.gz linux ' будет создан архив.

Итак , предположим , что у нас имеется ` patch46.gz ' в каталоге /usr/src . Делаем cd /usr/src и затем ` zcat patch46.gz [verbar] patch -p0 ' (or ` patch -p0 [lt ] patch46 ' . После чего набираем -s вместе с командой patch , которая говорит patch вывести только ошибки . Затем идем в каталог /usr/src/linux и смотрим на файл .rej

Если все нормально , делаем ` make clean ', ` config ', и ` dep ' .

patch -s ничего не выводит , кроме ошибок .

6.2. If something goes wrong

Проблемы при патчах возникают после того , как изменяется config.in ' . Но есть файл config.in.rej , с помощью которого можно посмотреть разницу. Изменения маркируются ` + ' и ` - ' в начале линии. Изменив в config.in y ' на ` n ' и ` n ' на ` y ' , можно добиться желаемого результата.

6.3. Getting rid of the .orig files

В результате патчей создаются файлы .orig . Команда find . -name '*.orig' -exec rm -f {} ';' удаляет их .

6.4. Other patches

Патчи от нестандартных дистрибутивов могут привести к проблемам .

10.1. vmlinuz and vmlinux

vmlinuz - исполняемый файл ядра . Находится в /boot/vmlinuz. Часто это может быть линком на что-то типа /boot/vmlinuz-2.4.18-19.8.0

vmlinux - это несжатое ядро, vmlinuz - сжатое , создаваемое при запуске .

Еще есть bzImage, который хранится в arch/i386/boot.

10.2. Bootloader Files

Файлы с раширением .b - "bootloader" файлы. Необходимы для загрузки ядра в память.

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

10.3. Message File

Файлы 'message' включают сообщения , которые выводятся на экран.

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

10.4. initrd.img

Смотри Section 13 .

10.5. bzImage

bzImage - сжатый образ ядра , созданный командой 'make bzImage' .

10.6. 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. Refer to your Linux distributor's manual pages.

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" Read online at modlist.c . .

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-[lcub ]kernel-version[rcub ]

• 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.

10.7. 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

10.8. 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 15 file.

10.9. 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"

13.1. 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.

13.2. Kernel Docs

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

13.3. 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 [lsqb ]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 [lsqb ]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 [nbsp ]/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 [lsqb ]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 [lcub ]lib[rcub ] 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/[lcub ]version[rcub ]/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 [lsqb ] 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).

14.1. Resources on LILO

See also following documents:

• http://www.tldp.org/HOWTO/mini/LILO.html

• See the documentation of Lilo on your Linux system :

  # Use the kghostview, ghostview or gv command kghostview /usr/share/doc/lilo-21.4.4/doc/user.ps # To read in HTML format do this - mkdir $HOME/lilodocs cd $HOME/lilodocs cp /usr/share/doc/lilo-21.4.4/doc/user.tex . latex2html user # This creates the html files in user directory

• Section 15 GRUB Conf file.

• "http://www.linuxdoc.org/HOWTO/LILO-crash-rescue-HOWTO.html" .

14.2. Troubleshooting LILO

The beeper error codes :

14.3. Sample on LILO

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

15.1. References on GRUB

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
       

15.2. Tips On GRUB

In Redhat Linux, during grub display, just type c for command-line option of GRUB:

To boot Linux do this: grub> help grub> root (hd1,1): Filesystem is type ext2fs, partition type 0x83 grub> root (hd1,0) grub> kernel / <Press-TAB-KEY> This will list all files grub> kernel /boot <Press-TAB-KEY> This will list all files in /boot grub> kernel /boot/vmlinuz grub> boot

See also the GRUB Manual . To boot MS Windows 95/2000 etc do this: If you want to boot an unsupported operating system (e.g. Windows 95), chain-load a boot loader for the operating system. Normally, the boot loader is embedded in the boot sector of the partition on which the operating system is installed.

grub> help grub> help rootnoverify grub> rootnoverify (hd0,0) grub> makeactive grub> chainloader +1 grub> boot

15.3. Sample GRUB Conf File

# 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

17.1. 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 13 . Also, you must do 'make modules' and 'make modules_install' in addition to creating the initrd image file.

17.2. 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.

17.3. 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 15 file and see the Section 14 .

17.4. 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

17.5. 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

17.6. 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

17.7. 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.

17.8. 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)

17.9. See Docs

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

17.10. 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.

17.11. 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 '.

17.12. 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.

17.13. 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" .

17.14. 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.).

17.15. 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.

17.16. 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.

17.17. 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.

17.18. 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.

17.19. ``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.

17.20. 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.

17.21. 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.

17.22. 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