The Linux Kernel HOWTO Brian Ward bri@cs.uchicago.edu , Al Dev (Alavoor Vasude­ van) alavoor[AT]yahoo.com v3.7, 30 March 2002 This is a detailed guide to kernel configuration, compilation, upgrades, and troubleshooting for ix86-based systems. ______________________________________________________________________ Table of Contents 1. Introduction 1.1 Read this first! (I mean it) 1.2 A word on style 2. Quick Steps - Kernel Compile 2.1 Precautionary Preparations 2.2 Building Kernel 2.3 Troublshoot Common Mistakes 2.3.1 The System Hangs at LILO 2.3.2 No init found 2.3.3 The 'depmod' gives "Unresolved symbol error messages" 2.3.4 Kernel Does Not Load Module - "Unresolved symbols" Error Messages 2.3.5 Kernel fails to load a module 2.3.6 Loadable modules 2.4 Post Kernel Building 2.5 Sample lilo.conf 3. Important questions and their answers 3.1 What does the kernel do, anyway? 3.2 Why would I want to upgrade my kernel? 3.3 What kind of hardware do the newer kernels support? 3.4 What version of gcc and libc do I need? 3.5 What's a loadable module? 3.6 How much disk space do I need? 3.7 How long does it take? 4. How to actually configure the kernel 4.1 Getting the source 4.2 Unpacking the source 4.3 Configuring the kernel 4.3.1 Kernel math emulation (Processor type and features) 4.3.2 Enhanced (MFM/RLL) disk and IDE disk/cdrom support (Block Devices) 4.3.3 Networking support (General Setup) 4.3.4 System V IPC (General Setup) 4.3.5 Processor family (Processor type and features) 4.3.6 SCSI support 4.3.7 Network device support 4.3.8 Filesystems 4.3.8.1 But I don't know which filesystems I need! 4.3.9 Character devices 4.3.10 Sound 4.3.11 Other configuration options 4.3.12 Kernel hacking 4.4 Now what? (The Makefile) 5. Compiling the kernel 5.1 Cleaning and depending 5.2 Compile time 5.3 Other ``make''ables 5.4 Installing the kernel 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. Additional packages 7.1 kbd 7.2 util-linux 7.3 hdparm 7.4 gpm 8. Some pitfalls 8.1 make clean 8.2 Huge or slow kernels 8.3 The parallel port doesn't work/my printer doesn't work 8.4 Kernel doesn't compile 8.5 New version of the kernel doesn't seem to boot 8.6 You forgot to run LILO, or system doesn't boot at all 8.7 It says `warning: bdflush not running' 8.8 I can't get my IDE/ATAPI CD-ROM drive to work 8.9 It says weird things about obsolete routing requests 8.10 Firewalling not working in 1.2.0 8.11 ``Not a compressed kernel Image file'' 8.12 Problems with console terminal after upgrade to 1.3.x 8.13 Can't seem to compile things after kernel upgrade 8.14 Increasing limits 9. Note for upgrade to version 2.0.x, 2.2.x 10. Modules 10.1 Installing the module utilities 10.2 Modules distributed with the kernel 11. Tips and tricks 11.1 Redirecting output of the make or patch commands 11.2 Conditional kernel install 11.3 Kernel updates 12. Other relevant HOWTOs that might be useful 13. Misc 13.1 Author 13.2 To do 13.3 Contributions 13.4 Copyright notice, License, and all that stuff 14. Other Formats of this Document 14.1 Acrobat PDF format 14.2 Convert Linuxdoc to Docbook format 14.3 Convert to MS WinHelp format 14.4 Reading various formats ______________________________________________________________________ 1. Introduction Should you read this document? Well, see if you've got any of the following symptoms: · ``Arg! This wizzo-46.5.6 package says it needs kernel release 2.8.193 and I still only have release 1.0.9!'' · There's a device driver in one of the newer kernels that you just gotta have · You really have no idea at all how to compile a kernel · ``Is this stuff in the README really the whole story?'' · You came, you tried, it didn't work · You need something to give to people who insist on asking you to install their kernels for them 1.1. Read this first! (I mean it) Some of the examples in this document assume that you have GNU tar, find, and xargs. These are quite standard; this should not cause problems. It is also assumed that you know your system's filesystem structure; if you don't, it is critical that you keep a written copy of the mount command's output during normal system operation (or a listing of /etc/fstab, if you can read it). This information is important, and does not change unless you repartition your disk, add a new one, reinstall your system, or something similar. The latest ``production'' kernel version at the time of this writing was 2.2.9, meaning that the references and examples correspond to that release. Even though I try to make this document as version- independent as possible, the kernel is constantly under development, so if you get a newer release, it will inevitably have some differences. Again, this should not cause major problems, but it may create some confusion. There are two versions of the linux kernel source, ``production'' and ``development.'' Production releases are the even-minor-numbered releases; 1.2.x was production, 2.0.x is production, as well as 2.2.x. These kernels are considered to be the most stable, bug-free versions available at the time of release. The development kernels (2.1.x, 2.3.x, etc) are meant as testing kernels, for people willing to test out new and possibly very buggy kernels. You have been warned. 1.2. A word on style Text that looks like this is either something that appears on your screen, a filename, or something that can be directly typed in, such as a command, or options to a command (if you're looking at a plain- text file, it doesn't look any different). Commands and other input are frequently quoted (with ` '), which causes the following classic punctuation problem: if such an item appears at the end of a sentence in quotes, people often type a `.' along with the command, because the American quoting style says to put the period inside of the quotation marks. Even though common sense (and unfortunately, this assumes that the one with the ``common sense'' is used to the so-called American style of quotation) should tell one to strip off the punctuation first, many people simply do not remember, so I will place it outside the quotation marks in such cases. In other words, when indicating that you should type ``make config'' I would write `make config', not `make config.' 2. Quick Steps - Kernel Compile This section is written by Al Dev (alavoor[AT]yahoo.com) The latest version of this section is at and click on "Quick Steps to recompile linux kernel". Mirror sites are at - angelfire , geocities , virtualave , Fortunecity , Freewebsites , Tripod , 101xs , 50megs , These sites have lots of linux goodies and tips. (The latest version of this document is at . 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. 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 do it now. See BRS Backup-Recovery-Software go here and click on BRS. Or if you feel that you can take risk of losing data, then skip this section and go to next section. 2.2. Building Kernel 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. 1. 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. 2. 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 ). 3. · 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, 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). 4. Within 'make xconfig' you must do these to avoid problems - · Select proper CPU type - Pentium 3, AMD K6, Cyrix, Pentium 4, Intel 386, DEC Alpha, PowerPC otherwise kernel 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 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 ___________________________________________________________________ 5. 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). And now, do - ___________________________________________________________________ bash# make dep bash# make clean ___________________________________________________________________ 6. 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. ___________________________________________________________________ 7. 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. 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. And then read the manual page on lilo (see also ) and see the ``sample lilo.conf'' file. Always give a date extension to the filename, because it tells you when you built the kernel, as shown below: ___________________________________________________________________ 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 / ___________________________________________________________________ 9. Now give ___________________________________________________________________ bash# lilo bash# lilo -q ___________________________________________________________________ You must re-run lilo even if the entry 'myker' exists, everytime you create a new bzImage. 10. 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 11. 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 ___________________________________________________________________ 12. LOADABLE MODULES: This step is required ONLY if you had enabled Loadable module support in step 3 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. Check for insmod command which is extensively used for loading the modules. ___________________________________________________________________ bash# cd /usr/src/linux bash# make modules bash# make modules_install ___________________________________________________________________ This will copy the modules to /lib/modules directory. For example to load the module /lib/modules/2.4.2-2/ker­ nel/drivers/block/loop.o, you would do : ______________________________________________________________________ bash# man insmod bash# modprobe loop bash# insmod loop bash# lsmod ______________________________________________________________________ You can set PATH the insmod searches in /etc/modules.conf 2.3. Troublshoot Common Mistakes 2.3.1. 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. 2.3.2. 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 ______________________________________________________________________ 2.3.3. 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 ______________________________________________________________________ 2.3.4. Kernel Does Not Load Module - "Unresolved symbols" Error Mes­ sages 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 ______________________________________________________________________ 2.3.5. 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. 2.3.6. 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) ______________________________________________________________________ 2.4. 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. 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 ___________________________________________________________________ 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->Sound­ Mixer->SoundVolumeSlider' and adjust the sound volume. Network card configuration: · Use /sbin/linuxconf · Or use KDE control panel · Refer to HOWTO docs on 'Networking' at 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 . 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 2.5. Sample lilo.conf 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 ______________________________________________________________________ 3. Important questions and their answers 3.1. 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. 3.2. 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. 3.3. 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. 3.4. 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. 3.5. What's a loadable module? These 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. 3.6. 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. 3.7. 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. 4. How to actually configure the kernel 4.1. Getting the source You can obtain the source via anonymous ftp from ftp.kernel.org in /pub/linux/kernel/vx.y, where x.y is the version (eg 2.2), and as mentioned before, the ones that end with an odd number are development releases and may be unstable. It is typically labelled linux- x.y.z.tar.gz, where x.y.z is the version number. The sites also typically carry ones with a suffix of .bz2, which have been compressed with bzip2 (these files will be smaller and take less time to transfer). It's best to use ftp.xx.kernel.org where xx is your country code; examples being ftp.at.kernel.org for Austria, and ftp.us.kernel.org for the United States. 4.2. Unpacking the source Log in as or su to `root', and cd to /usr/src. If you installed kernel source when you first installed linux (as most do), there will already be a directory called `linux' there, which contains the entire old source tree. If you have the disk space and you want to play it safe, preserve that directory. A good idea is to figure out what version your system runs now and rename the directory accordingly. The command `uname -r' prints the current kernel version. Therefore, if `uname -r' said `1.0.9', you would rename (with `mv') `linux' to `linux-1.0.9'. If you feel mildly reckless, just wipe out the entire directory. In any case, make certain there is no `linux' directory in /usr/src before unpacking the full source code. Now, in /usr/src, unpack the source with `tar zxpvf linux- x.y.z.tar.gz' (if you've just got a .tar file with no .gz at the end, `tar xpvf linux-x.y.z.tar' works.). The contents of the source will fly by. When finished, there will be a new `linux' directory in /usr/src. cd to linux and look over the README file. There will be a section with the label `INSTALLING the kernel'. Carry out the instructions when appropriate -- symbolic links that should be in place, removal of stale .o files, etc. If you have a .bz2 file and the bzip2 program (read about it at http://www.muraroa.demon.co.uk/), do this: bz2cat linux-x.y.z.tar.bz2 | tar xvf - 4.3. Configuring the kernel Note: Some of this is reiteration/clarification of a similar section in Linus' README file. The command `make config' while in /usr/src/linux starts a configure script which asks you many questions. It requires bash, so verify that bash is /bin/bash, /bin/sh, or $BASH. However, there are some much more pleasant alternatives to `make config' and you may very well find them easier and more comfortable to use. `make menuconfig' is probably the most widely-used. Whatever you choose, it's best to get familiar with the interface because you may find yourself back at it sooner than you think. For those ``running X,'' you can try `make xconfig' if you have Tk installed (`click-o- rama' - Nat). `make menuconfig' is for those who have (n)curses and would prefer a text-based menu. These interfaces have a rather clear advantage: If you goof up and make a wrong choice during configuration, it is simple to go back and fix it. The configuration options will appear in hierarchies with `make menuconfig' and `make xconfig'. You are ready to answer the questions, usually with `y' (yes) or `n' (no). Device drivers typically have an `m' option. This means ``module,'' meaning that the system will compile it, but not directly into the kernel, but as a loadable module. A more comical way to describe it is as ``maybe.'' Some of the more obvious and non-critical options are not described here; see the section ``Other configuration options'' for short descriptions of a few others. With `make menuconfig', the space bar toggles the selection. In 2.0.x and later, there is a `?' option, which provides a brief description of the configuration parameter. That information is likely to be the most up-to-date. Here are a listing of some of the important features, which hierarchy they are in, and brief description. 4.3.1. Kernel math emulation (Processor type and features) If you don't have a math coprocessor (you have a bare 386 or 486SX), you must say `y' to this. If you do have a coprocessor and you still say `y', don't worry too much -- the coprocessor is still used and the emulation ignored. For any halfway modern machine, the answer will be no, but don't worry if you say yes accidentally; if not needed, it is not used. 4.3.2. Enhanced (MFM/RLL) disk and IDE disk/cdrom support (Block Devices) You probably need to support this; it means that the kernel will support standard PC hard disks, which most people have. This driver does not include SCSI drives; they come later in the configuration. You will then be asked about the ``old disk-only'' and ``new IDE'' drivers. You want to choose one of them; the main difference is that the old driver only supports two disks on a single interface, and the new one supports a secondary interface and IDE/ATAPI cdrom drives. The new driver is 4k larger than the old one and is also supposedly ``improved,'' meaning that aside from containing a different number of bugs, it might improve your disk performance, especially if you have newer (EIDE-type) hardware. 4.3.3. Networking support (General Setup) In principle, you would only say `y' if your machine is on a network such as the internet, or you want to use SLIP, PPP, term, etc to dial up for internet access. However, as many packages (such as the X window system) require networking support even if your machine does not live on a real network, you should say `y'. Later on, you will be asked if you want to support TCP/IP networking; again, say `y' here if you are not absolutely sure. 4.3.4. System V IPC (General Setup) One of the best definitions of IPC (Interprocess Communication) is in the Perl book's glossary. Not surprisingly, some Perl programmers employ it to let processes talk to each other, as well as many other packages (DOOM, most notably), so it is not a good idea to say n unless you know exactly what you are doing. 4.3.5. Processor family (Processor type and features) (in older kernels: Use -m486 flag for 486-specific optimizations) Traditionally, this compiled in certain optimizations for a particular processor; the kernels ran fine on other chips, but the kernel was perhaps a bit larger. In newer kernels, however, this is no longer true, so you should enter the processor for which you are compiling the kernel. A ``386'' kernel will work on all machines. 4.3.6. SCSI support If you have SCSI devices, say `y'. You will be prompted for further information, such as support for CD-ROM, disks, and what kind of SCSI adapter you have. See the SCSI-HOWTO for greater detail. 4.3.7. Network device support If you have a network card, or you would like to use SLIP, PPP, or a parallel port adapter for connecting to the Internet, say `y'. The config script will prompt for which kind of card you have, and which protocol to use. 4.3.8. Filesystems The configure script then asks if you wish to support the following filesystems: Standard (minix) - Newer distributions don't create minix filesystems, and many people don't use it, but it may still be a good idea to configure this one. Some ``rescue disk'' programs use it, and still more floppies may have a minix filesystem, since the minix filesystem is less painful to use on a floppy. Second extended - This is the standard Linux filesystem. You almost definitely have one of these, and need to say `y'. msdos - If you want to use your MS-DOS hard disk partitions, or mount MS-DOS formatted floppy disks, say `y'. There are various other foreign operating system filesystem types available. /proc - (idea from Bell Labs, I guess). One doesn't make a proc filesystem on a disk; this is a filesystem interface to the kernel and processes. Many process listers (such as `ps') use it. Try `cat /proc/meminfo' or `cat /proc/devices' sometime. Some shells (rc, in particular) use /proc/self/fd (known as /dev/fd on other systems) for I/O. You should almost certainly say `y' to this; many important linux tools depend on it. NFS - If your machine lives on a network and you want to use filesystems which reside on other systems with NFS, say `y'. ISO9660 - Found on most CD-ROMs. If you have a CD-ROM drive and you wish to use it under Linux, say `y'. 4.3.8.1. But I don't know which filesystems I need! Ok, type `mount'. The output will look something like this: blah# mount /dev/hda1 on / type ext2 (defaults) /dev/hda3 on /usr type ext2 (defaults) none on /proc type proc (defaults) /dev/fd0 on /mnt type msdos (defaults) Look at each line; the word next to `type' is the filesystem type. In this example, my / and /usr filesystems are second extended, I'm using /proc, and there's a floppy disk mounted using the msdos (bleah) filesystem. You can try `cat /proc/filesystems' if you have /proc currently enabled; it will list your current kernel's filesystems. The configuration of rarely-used, non-critical filesystems can cause kernel bloat; see the section on modules for a way to avoid this and the ``Pitfalls'' section on why a bloated kernel is undesirable. 4.3.9. Character devices Here, you enable the drivers for your printer (parallel printer, that is), busmouse, PS/2 mouse (many notebooks use the PS/2 mouse protocol for their built-in trackballs), some tape drives, and other such ``character'' devices. Say `y' when appropriate. Note: gpm is a program which allows the use of the mouse outside of the X window system for cut and paste between virtual consoles. It's fairly nice if you have a serial mouse, because it coexists well with X, but you need to do special tricks for others. 4.3.10. Sound If you feel a great desire to hear biff bark, say `y', and you can tell the configuration program all about your sound board. (A note on sound card configuration: when it asks you if you want to install the full version of the driver, you can say `n' and save some kernel memory by picking only the features which you deem necessary.) If you are serious about sound card support, have a look at both the free drivers at http://www.linux.org.uk/OSS/ and the commercial Open Sound System at http://www.opensound.com/. 4.3.11. Other configuration options Not all of the configuration options are listed here because they change too often or fairly self-evident (for instance, 3Com 3C509 support to compile the device drive for this particular ethernet card). There exists a fairly comprehensive list of all the options (plus a way to place them into the Configure script) in an effort started and maintained by Axel Boldt (boldt@math.ucsb.edu) and it's the online help. It's also available as one big file at the Documentation/Configure.help in your Linux kernel source tree as of version 2.0. 4.3.12. Kernel hacking >From Linus' README: the ``kernel hacking'' configuration details usually result in a bigger or slower kernel (or both), and can even make the kernel less stable by configuring some routines to actively try to break bad code to find kernel problems (kmalloc()). Thus you should probably answer `n' to the questions for a ``production'' kernel. 4.4. Now what? (The Makefile) After you finish configuration, a message tells you that your kernel has been configured, and to ``check the top-level Makefile for additional configuration,'' etc. So, look at the Makefile. You probably will not need to change it, but it never hurts to look. You can also change its options with the `rdev' command once the new kernel is in place. If you're feel lost when you look at the file, then don't worry about it. 5. Compiling the kernel 5.1. Cleaning and depending When the configure script ends, it also tells you to `make dep' and (possibly) `clean'. So, do the `make dep'. This insures that all of the dependencies, such the include files, are in place. It does not take long, unless your computer is fairly slow to begin with. For older versions of the kernel, when finished, you should do a `make clean'. This removes all of the object files and some other things that an old version leaves behind. In any case, do not forget this step before attempting to recompile a kernel. 5.2. Compile time After depending and cleaning, you may now `make bzImage' or `make bzdisk' (this is the part that takes a long time.). `make bzImage' will compile the kernel, and leave a file in arch/i386/boot called `bzImage' (among other things). This is the new compressed kernel. `make bzdisk' does the same thing, but also places the new bzImage on a floppy disk which you hopefully put in drive ``A:''. `bzdisk' is fairly handy for testing new kernels; if it bombs (or just doesn't work right), just remove the floppy and boot with your old kernel. It can also be a handy way to boot if you accidentally remove your kernel (or something equally as dreadful). You can also use it to install new systems when you just dump the contents of one disk onto the other (``all this and more! NOW how much would you pay?''). All even halfway reasonably recent kernels are compressed, hence the `bz' in front of the names. A compressed kernel automatically decompresses itself when executed. In older kernels, you don't have the option to build a bzImage; it was simply a zImage. That option is at the moment still available, however, given the code size of newer kernels, it is now more or less mandatory to build a bzImage because the older methods can't handle a kernel that's just too large. 5.3. Other ``make''ables `make mrproper' will do a more extensive `clean'ing. It is sometimes necessary; you may wish to do it at every patch. `make mrproper' will also delete your configuration file, so you might want to make a backup of it (.config) if you see it as valuable. `make oldconfig' will attempt to configure the kernel from an old configuration file; it will run through the `make config' process for you. If you haven't ever compiled a kernel before or don't have an old config file, then you probably shouldn't do this, as you will most likely want to change the default configuration. See the section on modules for a description of `make modules'. 5.4. Installing the kernel After you have a new kernel that seems to work the way you want it to, it's time to install it. Most people use LILO (Linux Loader) for this. `make bzlilo' will install the kernel, run LILO on it, and get you all ready to boot, BUT ONLY if lilo is configured in the following way on your system: kernel is /vmlinuz, lilo is in /sbin, and your lilo config (/etc/lilo.conf) agrees with this. Otherwise, you need to use LILO directly. It's a fairly easy package to install and work with, but it has a tendency to confuse people with the configuration file. Look at the config file (either /etc/lilo/config for older versions or /etc/lilo.conf for new versions), and see what the current setup is. The config file looks like this: image = /vmlinuz label = Linux root = /dev/hda1 ... The `image =' is set to the currently installed kernel. Most people use /vmlinuz. `label' is used by lilo to determine which kernel or operating system to boot, and `root' is the / of that particular operating system. Make a backup copy of your old kernel and copy the bzImage which you just made into place (you would say `cp bzImage /vmlinuz' if you use `/vmlinuz'). Then, rerun lilo -- on newer systems, you can just run `lilo', but on older stuff, you might have to do an /etc/lilo/install or even an /etc/lilo/lilo -C /etc/lilo/config. If you would like to know more about LILO's configuration, or you don't have LILO, get the newest version from your favorite ftp site and follow the instructions. To boot one of your old kernels off the hard disk (another way to save yourself in case you screw up the new kernel), copy the lines below (and including) `image = xxx' in the LILO config file to the bottom of the file, and change the `image = xxx' to `image = yyy', where `yyy' is the full pathname of the file you saved your backup kernel to. Then, change the `label = zzz' to `label = linux-backup' and rerun lilo. You may need to put a line in the config file saying `delay=x', where x is an amount in tenths of a second, which tells LILO to wait that much time before booting, so that you can interrupt it (with the shift key, for example), and type in the label of the backup boot image (in case unpleasant things happen). 6. Patching the kernel 6.1. Applying a patch Incremental upgrades of the kernel are distributed as patches. For example, if you have version 1.1.45, 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 subdirecto­ ries 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. Additional packages Your linux kernel has many features which are not explained in the kernel source itself; these features are typically utilized through external packages. Some of the most common are listed here. 7.1. kbd The linux console probably has more features than it deserves. Among these are the ability to switch fonts, remap your keyboard, switch video modes (in newer kernels), etc. The kbd package has programs which allow the user to do all of this, plus many fonts and keyboard maps for almost any keyboard, and is available from the same sites that carry the kernel source. 7.2. util-linux Rik Faith (faith@cs.unc.edu) put together a large collection of linux utilities which are, by odd coincidence, called util-linux. These are now maintained by Andries Brouwer (util-linux@math.uio.no). Available via anonymous ftp from sunsite.unc.edu in /pub/Linux/system/misc, it contains programs such as setterm, rdev, and ctrlaltdel, which are relevant to the kernel. As Rik says, do not install without thinking; you do not need to install everything in the package, and it could very well cause serious problems if you do. 7.3. hdparm As with many packages, this was once a kernel patch and support programs. The patches made it into the official kernel, and the programs to optimize and play with your hard disk are distributed separately. 7.4. gpm gpm stands for general purpose mouse. This program allows you to cut and paste text between virtual consoles and do other things with a large variety of mouse types. 8. Some pitfalls 8.1. 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. 8.2. 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 lots 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'. 8.3. 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. 8.4. 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/. 8.5. 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.). 8.6. 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. 8.7. It says `warning: bdflush not running' This can be a severe problem. Starting with a kernel release after 1.0 (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. 8.8. I can't get my IDE/ATAPI CD-ROM drive to work Strangely enough, lots 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 linux in that versions 1.2.x don't support a third IDE interface (there is support in starting somewhere in the 1.3.x series but that's development, remember, and it doesn't auto- probe). 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. 8.9. 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. 8.10. Firewalling not working in 1.2.0 Upgrade to at least version 1.2.1. 8.11. ``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. 8.12. Problems with console terminal after upgrade to 1.3.x Change the word dumb to linux in the console termcap entry in /etc/termcap. You may also have to make a terminfo entry. 8.13. 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 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. 8.14. 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 9. Note for upgrade to version 2.0.x, 2.2.x Kernel versions 2.0.x and 2.2.x introduced quite a bit of changes for kernel installation. The file Documentation/Changes in the 2.0.x source tree contains information that you should know when upgrading to either of these versions. You will most likely need to upgrade several key packages, such as gcc, libc, and SysVInit, and perhaps alter some system files, so expect this. Don't panic, though. 10. 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. 10.1. Installing the module utilities The module utilities are available from wherever you got your kernel source as modutils-x.y.z.tar.gz; choose the highest patchlevel x.y.z that is equal to or below that of your current kernel. Unpack it with `tar zxvf modutils-x.y.z.tar.gz', cd to the directory it creates (modutils-x.y.z), look over the README, and carry out its installation instructions (which is usually something simple, such as make install). You should now have the programs insmod, rmmod, ksyms, lsmod, genksyms, modprobe, and depmod in /sbin. If you wish, test out the utilities with the ``hw'' example driver in insmod; look over the INSTALL file in that subdirectory for details. 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 mem­ ory, 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. 10.2. 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. 11. Tips and tricks 11.1. 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) 11.2. 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 run­ ning lilo, of course). The easiest way to tell LILO to boot a new ker­ nel 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. 11.3. 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.emlist.com in pub/kchanges or through the URL http://www.crynwr.com/kchanges 12. Other relevant HOWTOs that might be useful · 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 13. Misc 13.1. Author The author and maintainer of the Linux Kernel-HOWTO is Brian Ward (bri@cs.uchicago.edu). Please send me any comments, additions, corrections (Corrections are, in particular, the most important to me.). You can take a look at my `home page' at one of these URLs: http://www.math.psu.edu/bri/ http://blah.math.tu-graz.ac.at/~bri/ Even though I try to be attentive as possible with mail, please remember that I get a lot of it every day, so it may take a little time to get back to you. Especially when emailing me with a question, please try extra hard to be clear and detailed in your message. If you're writing about non-working hardware (or something like that), I need to know what your hardware configureation is. If you report an error, don't just say ``I tried this but it gave an error;'' I need to know what the error was. I would also like to know what versions of the kernel, gcc, and libc you're using. If you just tell me you're using this-or-that distribution, it won't tell me much at all. I don't care if you ask simple questions; remember, if you don't ask, you may never get an answer! I'd like to thank everyone who has given me feedback. If your question does not relate to the kernel, or is in some language that I don't understand, I may not answer. If you mailed me and did not get an answer within a resonable amount of time (three weeks or more), then chances are that I accidentally deleted your message or something (sorry). Please try again. I get a lot of mail about thing which are actually hardware problems or issues. That's OK, but please try to keep in mind that I'm not familiar with all of the hardware in the world. I use AMD processors, Adaptec and Sybios SCSI controllers, and IBM SCSI disks. Version -0.1 was written on October 3, 1994. This document is available in SGML, PostScript, TeX, roff, and plain-text formats. 13.2. To do The ``Tips and tricks'' section is a little small. I hope to expand on it with suggestions from others. So is ``Additional packages.'' More debugging/crash recovery info needed. 13.3. Contributions A small part of Linus' README (kernel hacking options) is inclusive. (Thanks, Linus!) uc@brian.lunetix.de (Ulrich Callmeier): patch -s and xargs. quinlan@yggdrasil.com (Daniel Quinlan): corrections and additions in many sections. nat@nat@nataa.fr.eu.org (Nat Makarevitch): mrproper, tar -p, many other things boldt@math.ucsb.edu (Axel Boldt): collected descriptions of kernel configuration options on the net; then provided me with the list lembark@wrkhors.psyber.com (Steve Lembark): multiple boot suggestion kbriggs@earwax.pd.uwa.edu.au (Keith Briggs): some corrections and suggestions rmcguire@freenet.columbus.oh.us (Ryan McGuire): makeables additions dumas@excalibur.ibp.fr (Eric Dumas): French translation simazaki@ab11.yamanashi.ac.jp (Yasutada Shimazaki): Japanese translation jjamor@lml.ls.fi.upm.es (Juan Jose Amor Iglesias): Spanish translation mva@sbbs.se (Martin Wahlen): Swedish translation jzp1218@stud.u-szeged.hu (Zoltan Vamosi): Hungarian translation bart@mat.uni.torun.pl (Bartosz Maruszewski): Polish translation donahue@tiber.nist.gov (Michael J Donahue): typos, winner of the ``sliced bread competition'' rms@gnu.ai.mit.edu (Richard Stallman): ``free'' documentation concept/distribution notice dak@Pool.Informatik.RWTH-Aachen.DE (David Kastrup): NFS thing esr@snark.thyrsus.com (Eric Raymond): various tidbits The people who have sent me mail with questions and problems have also been quite helpful. 13.4. Copyright notice, License, and all that stuff Copyright © Brian Ward, 1994-1999. Permission is granted to make and distribute copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the derived work is distributed under the terms of a permission notice identical to this one. Translations fall under the catagory of ``modified versions.'' Warranty: None. Recommendations: Commercial redistribution is allowed and encouraged; however, it is strongly recommended that the redistributor contact the author before the redistribution, in the interest of keeping things up-to-date (you could send me a copy of the thing you're making while you're at it). Translators are also advised to contact the author before translating. The printed version looks nicer. Recycle. 14. Other Formats of this Document This section is written by Al Dev (at site 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 - · 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 - · · · · · Other mirror sites near you (network-address-wise) can be found at 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 - and · Plain text format is in: and · Single HTML file format is in: 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 and 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 - 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) 14.1. 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 . 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. 14.2. 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 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 lots 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 run­ ning the perl script. For e.g. you may need to put closing tag < /Para> for each < Listitem> 14.3. 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. 14.4. 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 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 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.