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diff --git a/doc/uclibc-bootfloppy.txt b/doc/uclibc-bootfloppy.txt new file mode 100644 index 0000000..6dd4eff --- /dev/null +++ b/doc/uclibc-bootfloppy.txt @@ -0,0 +1,667 @@ +AUTHOR: Csaba Henk <ekho@math-inst.hu> + +DATE: 2003-10-27 + +LICENSE: The MIT License + +SYNOPSIS: Making an uClibc-based bootfloppy + +PRIMARY URI: http://www.math-inst.hu/~ekho/lowlife/ + +DESCRIPTION: +This hints shows how to create a cutting-edge bootfloppy from scratch, +based on uClibc, a lightweight C library. + +PREREQUISITES: +This hint should be useable on any not too aged Linux installation with +a non-broken toolchain. It was tested on a (by and large) LFS-4.0 +system. The sudo utility is advised to have. + +ATTACHMENTS: +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/busybox-0.60.5-Config.h +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/linux-2.4.22-.config +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/mkbootdisk +http://www.linuxfromscratch.org/patches/downloads/devfsd/devfsd-1.3.25-uclibc-1.patch + +HINT: + +Contents +-------- + +Preface +Introduction +What do we need? +The concept +Setting up the development environment +Compiling the linux kernel +Installing uClibc on the development platform +Creating the root filesystem +Installing uClibc for the bootdisk +Installing busybox +Installing gpm +Other programs +Creating the bootdisk +Bugs and weirdnesses, todo + +Preface +------- + +* This hint is co-developed with the svnc-thinclient hint in the +framework of the lowlife project, + +http://www.math-inst.hu/~ekho/lowlife/ + +This file belongs to lowlife-0.5.1. + +* For the most recent version check out + +http://www.math-inst.hu/~ekho/lowlife/uclibc-bootfloppy.txt + +* Comments, ideas, critics, flames are welcome. + +* (If you are an LFS user, you can skip this.) Although this document is +formally an LFS hint, you can see use of it without knowing what LFS is +(I tried to write it keeping this possibility in mind). Anyway, I +recommend you to check out what LFS is. If you are not familiar with +compiling source code in unix/linux environment, then there is no use of +going on without checking out what LFS is. Consult the following docs +first: + +http://www.linuxfromscratch.org/lfs/whatislfs.html +http://www.linuxfromscratch.org/faq/ +http://www.linuxfromscratch.org/hints/downloads/files/essential_prereading.txt +http://www.linuxfromscratch.org/lfs/view/stable/preface/prerequisites.html + +Introduction +------------ + +When you are to put together a Linux bootfloppy, you need to decide what +implementation of the standard C libraries will you use. + +One possibility is using the C library implementation which is common on +Linux based systems: glibc. It's advantage is that you have it at hand: +to make a glibc-based bootfloppy, the only thing you have to do is to is +to copy the necessary libs to the filesystem you will put on the floppy. +This is way chosen by the rescue floppy described in the BLFS-book: + +http://linuxfromscratch.org/blfs/view/test/postlfs/bootdisk.html + +However, glibc is far from being lightweight, and eats up much of the +rather limited space you have when working with a floppy. So you might +like seek for an alternative which suits much better to the capabilities +of the floppy environment. + +Here we will create a bootfloppy based on the uClibc C library, which is +just made for such purposes. + +The bootfloppy will be cutting edge: uses uClibc and Busybox which are +actively developed projects for the embedded platform. Moreover, I used +a kernel from the 2.4.* branch (but feel free to use other kernel +releases). It is a good question to ask whether this is useful: many floppy +distros use older kernels for reducing resource usage. I can say the +following: on the one hand, I can afford using a recent kernel as my +bootfloppy merrily runs on my 486 with 8M RAM; on the other hand, from +the moment I began to use this up-to-date stuff, the problems with handling +the terminal buffer and plip timeouts vanished. So unless you are really +tight in resources, I think using a recent kernel is a good idea. + +We will also use some kind of development environment, just to stay on +the safe side. + +This hint has a continuation: there we will describe how to install the +svga vncviewer on the bootfloppy, which then becomes capable of turning a +machine to an X terminal. (Check out the svnc-thinclient hint: + +http://www.linuxfromscratch.org/hints/downloads/files/svnc-thinclient.txt +http://www.math-inst.hu/~ekho/lowlife/svnc-thinclient.txt + +) + +Additional info and downloadable bootdisk image with svnc can be found +at the lowlife homepage (or at its mirror): + +http://www.math-inst.hu/~ekho/lowlife/ +http://www.personal.ceu.hu/students/01/Csaba_Henk/lowlife/ + +In this hint the assumption of using an x86 PC (both for making and +booting the floppy) and gcc is set. You may try to port it to another +architecture / compiler. Doing it on another architecture should not +be hard. Doing it with another compiler depends on how much does +uClibc support that compiler. + +If you copy command from this hint to your shell, be careful that +line-terminating backslashes (\) keep their position (no whitespace +characters should follow them). A possible solution is open this hint in +the Vim GUI, and copy'n'paste from there. + +What do we need? +---------------- + +We will need the following programs; in general, most recent stable +versions are recommended. Those programs where I have a certain +important comment on the version are marked with (!) and you can find +the comment at the beginning of the respective install instructons. + +* Addons for the development platform: + +sudo (optional) + ftp://ftp.sudo.ws/pub/sudo/ + +* Programs for the bootfloppy: + +linux-2.4.* (!) + http://www.kernel.org +uClibc + http://www.uclibc.org/downloads/ +busybox-0.60.5 (!) + http://www.busybox.net/downloads/ +gpm (optional) + ftp://arcana.linux.it/pub/gpm + +The concept +----------- + +In LFS, bootstrapping a linux system goes in the following fashion: one +first installs kernel headers, then builds a toolchain against these +headers, finally builds a kernel using the shiny new toolchain. + +We don't need to produce a new toolchain: we will use the one of the +host distro (to which we'll refer as "development environment") (though +when making the userspace of our tiny linux system, we will access that +toolchain via the uClibc wrappers). + +This lets us to proceed in a much simpler way: first we compile the +kernel, then build uClibc using the headers of this kernel, finally +build the userspace against uClibc. + +We will use optimization for size (we'll pass the -Os flag to gcc). In +general you can delete sources after compilation if there is no specific +reasons to keep them. In those cases when you should *not* delete the +source I'll tell about it explicitly. + +Setting up the development environment +-------------------------------------- + +We definitely need some kind of development environment to protect +us from mucking up our system; eg., if we are in the file system +which we will put on the floppy, it is very easy to mistake usr with +/usr, and without such a protection, you can imagine that this +mistake can have serious consequences... + +We will create a non-privileged user named bootdisk for doing the +job. First choose a home directory for bootdisk and store this value +in $BDISKHOME. Then type: + +groupadd bootdisk && +useradd -g bootdisk -s /bin/bash -d $BDISKHOME bootdisk && +mkdir -p $BDISKHOME && +cat > $BDISKHOME/.bash_profile << "EOF" +export CFLAGS=-Os +export PATH=/usr/i386-linux-uclibc/bin/:$PATH:$HOME/bin +export CC=i386-uclibc-gcc +EOF + +Of course, you may specify more cflags, like -march=i486. The above +setting of the $PATH variable assumes that the usual directories to +be contained in the path are already set in /etc/profile. + +So the idea is that we will work as user bootdisk; however, there are +some tasks during the bootdisk creation which require a privileged user +-- namely, mounting ext2 files and raw-copying to a floppy. + +We can do two things about this problem: + +1) Ignore it, and execute these tasks as root. + +2) Make a script named mkbootdisk for doing this tasks. This script must +be executable only by root (mode 744). With the help of the sudo utility +we let the bootdisk user to use this script as well. That is, we put it +to $BDISKHOME/bin and then type: + +echo " +bootdisk ALL = NOPASSWD: $BDISKHOME/bin/mkbootdisk" >> /etc/sudoers + +A realization of mkbootdisk can be found as an attachment of this hint +at + +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/ + +or at + +http://www.math-inst.hu/~ekho/lowlife/mkbootdisk + +or in the current directory if you read this hint as a file of the +lowlife tarball avaliable at + +http://www.math-inst.hu/~ekho/lowlife + +Typing "mkbootdisk -h" will print a brief information on usage. + +We have the desired environment. We go on compiling the programs. Become +user bootdisk: + +su - bootdisk + +In the rest of the hint we will act as user bootdisk, with the following +exceptions: + +* as uClibc will be installed systemwise, you should install it as root; + +* if you don't use a mkbootdisk script, then the appropriate actions +are to be done as root; + +* doing a chroot test of your filesystem for the floppy is possible only +as root. + +This means that if you use a mkbootdisk script, then those steps of +creating the bootfloppy which shouldn't affect your development +platform, *can't* affect the development platform (provided your +mkbootdisk script doesn't do anything weird, which I think is +fulfilled by the one written by me). + +Some of the commands below assume that the actual source archive is +decompressed in $HOME (which is the same as the prior $BDISKHOME). +Software installation instructions always start at the point when the +source tarball is already decompressed and you entered the source +directory (unless we explicitely claim to act differently). + +Compiling the linux kernel +-------------------------- + +At the moment the latest stable release of the linux kernel belong to +the 2.4.* branch, but 2.6.0-test* releases are already out. This +situaton might change any time by the release of linux-2.6.0. The +following instructions regard to the 2.4.* releases; if you want to try +linux-2.6.*, not only the kernel compilation instructions but the whole +bootdisk creation procedure is to be revised (eg., you can't boot a +2.6.* kernel without a boot loader). After linux-2.6.0 will be out I +might consider to upgrade this hint to that version. + +We will compile a network-aware kernel optimized to size. I don't give +a complete reference, I just highlight some crucial points.If you need +not network-awareness, you may omit TCP/IP netowrking and network +drivers; but even in this case it is strongly recommended to include +"Unix domain sockets". + +In the kernel source tree type: + +sed -e 's%-O2%-Os%g' -e '/^CFLAGS_KERNEL/s%\(^.*$\)%\1 -Os%' Makefile > \ + Makefile.tmp && +mv Makefile.tmp Makefile + +The above commands set optimization for size in the Makefile. Edit the +Makefile if you want further optimizations. + +Now you should configure the kernel with "make menuconfig". Choose +carefully the value in the "Processor type and features ---> Processor +family" menupoint. When choosing options, it is advised to include only +those features you really need. Some important ones: + +Networking options ---> + <*> Unix domain sockets + [*] TCP/IP networking + +In the "Network device support --->" menupoint choose those network +drivers you intend to use. If you want to use plip, choose it as a +module, and also set: + +Parallel port support ---> + <*> Parallel port support + <M> PC-style hardware + +This is advised because of the following: as I experienced, if no +option is given, the kernel initializes the parallel port (PC-style) +IRQ-less! At boot time we won't have the possibility to pass options +to the kernel, as we won't use a boot loader or initrd. Thus we can +set the appropriate IRQ value only if we load the parallel port +driver as module. Also, to gain more control over the NIC drivers, +consider building them as modules. + +In this hint we use the devfs facility, so choose + +File systems ---> + [*] /dev file system support + [*] Automatically mount at boot + +(See a more detailed description in the devfs hint: + +http://www.linuxfromscratch.org/hints/downloads/files/devfs+kernel_modules.txt + +). + +And don't forget to include support for the mouse type you will use with +the bootfloppy (if you will use any). + +OK, one more remark. Here I don't digress on how to use initrd, but you may +have some reason for doing that. In this case with some kernels (eg., with +linux-2.4.22) you might encounter with booting problems, which can be cured +by the appropriate kernel patch. For info on initrd and the patch you can +consult the "Creating a Custom Boot Disk" chapter of the BLFS-book, +referenced in the Introduction. + +Now compile the kernel with the + +make dep && make bzImage && make modules + +commands. Then type + +mkdir $HOME/rfloppy/lib/modules + +and copy the NIC driver modules from the drivers/net directory to +$HOME/rfloppy/lib/modules, and also the other modules you built. Eg., if +you use plip, you will need the drivers/parport/parport_pc.o +module. + +Do not delete the kernel source. + +If you have troubles with configuring the kernel properly, my .config file +might be of your help: + +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/ +http://www.math-inst.hu/~ekho/lowlife/linux-2.4.22/.config + +Installing uClibc on the development platform +--------------------------------------------- + +Usually we will optimize to size; in case of uClibc it's done +automatically. + +We install uClibc systemwise, thus the commands of this installation are +to be executed as root. + +In the uClibc source tree type + +make menuconfig + +uClibc now has a configuration interface similar to that of the linux +kernel. Apply the following settings: + +Target Architecture Features and Options ---> + ($BDISKHOME/<dir of your linux kernel for the floppy>) + Linux kernel header location +Library Installation Options ---> + (/lib) Shared library loader path + +This was enough for uClibc-0.9.19; in case of uClibc-0.9.21 we also need +the following: + +General Library Settings ---> + [ ] Support gprof profiling +String and Stdio Support ---> + [*] Support sys_siglist[] (bsd-compat) + +[Explanation: with profiling support set, uClibc wasn't willing to build +for me. The sys_siglist[] support will be needed by busybox which +encorporates some BSD code by having ash as its shell.] + +(Other uClibc versions may have their own gotchas.) + +Apart from this, the default configuration is quite suitable, probably +you need not change anything (especially you need not use full math +support). However, taking a look at the options never hurts; eg., you +may consider fine-tuning the target processor type. After you exit, + +make && +make install + +Further on we assume that you installed uClibc into +/usr/i386-linux-uclibc/ (the default installation location). + +Creating the root filesystem +---------------------------- + +We will put the files of the root filesysem of the floppy to a directory +named rfloppy. Firstly we create the directory and a basic tree of +subdirectories which vaguley resembles the FHS idea: + +cd && +mkdir -p rfloppy/{dev,proc,etc/init.d,sbin,bin,lib,mnt,usr,var/log} && +cat > rfloppy/etc/init.d/rcS << "EOF" && +#!/bin/sh +mount proc /proc -t proc +EOF + +The etc/init.d/rcS file will be the startup script for the floppy. Put +there what you want to be done in the beginnig -- eg., syslogd, klogd, +loading modules, starting gpm, etc. + +A very minimal etc directory is used in this setup. Enriching it (with +files like passwd, group, fstab, modules.conf, and so on) is up to you +-- this minimalist solution works anyway. + +Installing uClibc for the bootdisk +---------------------------------- + +We copy the necessary libraries of uClibc to the bootdisk. + +cp -a /usr/i386-linux-uclibc/lib/{ld-uClibc*,libc.so.0,libuClibc-*} \ + ~/rfloppy/lib + +Installing busybox +------------------ + +At the moment busybox has two branches: the development branch +(1.00-pre* releases) and the stable branch (0.60.* releases), but this +situation might change any time by busybox-1.00 being released. The +following instructions regard to the 0.60.* versions. The 1.00-pre* +versions differ greatly (encorporate much more utilities, eg.), so if +you go experimenting with them, these instructions probably need to be +changed. When the now-devel branch get stable (1.00 comes out), this +document will probably be upgraded to that version of busybox. + +Before making it, adjust the Config.h file according to your needs. To +make busybox work with devfs, be sure that the + +#define BB_FEATURE_DEVFS + +line is uncommented (not prefixed with "//"); and it is advised to +enable standard Unix utilities, moreover if you want to use network with +the floppy, consider uncommenting: + +#define BB_IFCONFIG +#define BB_TELNET +#define BB_TFTP +#define BB_FEATURE_IFCONFIG_STATUS + +Then install it with + +make CROSS=i386-uclibc- && +make PREFIX=$HOME/rfloppy install + +If you have troubles with configuring busybox properly, my Config.h file +might be of your help: + +http://www.linuxfromscratch.org/hints/downloads/attachments/uclibc-bootfloppy/ +http://www.math-inst.hu/~ekho/lowlife/busybox-0.60.5/Config.h + +Installing gpm +-------------- + +Having mouse at the console is not necessary, but very comfortable for a +bootfloppy as well. If you want it, install gpm by running the following +commands: + +./configure && +LDFLAGS="-lm" make && +strip src/gpm && +mkdir -p $HOME/rfloppy/{usr/sbin,var/run} && +cp src/gpm $HOME/rfloppy/usr/sbin && +cp -a /usr/i386-linux-uclibc/lib/{libm-*,libm.so.0} ~/rfloppy/lib + +[The /var/run directory is needed for gpm at runtime.] + +Other programs +-------------- + +Now if there is anything more you want to have on the floppy, compile it +and put it to the appropriate place under $HOME/rfloppy. A list of some +possible extensions: + +* devfsd ( + +http://ftp.kernel.org/pub/linux/daemons/devfsd/ + +) is not necessary for the bootfloppy, devfs work fine without it. So +install it only if you know what you are doing. However, it needs to be +hacked to get it compiled against uClibc. There is a patch for devfsd at: + +http://www.linuxfromscratch.org/patches/downloads/devfsd/devfsd-1.3.25-uclibc.patch + +or at + +http://www.math-inst.hu/~ekho/lowlife/patches/devfsd-1.3.25-uclibc.patch + +(or in the patches directory if you read this hint as a file of the lowlife +tarball) and you can find some explanation on it at + +http://www.math-inst.hu/~ekho/lowlife/ + +Note that devfsd depends on the libdl.so.0 library of uClibc (which is a +symlink to libdl-0.9.*.so). You have to put these to the /lib of your +filesystem. + +* The svnc-thinclient hint tells you how to compile and install svgalib +and the svga vncviewer to the floppy, giving the bootfloppy the +capabilities of an X terminal. + +The (functionality of the) following utilities are already encorporated +in the development versions of busybox. + +* You can put tinylogin ( + +http://tinylogin.busybox.net/ + +) to the floppy if you want a correct login system on it (with the +configuration described in this hint you just get a prompt after +booting). + +* You can put utelnetd ( + +http://www.pengutronix.de/software/utelnetd_en.html + +) to the floppy if you want to access it remotely. However, don't forget +that communication is not encrypted under telnet! + +* One more useful program is hdparm ( + +http://ftp.ibiblio.org/pub/Linux/system/hardware + +): if you boot with this floppy, the harddisk is probably not used, but +still is a source of noise by its spinning. You can stop it with +hdparm. (See its -y option.) + +Creating the bootdisk +--------------------- + +Before creating the floppy, you may wish to test the proposed filesystem +by chrooting to it; if so, execute as root: + +chroot $BDISKHOME/rfloppy /bin/sh + +Typing this you get the prompt of the busybox shell, and you should be +able to run those utilities which do not require much I/O (ls, cat, +echo,...). Proceed on again as the bootdisk user. + +Put a floppy to the floppy drive (if you are not sure about its +integrity, you might want to run fdformat on it). If you use my +mkbootdisk script, check whether the device name of the floppy drive is +set correctly in the script (it is set to /dev/fd0 and no option can +change it, in order to prevent the bootdisk user in being able to muck +up the development platform), and whether the $MKE2FSAPP, $RDEVAPP +variables in the script store the correct path to the mke2fs, rdev +utilities in your system (they should if you follow standards). If +everything is fine, simply run + +cd && +sudo mkbootdisk + +If you don't use the mkbootdisk script, become root, store the name of +your floppy device (typically /dev/fd0) in the variable $DISK. Now its +time to find out how big the root filesystem of the floppy should be, +and how much inodes should it have. Concerning the size, I think the +size of the stuff in the rfloppy directory + 150k is enough; concerning +the number of inodes, I think the number of files in rfloppy + 100 is +enough. But you should know. Store the chosen filesystem size in the +variable $SIZE (the number of kilobytes), and the chosen number of +inodes in the variable $INODES. Then type the following: + +cd $BDISKHOME && +# We we create and compress the root filesystem of the floppy: +dd if=/dev/zero of=rootfs bs=1k count=$SIZE && +yes | mke2fs -m 0 -N $INODES rootfs && +mkdir -p loop && +mount rootfs -o loop loop && +rmdir loop/lost+found && +cp -a rfloppy/* loop && +chown -R 0:0 loop/* && +umount loop && +dd if=rootfs bs=1k | gzip -v9 > rootfs.gz + +Now check whether rootfs.gz and your kernel image (probably +linux-2.4.*/arch/i386/boot/bzImage) fit on a floppy together (a floppy +is of 1440k usually but it can be formatted to bigger sizes as well). If +everything is fine, go on: + +# We copy the kernel to the floppy: +let KERNELSIZE=`dd bs=1k of=$DISK < linux-2.4.*/arch/i386/boot/bzImage 2>&1 | + sed -n '1s%\([0-9][0-9]*\).*%\1%p'`+1 && +# We perform some adjustments on the kernel copied to the floppy: +rdev $DISK 0,0 && +rdev -R $DISK 0 && +rdev -r $DISK `expr 16384 + $KERNELSIZE` && +# Finally we copy the compressed filesystem to its appropriate place \ +# on the floppy: +dd if=rootfs.gz of=$DISK bs=1k seek=$KERNELSIZE + +[Explanation -- also for those who wonder how the mkbootdisk script +works + +"yes | mke2fs -m 0 -N $INODES rootfs": + +This pipe construct is a common trick for answering stupid questions +non-interactively. + +"# We copy the kernel to the floppy" : + +In the command after this comment we not only copy the kernel to floppy, +but we also store the number of transferred kb's in the variable +$KERNELSIZE. + +"# We perform some adjustments on the kernel copied to the floppy" : + +We won't have a bootloader to tell the kernel where to find its root +filesystem. The commands after this comment set some specified bits +in the kernel, thus hardwiring the location of the root filesystem to +it: firstly, we tell the kernel to seek for the filesystem in the +floppy, secondly, we tell the kernel that a ramdisk is to be made and +the filesystem is to be decompressed to it, thirdly, we tell the +kernel the location of the filesystem within the floppy. The number +16384 = 2^14 is used for shifting within the range of bits in the +kernel devoted for describing these data. For more information +consult with the Bootdisk HOWTO available at tldp.org. + +"# Finally we copy [...]" : + +In the dd command after this comment we use the seek option to copy the +compressed filesystem nicely after the kernel image.] + +Now you have the floppy, boot & enjoy! + +Bugs and weirdnesses, todo +-------------------------- + +This hint is co-developed with the svnc-thinclient hint in the framework +of the lowlife project. These informations can be found in the svnc-thinclient +hint. + +ACKNOWLEDGEMENTS: + +This hint is co-developed with the svnc-thinclient hint in the framework +of the lowlife project. These informations can be found in the svnc-thinclient +hint. + +CHANGELOG: + +This hint is co-developed with the svnc-thinclient hint in the framework +of the lowlife project. These informations can be found in the svnc-thinclient +hint. |