Wrote documentation and scripts for creating a busybox boot floppy. Initial revision.

examples/bootfloppy/bootfloppy.txt

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+Building a Busybox Boot Floppy
+==============================
+
+This document describes how to buid a boot floppy using the following
+components:
+
+ - Linux Kernel (http://www.kernel.org)
+ - uClibc: C library (http://cvs.uclinux.org/uClibc.html)
+ - Busybox: Unix utilities (http://busybox.lineo.com)
+ - Syslinux: bootloader (http://syslinux.zytor.com)
+
+It is based heavily on a paper presented by Erik Andersen at the 2001 Embedded
+Systems Conference.
+
+
+
+Building The Software Components
+--------------------------------
+
+Detailed instructions on how to build Busybox, uClibc, or a working Linux
+kernel are beyond the scope of this document. The following guidelines will
+help though:
+
+	- Stock Busybox from CVS or a tarball will work with no modifications to
+	  any files. Just extract and go.
+	- Ditto uClibc.
+	- Your Linux kernel must include support for initrd or else the floppy
+	  won't be able to mount it's root file system.
+
+If you require further information on building Busybox uClibc or Linux, please
+refer to the web pages and documentation for those individual programs.
+
+
+
+Making a Root File System
+-------------------------
+
+The following steps will create a root file system.
+
+ - Create an empty file that you can format as a filesystem:
+ 
+	dd if=/dev/zero of=rootfs bs=1k count=4000
+
+ - Set up the rootfs file we just created to be used as a loop device (may not
+   be necessary) 
+
+	losetup /dev/loop0 rootfs 
+
+ - Format the rootfs file with a filesystem:
+
+	mkfs.ext2 -F -i 2000 rootfs
+
+ - Mount the file on a mountpoint so we can place files in it:
+
+	mkdir loop
+	mount -o loop rootfs loop/
+
+	(you will probably need to be root to do this)
+
+ - Copy on the C library, the dynamic linking library, and other necessary
+   libraries. For this example, we copy the following files from the uClibc
+   tree:
+
+	mkdir loop/lib
+	(chdir to uClibc directory)
+	cp -a libc.so* uClibc*.so \
+		ld.so-1/d-link/ld-linux-uclibc.so* \
+		ld.so-1/libdl/libdl.so* \
+		crypt/libcrypt.so* \
+		(path to)loop/lib
+
+ - Install the Busybox binary and accompanying symlinks:
+
+	(chdir to busybox directory)
+	make PREFIX=(path to)loop/ install
+
+ - Make device files in /dev:
+
+ 	This can be done by running the 'mkdevs.sh' script. If you want the gory
+	details, you can read the script.
+
+ - Make necessary files in /etc:
+
+	For this, just cp -a the etc/ directory onto rootfs. Again, if you want
+	all the details, you can just look at the files in the dir.
+
+ - Run ldconfig so busybox and other binaries can have access to the libraries
+   that they need:
+
+   (path to)uClibc/ld.so-1/util/ldconfig -r loop/
+
+ - Unmount the rootfs from the mountpoint:
+
+	umount loop
+
+ - Compress it:
+
+	gzip -9 rootfs
+
+
+Making a SYSLINUX boot floppy
+-----------------------------
+
+The following steps will create the boot floppy.
+
+Note: You will need to have the mtools package installed beforehand.
+
+ - Insert a floppy in the drive and format it with an MSDOS filesystem:
+ 
+	mformat a:
+
+	(if the system doesn't know what device 'a:' is, look at /etc/mtools.conf)
+
+ - Run syslinux on the floppy:
+ 
+	syslinux -s /dev/fd0
+	
+	(the -s stands for "safe, slow, and stupid" and should work better with
+	buggy BIOSes; it can be omitted)
+
+ - Put on a syslinux.cfg file:
+
+	mcopy syslinux.cfg a:
+
+	(more on syslinux.cfg below)
+
+ - Copy the root file system you made onto the MSDOS formatted floppy
+
+	mcopy rootfs.gz a:
+
+ - Build a linux kernel and copy it onto the disk with the filename 'linux'
+
+	mcopy bzImage a:linux
+
+
+Sample syslinux.cfg
+~~~~~~~~~~~~~~~~~~~
+
+The following simple syslinux.cfg file should work. You can tweak it if you
+like.
+
+----begin-syslinux.cfg---------------
+DEFAULT linux
+APPEND initrd=rootfs.gz root=/dev/ram0
+TIMEOUT 10
+PROMPT 1
+----end-syslinux.cfg---------------
+
+Some changes you could make to syslinux.cfg:
+
+ - This value is the number seconds it will wait before booting. You can set
+   the timeout to 0 (or omit) to boot instantly, or you can set it as high as
+   10 to wait awhile.
+
+ - PROMPT can be set to 0 to disable the 'boot:' prompt.
+
+ - you can add this line to display the contents of a file as a welcome
+   message:
+
+	DISPLAY display.txt
+
+
+
+Additional Resources
+--------------------
+
+Other useful information on making a Linux bootfloppy is available at the
+following URLs:
+
+http://www.linuxdoc.org/HOWTO/Bootdisk-HOWTO/index.html
+http://www.linux-embedded.com/howto/Embedded-Linux-Howto.html
+http://linux-embedded.org/howto/LFS-HOWTO.html
+http://linux-embedded.org/pmhowto.html
+http://recycle.lbl.gov/~ldoolitt/embedded/ (Larry Doolittle's stuff)
+
+
+
+Possible TODOs
+--------------
+
+The following features that we might want to add later:
+
+ - support for additional filesystems besides ext2, i.e. minix
+ - different libc, static vs dynamic loading
+ - maybe using an alternate bootloader

examples/bootfloppy/display.txt

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+
+This boot floppy is made with Busybox, uClibc, and the Linux kernel.
+Hit RETURN to boot or enter boot parameters at the prompt below.
+

examples/bootfloppy/etc/fstab

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+proc		/proc	proc	defaults    0	0
+

examples/bootfloppy/etc/init.d/rcS

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+#! /bin/sh
+
+/bin/mount -a

examples/bootfloppy/etc/inittab

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+::sysinit:/etc/init.d/rcS
+::respawn:-/bin/sh
+tty2::askfirst:-/bin/sh
+::ctrlaltdel:/bin/umount -a -r
+

examples/bootfloppy/etc/profile

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+# /etc/profile: system-wide .profile file for the Bourne shells
+
+echo
+echo -n "Processing /etc/profile... "
+# no-op
+echo "Done"
+echo 
+

examples/bootfloppy/mkdevs.sh

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+#!/bin/sh
+#
+# makedev.sh - creates device files for a busybox boot floppy image
+
+
+# we do our work in the dev/ directory
+if [ -z "$1" ]; then
+	echo "usage: `basename $0` path/to/dev/dir"
+	exit 1
+fi
+
+cd $1
+
+
+# miscellaneous one-of-a-kind stuff
+mknod console c 5 1
+mknod full c 1 7
+mknod kmem c 1 2
+mknod mem c 1 1
+mknod null c 1 3
+mknod port c 1 4
+mknod random c 1 8
+mknod urandom c 1 9
+mknod zero c 1 5
+ln -s /proc/kcore core
+
+# IDE HD devs
+# note: not going to bother creating all concievable partitions; you can do
+# that yourself as you need 'em.
+mknod hda b 3 0
+mknod hdb b 3 64
+mknod hdc b 22 0
+mknod hdd b 22 64
+
+# loop devs
+for i in `seq 0 7`; do
+	mknod loop$i b 7 $i
+done
+
+# ram devs
+for i in `seq 0 9`; do
+	mknod ram$i b 1 $i
+done
+ln -s ram1 ram
+
+# ttys
+mknod tty c 5 0
+for i in `seq 0 9`; do
+	mknod tty$i c 4 $i
+done
+
+# virtual console screen devs
+for i in `seq 0 9`; do
+	mknod vcs$i b 7 $i
+done
+ln -s vcs0 vcs
+
+# virtual console screen w/ attributes devs
+for i in `seq 0 9`; do
+	mknod vcsa$i b 7 $i
+done
+ln -s vcsa0 vcsa

examples/bootfloppy/mkrootfs.sh

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+#!/bin/bash
+#
+# mkrootfs.sh - creates a root file system
+#
+
+# TODO: need to add checks here to verify that busybox, uClibc and bzImage
+# exist
+
+
+# command-line settable variables
+BUSYBOX_DIR=..
+UCLIBC_DIR=../../uClibc
+TARGET_DIR=./loop
+FSSIZE=4000
+CLEANUP=1
+MKFS='mkfs.ext2 -F'
+
+# don't-touch variables
+BASE_DIR=`pwd`
+
+
+while getopts 'b:u:s:t:Cm' opt
+do
+	case $opt in
+		b) BUSYBOX_DIR=$OPTARG ;;
+		u) UCLIBC_DIR=$OPTARG ;;
+		t) TARGET_DIR=$OPTARG ;;
+		s) FSSIZE=$OPTARG ;;
+		C) CLEANUP=0 ;;
+		m) MKFS='mkfs.minix' ;;
+		*)
+			echo "usage: `basename $0` [-bu]"
+			echo "  -b DIR  path to busybox direcory (default ..)"
+			echo "  -u DIR  path to uClibc direcory (default ../../uClibc)"
+			echo "  -t DIR  path to target direcory (default ./loop)"
+			echo "  -s SIZE size of root filesystem in Kbytes (default 4000)"
+			echo "  -C      don't perform cleanup (umount target dir, gzip rootfs, etc.)"
+			echo "          (this allows you to 'chroot loop/ /bin/sh' to test it)"
+			echo "  -m      use minix filesystem (default is ext2)"
+			exit 1
+			;;
+	esac
+done
+
+
+
+
+# clean up from any previous work
+mount | grep -q loop
+[ $? -eq 0 ] && umount $TARGET_DIR
+[ -d $TARGET_DIR ] && rm -rf $TARGET_DIR/
+[ -f rootfs ] && rm -f rootfs
+[ -f rootfs.gz ] && rm -f rootfs.gz
+
+
+# prepare root file system and mount as loopback
+dd if=/dev/zero of=rootfs bs=1k count=$FSSIZE
+$MKFS -i 2000 rootfs
+mkdir $TARGET_DIR
+mount -o loop,exec rootfs $TARGET_DIR # must be root
+
+
+# install uClibc
+mkdir -p $TARGET_DIR/lib
+cd $UCLIBC_DIR
+make INSTALL_DIR= 
+cp -a libc.so* $BASE_DIR/$TARGET_DIR/lib
+cp -a uClibc*.so $BASE_DIR/$TARGET_DIR/lib
+cp -a ld.so-1/d-link/ld-linux-uclibc.so* $BASE_DIR/$TARGET_DIR/lib 
+cp -a ld.so-1/libdl/libdl.so* $BASE_DIR/$TARGET_DIR/lib
+cp -a crypt/libcrypt.so* $BASE_DIR/$TARGET_DIR/lib
+cd $BASE_DIR
+
+
+# install busybox and components
+cd $BUSYBOX_DIR
+make distclean
+make CC=$BASE_DIR/$UCLIBC_DIR/extra/gcc-uClibc/i386-uclibc-gcc
+make PREFIX=bootfloppy/loop install
+cd $BASE_DIR
+
+
+# make files in /dev
+mkdir $TARGET_DIR/dev
+./mkdevs.sh $TARGET_DIR/dev
+
+
+# make files in /etc
+cp -a etc $TARGET_DIR
+ln -s /proc/mounts $TARGET_DIR/etc/mtab
+
+
+# other miscellaneous setup
+mkdir $TARGET_DIR/initrd
+mkdir $TARGET_DIR/proc
+$UCLIBC_DIR/ld.so-1/util/ldconfig -r $TARGET_DIR
+
+
+# Done. Maybe do cleanup.
+if [ $CLEANUP -eq 1 ]
+then
+	umount $TARGET_DIR
+	rmdir $TARGET_DIR
+	gzip -9 rootfs
+fi
+

examples/bootfloppy/mksyslinux.sh

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+#!/bin/bash
+#
+# Formats a floppy to use Syslinux
+
+dummy=""
+
+
+# need to have mtools installed
+if [ -z `which mformat` -o -z `which mcopy` ]; then
+	echo "You must have the mtools package installed to run this script"
+	exit 1
+fi
+
+
+# need an arg for the location of the kernel
+if [ -z "$1" ]; then
+	echo "usage: `basename $0` path/to/linux/kernel"
+	exit 1
+fi
+
+
+# need to have a root file system built
+if [ ! -f rootfs.gz ]; then
+	echo "You need to have a rootfs built first."
+	echo "Hit RETURN to make one now or Control-C to quit."
+	read dummy
+	./mkrootfs.sh
+fi
+
+
+# prepare the floppy
+echo "Please insert a blank floppy in the drive and press RETURN to format"
+echo "(WARNING: All data will be erased! Hit Control-C to abort)"
+read dummy
+
+echo "Formatting the floppy..."
+mformat a:
+echo "Making it bootable with Syslinux..."
+syslinux -s /dev/fd0
+echo "Copying Syslinux configuration files..."
+mcopy syslinux.cfg display.txt a:
+echo "Copying root filesystem file..."
+mcopy rootfs.gz a:
+# XXX: maybe check for "no space on device" errors here
+echo "Copying linux kernel..."
+mcopy $1 a:linux
+# XXX: maybe check for "no space on device" errors here too
+echo "Finished: boot floppy created"

examples/bootfloppy/quickstart.txt

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+Quickstart on making the Busybox boot-floppy:
+
+  1) Download Busybox and uClibc from CVS or tarballs. Make sure they share a
+     common parent directory. (i.e. busybox/ and uclibc/ are both right off of
+	 /tmp, or wherever.)
+
+  2) Build a Linux kernel. Make sure you include support for initrd.
+
+  3) Put a floppy in the drive. Make sure it is a floppy you don't care about
+     because the contents will be overwritten.
+
+  4) As root, type ./mksyslinux.sh path/to/linux/kernel from this directory.
+     Wait patiently while the magic happens.
+
+  5) Boot up on the floppy.

examples/bootfloppy/syslinux.cfg

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+display display.txt
+default linux
+timeout 10
+prompt 1
+label linux
+	kernel linux
+	append initrd=rootfs.gz root=/dev/ram0