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diff --git a/examples/bootfloppy/bootfloppy.txt b/examples/bootfloppy/bootfloppy.txt new file mode 100644 index 000000000..575c93fcc --- /dev/null +++ b/examples/bootfloppy/bootfloppy.txt @@ -0,0 +1,185 @@ +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 |