Documentation Relevant to Boot Diskettes & CD-ROMs

• HOW-TOs

  • Bootdisk-HOWTO

    This is the primary reference for making boot disks. It is difficult for beginners, but an essential document for anyone making their own boot disks.

    A few notes on this HOWTO:

    • The one-diskette version (boot/root) where one puts both the kernel and root filesystem on a single diskette is not worth the hassle. The two diskette (boot and root) arrangement is best.
    • Use the loopback method. It seems strange and complicated at first reading, but with the help of a couple of scripts, it is really quite easy and flexible. losetup is not needed.
    • I ignored the sections on PAM and NSS (at least for now).
    • For most systems, the full compressed kernel with all drivers built in (no modules) as well as the lilo files and "kernel filesystem" can easily fit on a single diskette. This simplifies the creation and use of the diskette set.
    • Don't worry about how the pros do it (section 9).

  • Kernel-HOWTO

    A guide to configuration and compilation of the Linux kernel

  • Lilo mini-Howto

    Useful examples of how to setup lilo.conf for 5 different situations.

  • CD-Writing-HOWTO

    A guide to the use of command-line Linux programs needed to write CD-ROMs.

• Special Documents

  • LILO Generic boot loader for Linux, Version 21 - Technical overview and User's Guide

    The Technical Overview is quite confusing, but the best documentation we have (other than the linux source code) for the structure of the linux kernel image and how it is loaded by Lilo.

    The User's Guide provides extensive documentation for the variety of command line and configuration options possible when using LILO.

  • linux/Documentation/devices.txt (or devices.tex)

    The official layout of /dev, specifying names and major/minor node values.

  • README.eltorito

    This is packaged with the CD writing program cdrecord

  • linux/Documentation/ramdisk.txt

    During boot, the kernel can preload ramdisk device /dev/ram0 (a.k.a. /dev/ram or /dev/ramdisk) from a floppy drive (/dev/fd0 or /dev/fd1) as specified by the kernel boot parameter root=... and make it the root device. This is the method used for loading the root filesystem in the two-diskette boot set.

    In newer kernels (2.2.12 or so and later) this feature is compatible with an initial ramdisk. Kernel boot parameter load_ramdisk=2 is then specified and the diskette filesystem is loaded into /dev/ram1 while the initial ramdisk is loaded into /dev/ram0. The initial ramdisk is initially mounted as root, and when it exits, the ramdisk loaded from the diskette(s) is mounted as root. Either can be compressed, but only an uncompressed, non-initial ramdisk can be can be loaded from multiple diskettes.

  • linux/Documentation/initrd.txt

    This document describes the creation and use of initial ramdisks. Additional clarifications may be obtained by examination of the source code in linux/init/main.c, linux/fs/super.c, linux/drivers/block/rd.c, and linux/drivers/block/genhd.c.

    The "initial ramdisk" must be loaded by the Lilo boot loader into memory from the device and blocks specified in the Lilo map file as a result of an initrd=... specification in lilo.conf. The initial ramdisk is temporarily mounted as the root filesystem, and a special file (program or shell script) in it, /initrdrc, is then run. When /initrdrc exits, the device specified by root=... in lilo.conf is then mounted as the final root filesystem.

    An "initial ramdisk" that remains as the permanent root filesystem is used for loading the root filesystem in the CD-ROM boot method.

• Books

  • Running Linux by Matt Welsh, Matthias Kalle Dalheimer & Lar Kaufman (O'Reilly Press, $35)

    This is an outstanding book to help beginners and intermediate users better understand the functioning and tuning of Linux. It has good under-the-hood type of information to help the user when simple user directions don't work. Most books simply give directions for how to use a system when it has already been properly configured.

  • Linux Core Kernel Commentary by Scott Maxwell (CoriolisOpen Press, $40)

    Source code listing for the core 40,000 lines of Linux kernel code plus well-worded commentary. An essential book for those who really want to understand Linux. It does not include many parts of Linux, but by studying this book, you will learn Linux coding styles and be better able to read the remaining source code.

• Man pages

  Note: "man -t xxx | lpr -Pps" or something similar prints hardcopy.

  lilo

  /sbin/lilo program and its command line options

  lilo.conf

  some of the specifications possible in the lilo.conf file

  initrd

  the operation of the ramdisk initialized by the boot loader.

  ram

  ramdisk device description (mine is an old, inadequate man page)

  rdev

  set kernel boot parameters - specifically the device with the root filesystem

  swapdev

  invocation of rdev -s that specifies the virtual memory swap device

  ramsize

  invocation of rdev -r that specifies if/how ramdisk is filled at boot (old man pages do not apply to newer kernels)

  vidmode

  invocation of rdev -v that sets the console video mode in kernel image

  rootflags

  invocation of rdev -R that sets rw/ro flag for root directory in kernel image

  bootparam

  description of kernel boot parameters

  inittab

  /etc/inittab run level specification file used by /sbin/init

  init

  /sbin/init program

  telinit

  alternate invocation of init program for changing runlevels

  mount -o loop

  filesystem mounting, needed for use with

  umount

  filesystem dismounting

  fstab

  /etc/fstab file specifying filesystem mount parameters

  dd

  dangerous, but crucial device-device copy program - use carefully

  cp -dpR

  recursively copy a directory and subdirectories preserving permissions and symbolic links (same as "cp -a")

  gzip

  compression program

  gunzip

  decompression invocation for gzip

  mke2fs -m 0

  layout a new filesystem on a device with no special reserved space

  mknod

  make device node for device

  chmod

  change permissions file or device

  chown

  change owner of file or device

  strip

  remove symbol info from object files to minimize their size

  ldd

  show library dependencies of an object file

  ldconfig

  setup library links and cache

  du

  determine amount of used disk space per file or directory

  df

  determine usage of entire filesystems

  chroot

  run a command or shell with an alternate root directory

  ln -s

  make a symbolic link to another file or directory

  stty

  set/show virtual terminal parameters

  agetty

  coordinate login and start shell (used with respawn in /etc/inittab)

  login

  login program

  sulogin

  single-user login

  update

  kernel daemon that handles disk caching

  locate

  find files using database maintained by updatedb

  updatedb

  update database for locate

  shutdown

  carefully shutdown system

  halt

  halt, reboot, or power-off the computer

  ctrlaltdel

  handle control-alt-del key signal response

  ps

  examine system tasks activity

  bash

  bash shell

• Notes concerning special RAM addresses and multi-byte storage

  • 0x00007c00 Address where BIOS puts boot sector
  • 0x00010000 Start of small Linux kernel (zImage)
  • 0x000a0000 Start of memory-mapped I/O address space
  • 0x000fffff End of memory-mapped I/O address space
  • 0x000fffff Top of 1st MB of memory
  • 0x00100000 Start of large Linux kernel (bzImage)
  • 0xffff0000 Start of BIOS address space
  • 0xfffffff0 Where processor looks for first instruction during boot
  • 0xffffffff Top of processor address space
  • Intel storage is little endian, e.g. the 16-bit word 0xaa55 when placed at RAM location 0x00fe has 0x55 at 0x00fe and 0xaa at 0x00ff.
  • Internet protocols are big endian, the most significant byte is at the specified RAM address, followed by the next most significant byte, etc..

Last updated: April 8, 2006