11. Resources and pointers.

When retrieving a package, always get the latest version unless you have good reasons for not doing so.

11.1 Pre-made bootdisks.

These are sources for distribution bootdisks. Please use one of the mirror sites to reduce the load on these machines.

• Slackware bootdisks, rootdisks and Slackware mirror sites
• RedHat bootdisks and Red Hat mirror sites
• Debian bootdisks and Debian mirror sites

In addition to the distribution bootdisks, the following rescue disk images are available. Unless otherwise specified, these are available in the directory http://metalab.unc.edu/pub/Linux/system/recovery/!INDEX.html

• tomsrtbt, by Tom Oehser, is a single-disk boot/root disk based on kernel 2.0, with a large set of features and support programs. It supports IDE, SCSI, tape, network adaptors, PCMCIA and more. About 100 utility programs and tools are included for fixing and restoring disks. The package also includes scripts for disassembling and reconstructing the images so that new material can be added if necessary.

• rescue02, by John Comyns, is a rescue disk based on kernel 1.3.84, with support for IDE and Adaptec 1542 and NCR53C7,8xx. It uses ELF binaries but it has enough commands so that it can be used on any system. There are modules that can be loaded after booting for all other SCSI cards. It probably won't work on systems with 4 mb of ram since it uses a 3 mb ram disk.

• resque_disk-2.0.22, by Sergei Viznyuk, is a full-featured boot/root disk based on kernel 2.0.22 with built-in support for IDE, many difference SCSI controllers, and ELF/AOUT. Also includes many modules and useful utilities for repairing and restoring a hard disk.

• cramdisk images, based on the 2.0.23 kernel, available for 4 meg and 8 meg machines. They include math emulation and networking (PPP and dialin script, NE2000, 3C509), or support for the parallel port ZIP drive. These diskette images will boot on a 386 with 4MB RAM. MSDOS support is included so you can download from the net to a DOS partition.

  http://metalab.unc.edu/pub/Linux/system/recovery/images

11.2 Rescue packages.

Several packages for creating rescue disks are available on metalab.unc.edu. With these packages you specify a set of files for inclusion and the software automates (to varying degrees) the creation of a bootdisk. See http://metalab.unc.edu/pub/Linux/system/recovery/!INDEX.html for more information. Check the file dates carefully -- some of these packages have not been updated in several years and will not support the creation of a compressed root filesystem loaded into ramdisk. To the best of our knowledge, Yard is the only package that will.

11.3 Graham Chapman's shell scripts

Graham Chapman has written a set of scripts that may be useful as examples of how to create bootdisks. In previous versions of this HOWTO the scripts appeared in an appendix, but they have been deleted from the documented and placed on a web page:

http://www.zeta.org.au/~grahamc/linux.html

You may find it convenient to use these scripts, but if so, read the instructions carefully -- for example, if you specify the wrong swap device, you will find your root filesystem has been throroughly and permanently erased. Be sure you have it correctly configured before you use it!

11.4 LILO -- the Linux loader.

Written by Werner Almesberger. Excellent boot loader, and the documentation includes information on the boot sector contents and the early stages of the boot process.

Ftp from ftp://tsx-11.mit.edu/pub/linux/packages/lilo/. It is also available on Metalab and mirrors.

11.5 Linux FAQ and HOWTOs.

These are available from many sources. Look at the usenet newsgroups news.answers and comp.os.linux.announce.

The FAQ is available from http://linuxdoc.org/FAQ/Linux-FAQ.html and the HOWTOs from http://linuxdoc.org/HOWTO/HOWTO-INDEX.html. Most documentation for Linux may be found at The Linux Documentation Project homepage.

11.6 Ramdisk usage.

An excellent description of the how the new ramdisk code works may be found with the documentation supplied with the Linux kernel. See /usr/src/linux/Documentation/ramdisk.txt. It is written by Paul Gortmaker and includes a section on creating a compressed ramdisk.

11.7 The Linux boot process.

For more detail on the Linux boot process, here are some pointers:

• The Linux System Administrators' Guide has a section on booting, See http://linuxdoc.org/LDP/sag/c1596.html
• The LILO ``Technical overview'' http://metalab.unc.edu/pub/Linux/system/boot/lilo/lilo-t-21.ps.gz has the definitive technical, low-level description of the boot process, up to where the kernel is started.
• The source code is the ultimate guide. Below are some kernel files related to the boot process. If you have the Linux kernel source code, you can find these under /usr/src/linux on your machine; alternatively, Shigio Yamaguchi (shigio@tamacom.com) has a very nice hypertext kernel browser at http://www.tamacom.com/tour/linux/index.html. Here are some relevant files:

  arch/i386/boot/bootsect.S,setup.S

  Contain assembly code for the bootsector.

  arch/i386/boot/compressed/misc.c

  Contains code for uncompressing the kernel.

  arch/i386/kernel/

  Directory containing kernel initialization code. setup.c contains the ramdisk word.

  drivers/block/rd.c

  Contains the ramdisk driver. The procedures rd_load and rd_load_image load blocks from a device into a ramdisk. The procedure identify_ramdisk_image determines what kind of filesystem is found and whether it is compressed.