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1. Introduction

The kernel has a limited capability to accept information at boot in the form of a `command line', similar to an argument list you would give to a program. In general this is used to supply the kernel with information about hardware parameters that the kernel would not be able to determine on its own, or to avoid/override the values that the kernel would otherwise detect.

However, if you just copy a kernel image directly to a floppy, (e.g. cp zImage /dev/fd0) then you are not given a chance to specify any arguments to that kernel. So most Linux users will use software like LILO or loadlin that takes care of handing these arguments to the kernel, and then booting it.

IMPORTANT NOTE TO MODULE USERS: Boot Prompt arguments typically only apply to hardware drivers that are compiled directly into the kernel. They have no effect on drivers that are loaded as modules. Most distributions use modules. If you are unsure, then look at man depmod and man modprobe along with the contents of /etc/conf.modules.

This present revision covers kernels up to and including v2.0.33. Some features that are unique to development/testing kernels up to v2.1.84 are also documented.

The BootPrompt-Howto is by:

Paul Gortmaker,

[Please note that boot prompt arguments that are specific to the non-i386 ports and devices (esp. Atari/Amiga) are not currently documented.]

1.1 Disclaimer and Copyright

This document is not gospel. However, it is probably the most up to date info that you will be able to find. Nobody is responsible for what happens to your hardware but yourself. If your hardware goes up in smoke (...nearly impossible!) I take no responsibility. ie. THE AUTHOR IS NOT RESPONSIBLE FOR ANY DAMAGES INCURRED DUE TO ACTIONS TAKEN BASED ON THE INFORMATION INCLUDED IN THIS DOCUMENT.

This document is Copyright (C) 1995-1998 by Paul Gortmaker.

This document may be copied according to the conditions of the GNU General Public License, version 2, included herein by reference. See the file linux/COPYING that comes with the Linux kernel for full details.

If you are intending to incorporate this document into a published work, please contact me, and I will make an effort to ensure that you have the most up to date information available. In the past, out of date versions of the Linux howto documents have been published, which caused the developers undue grief from being plagued with questions that were already answered in the up to date versions.

1.2 Related Documentation

The most up-to-date documentation will always be the kernel source itself. Hold on! Don't get scared. You don't need to know any programming to read the comments in the source files. For example, if you were looking for what arguments could be passed to the AHA1542 SCSI driver, then you would go to the linux/drivers/scsi directory, and look at the file aha1542.c -- and within the first 100 lines, you would find a plain english description of the boot time arguments that the 1542 driver accepts.

The next best thing will be any documentation files that are distributed with the kernel itself. There are now quite a few of these, and most of them can be found in the directory linux/Documentation and subdirectories from there. The linux directory is usually found in /usr/src/. Sometimes there will be files that can be found in the related driver directory (e.g. linux/drivers/XXX/, where XXX will be scsi, char, or net).

If you have figured out what boot-args you intend to use, and now want to know how to get that information to the kernel, then look at the documentation that comes with the software that you use to boot the kernel (e.g. LILO or loadlin). A brief overview is given below, but it is no substitute for the documentation that comes with the booting software.

1.3 The Linux Newsgroups

If you have questions about passing boot arguments to the kernel, please READ this document first. If this and the related documentation mentioned above does not answer your question(s) then you can try the Linux newsgroups. Of course you should try reading the group before blindly posting your question, as somebody else may have already asked it, or it may even be a Frequently Asked Question (a FAQ). A quick browse of the linux FAQ before posting is a good idea. You should be able to find the FAQ somewhere close to where you found this document.

General questions on how to configure your system should be directed to the comp.os.linux.setup newsgroup. We ask that you please respect this general guideline for content, and don't cross-post your request to other groups.

1.4 New Versions of this Document

New versions of this document can be retrieved via anonymous FTP from the site, in the directory /pub/Linux/docs/HOWTO/. Note that SunSITE is usually heavily loaded, and you are better advised to get the document from one of the Linux ftp mirror sites. Updates will be made as new information and/or drivers becomes available. If this copy that you are presently reading is more than a few months old, then you should probably check to see if a newer copy exists.

This document was produced by using a modified SGML system that was specifically set up for the Linux Howto project, and there are various output formats available, including, postscript, dvi, ascii, html, and soon TeXinfo. I would recommend viewing it in the html (via a WWW browser) or the Postscript/dvi format. Both of these contain cross-references that are lost in the ascii translation.

If you want to get the official copy off sunsite, here is URL.


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