Documentation/arch/m68k/kernel-options.rst

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===================================
Command Line Options for Linux/m68k
===================================

Last Update: 2 May 1999

Linux/m68k version: 2.2.6

Author: Roman.Hodek@informatik.uni-erlangen.de (Roman Hodek)

Update: jds@kom.auc.dk (Jes Sorensen) and faq@linux-m68k.org (Chris Lawrence)

0) Introduction
===============

Often I've been asked which command line options the Linux/m68k
kernel understands, or how the exact syntax for the ... option is, or
... about the option ... . I hope, this document supplies all the
answers...

Note that some options might be outdated, their descriptions being
incomplete or missing. Please update the information and send in the
patches.


1) Overview of the Kernel's Option Processing
=============================================

The kernel knows three kinds of options on its command line:

  1) kernel options
  2) environment settings
  3) arguments for init

To which of these classes an argument belongs is determined as
follows: If the option is known to the kernel itself, i.e. if the name
(the part before the '=') or, in some cases, the whole argument string
is known to the kernel, it belongs to class 1. Otherwise, if the
argument contains an '=', it is of class 2, and the definition is put
into init's environment. All other arguments are passed to init as
command line options.

This document describes the valid kernel options for Linux/m68k in
the version mentioned at the start of this file. Later revisions may
add new such options, and some may be missing in older versions.

In general, the value (the part after the '=') of an option is a
list of values separated by commas. The interpretation of these values
is up to the driver that "owns" the option. This association of
options with drivers is also the reason that some are further
subdivided.


2) General Kernel Options
=========================

2.1) root=
----------

:Syntax: root=/dev/<device>
:or:     root=<hex_number>

This tells the kernel which device it should mount as the root
filesystem. The device must be a block device with a valid filesystem
on it.

The first syntax gives the device by name. These names are converted
into a major/minor number internally in the kernel in an unusual way.
Normally, this "conversion" is done by the device files in /dev, but
this isn't possible here, because the root filesystem (with /dev)

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