There are three ways to pass options to the kernel and thus control
its behavior:
This chapter describes the second method of passing options. The
chapter breaks the boot-time options into different logical sections.
A number of architecture-specific and individual driver options are
not listed here. For a complete list of all known options, please see
the file Documentation/kernel-parameters.txt in
the kernel source tree and the individual architecture-specific
documentation files.
Not all of the listed options are always available. Most are
associated with subsystems, and work only if the kernel is configured
with those subsystems built in. They also depend on the presence of
the hardware with which they are associated.
In addition to the options listed in this chapter, parameters for
modules that are built in to the kernel
can also be passed on the command line. (Dynamically loaded modules,
of course, are not in memory when the kernel boots and therefore
cannot be passed parameters at boot time.)
The syntax for passing parameters consisting of
the module name followed by a dot (.) and the
parameter.
For example, the
usbcore module accepts the parameter
blinkenlights to display flashing lights
on all supported USB 2.0 hubs (don't ever say the kernel developers
don't have a sense of humor). To set
this parameter when loading the module dynamically, you would enter:
$
modprobe usbcore blinkenlights=1
But if the usbcore module is built into the kernel,
you achieve the same effect by invoking the kernel with the following
option:
usbcore.blinkenlights=1
Most module options for modules that are built into the kernel can also be
changed at run time by writing to files in the subdirectory named after the
module under the /sys/module/ directory. Thus, the
blinkenlights option is represented by the file
/sys/module/usbcore/blinkenlights.
desired.
