Kernel and module parameters

Individual kernel parameters or module parameters are single keywords, or keyword-value pairs of the form keyword=<value> with no blank. Blanks separate consecutive parameters.

Kernel parameters and module parameters are encoded as strings of ASCII characters. For tape or the z/VM® reader as a boot device, the parameters can also be encoded in EBCDIC.

Use kernel parameters to configure the base kernel and any optional kernel parts that have been compiled into the kernel image. Use module parameters to configure separate kernel modules. Do not confuse kernel and module parameters. Although a module parameter can have the same syntax as a related kernel parameter, kernel and module parameters are specified and processed differently.

Separate kernel modules must be loaded before they can be used. This document describes module parameters as part of the syntax for loading the device driver or feature module to which they apply.

Where possible, this information describes kernel parameters with the device driver or feature to which they apply. Kernel parameters that apply to the base kernel or cannot be attributed to a particular device driver or feature are described in Selected kernel parameters. You can also find descriptions for most of the kernel parameters in Documentation/admin-guide/kernel-parameters.txt in the Linux source tree.

Which device drivers or features are compiled into the kernel or provided as separate modules can vary between distributions. This document describes both kernel and module parameters for device drivers or features that can be either separate modules or part of the kernel image.

When you want to configure a device driver or feature, check how your distribution includes this device driver or feature. Use kernel parameters or module parameters, accordingly. To find the separate kernel modules for your distribution, list the contents of the subdirectories of /lib/modules/<kernel-release> in the Linux file system. In the path, <kernel-release> denotes the kernel level. You can query the value for <kernel-release> with uname -r.