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HP-UX System Administrator's Guide: Overview: HP-UX 11i Version 3 > Chapter 3 Major Components of HP-UX

The HP-UX Kernel


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The kernel is the central part of the HP-UX operating system; everything else around it depends on and interacts with. When you start up (boot) HP-UX, it is the kernel that is copied from disk into memory by the boot loader and initiated.

The kernel is made up of many subcomponents. In the case of an HP-UX kernel, these subcomponents are called kernel modules and kernel tunables.

Kernel Modules

Kernel modules are sections of kernel code dedicated to specific purposes, such as memory management, class drivers, or interface drivers.

Adding/Removing Kernel Modules

Many kernel modules are configured into the kernel when it is built and are always present in the kernel whenever it is running. Other modules are added when they are needed, and some can be removed when not needed.

The kernel modules that are only required some of the time fall into two categories:

  • Modules that can be added to, or removed from, the kernel while it is running

  • Modules that require a reboot to be added to, or removed from, the kernel

You can use the Modules tool in the Kernel Configuration toolbox in the System Management Homepage, or the kcmodule command from a shell command line, to:

  • view the current list of modules in the kernel,

  • view the state of specific modules in the kernel,

  • determine whether modules require a reboot to be added to or removed from the kernel,

  • change the state of a module, either currently (if supported by the module) or at the next boot.

For details about kernel configuration, see: “Configuring the Kernel” in HP-UX System Administrator’s Guide: Configuration Management.

Kernel Tunables

Kernel tunables are settings that determine things like how many processes can simultaneously be active or how much memory can be allocated for certain data structures within the kernel. For more information on kernel tunables, what they are, and how to adjust them, see the HP-UX System Administrator’s Guide: Configuration Management.

NOTE: Some kernel tunables have their values set at boot time and cannot be changed without rebooting. Other kernel tunables can be “tuned” (have their settings adjusted) while the kernel is running.
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