Manual Reference Pages - KLD (4)
- dynamic kernel linker facility
The LKM (Loadable Kernel Modules) facility has been deprecated in
and above in favor of the
This interface, like its
predecessor, allows the system administrator to dynamically add and remove
functionality from a running system.
This ability also helps software
developers to develop new parts of the kernel without constantly rebooting
to test their changes.
Various types of modules can be loaded into the system.
There are several defined module types, listed below, which can
be added to the system in a predefined way.
In addition, there
is a generic type, for which the module itself handles loading and
system makes extensive use of loadable kernel modules, and provides loadable
versions of most file systems, the
client and server, all the screen-savers, and the
modules are placed by default in the
directory along with their matching kernel.
interface is used through the
program can load either
or ELF formatted loadable modules.
program unloads any given loaded module, if no other module is dependent
upon the given module.
program is used to check the status of the modules currently loaded into the
Kernel modules may only be loaded or unloaded if the system security level
is less than one.
| Device Driver modules
New block and character device
drivers may be loaded into the system with
Device nodes for the loaded drivers are automatically created when a
module is loaded and destroyed when it is unloaded by
You can specify userland programs that will run when new devices
become available as a result of loading modules, or existing devices
go away when modules are unloaded, by configuring
directory containing module binaries built for the kernel also
residing in the directory.
file containing definitions required to compile a
example source code implementing a sample kld module
facility appeared in
and was designed as a replacement for the
facility, which was similar in functionality to the loadable kernel modules
facility provided by
facility was originally implemented by
.An Doug Rabson Aq dfr@FreeBSD.org .
If a module B, is dependent on another module A, but is not compiled with
module A as a dependency, then
fails to load module B, even if module A is already present in the system.
If multiple modules are dependent on module A, and are compiled with module
A as a dependency, then
loads an instance of module A when any of the modules are loaded.
If a custom entry point is used for a module, and the module is compiled as
fails to execute the entry point.
points the user to read
for any error encountered while loading a module.
When system internal interfaces change, old modules often cannot
detect this, and such modules when loaded will often cause crashes or
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