The moddebug kernel variable controls the module loading process. The possible values of moddebug are:
Prints messages to the console when loading or unloading modules.
Gives more detailed error messages.
Prints more detail when loading or unloading, such as including the address and size.
No auto-unloading drivers. The system does not attempt to unload the device driver when the system resources become low.
No auto-unloading streams. The system does not attempt to unload the STREAMS module when the system resources become low.
No auto-unloading of kernel modules of any type.
If running with kmdb, moddebug causes a breakpoint to be executed and a return to kmdb immediately before each module's _init() routine is called. This setting also generates additional debug messages when the module's _info() and _fini() routines are executed.