Running Linux, Third Edition

Loading Modules Automatically

The so-called kernel daemon kerneld is an especially useful feature. With the help of this daemon, the kernel can load needed device drivers and other modules automatically and without manual intervention from the system administrator. If the modules are not needed after a period of time (60 seconds), they are automatically unloaded as well.

In order to use kerneld, you need to turn on support for it during kernel configuration, and you also need the System V IPC option. kerneld must be started from one of the system startup files; newer distributions are doing this automatically.

Modules that need other modules must be correctly listed into /lib/modules/ kernelversion /modules.dep, and there must be aliases for the major and minor number in /etc/conf.modules. See the documentation from the modules package for further information.

If a module has not been loaded manually with insmod or modprobe, but loaded automatically from kerneld, the module is listed with the addition (autoclean) in the lsmod output. This tells you that kerneld will remove the module if it has not been used for more than one minute.

One last word about kerneld: In the latest kernels, kerneld is obsolete, because there is a new kernel feature called kmod that does the same (by running a separate kernel thread that loads the modules on demand). Still, running kerneld does not hurt.