Module/kernel parameters

Tue, 20 Nov 2007 20:58:00 +0000

Sometimes it’s desirable to pass some arguments to module to customize its behavior, e.g.: to set/unset verbosity level of debug output, set operation mode etc… Linux modules can get this information from insmod utility, but kldload is not capable of doing such kind of things. What a pity. But don’t get desperate - tunables to the rescue!

Just like an ordinary command shell (bash, csh, sh) kernel has its own environment, the set of <name, value> pairs. You can get, set, test, unset these variables using getenv, setenv, testenv, unsetenv functions in the kernel and kenv(2) syscall or kenv(1) command in userland. So if you want to set verbosity level for module, you would do something like this:

Module Parameters on FreeBSD developer's notebook

Module/kernel parameters