8.2 SunOS 5.X
You can customize the kernel with the /etc/system file. This configuration file contains commands to be read by the kernel during initialization. You can specify that modules be excluded, or loaded during initialization, rather than when first used, etc. You can set the root and swap devices to something other than the default value. You can even set the value of kernel parameters, e.g.:
set maxusers=16
Each type of module has it's own subdirectory in /kernel, e.g. the device drivers are under /kernel/drv. Each driver also has a configuration file associated with it to set the kernel parameter values. Solaris 2.5 and above again has a platform-independent set in /kernel/drv and a platform- dependent set in /platform/'uname -m'/kernel/drv.
A significant advantage to modularization is that the kernel now only loads the modules it needs, making more efficient use of memory. Also, you can add drivers without having to rebuild the kernel and reboot the system.