The contents of the kernel, which were formerly in a single file, /vmunix, are now contained in modules in a directory hierarchy. By default, the directory hierarchy is/platform/'uname -i'/kernel, /kernel, and /usr/kernel.
The directory search path for modules can be set by the
moddir variable in the /etc/system file (see the system(4) man page). Typically, /platform/'uname -i'/kernel/unix is the first portion of the kernel to be loaded (see the kernel(1M) man page).