As a Linux user, I am sure you have come across the saying - Linux is just the kernel - and that all the tools (command line or otherwise) that come with it are bundled with it to make it the user friendly OS that it is . But what about other POSIX OSes like FreeBSD and Solaris ? Well, they are said to have the kernel and the command line tools more integrated with each other. But the difference doesn't end there. There are big differences in their respective kernels and how they accomplish a task.
Max Bruning has written a very good article which throws light on the differences (or rather the comparisons) of the kernels of these three OSes. He examines the three subsystems namely sheduling, memory management and file system architecture.
He arrives at the conclusion that kernel visibility and debugging tools play an important role in understanding the system better. Tools which help one to understand the kernel code are even more invaluable than just having access to the source code alone. On this note, he feels Solaris has a distinct advantage over Linux and FreeBSD because it comes with tools like kmdb, mdb and DTrace which help a developer to analyze the code better.