title: freebsd kernel module - "make" command: unable to locate the kernel source tree. Set SYSDIR to override
body: <p>I am newbie in freebsd. I installed freebsd on VMware. I want to write first freebsd kernel module. I find this link: <a href="https://www.rhyous.com/2011/11/08/how-to-write-a-freebsd-kernel-module/" rel="nofollow noreferrer">How to write a FreeBSD Kernel Module</a></p>
  
  <p>But in step3, after <strong>make</strong> command I get:
  <em>unable to locate the kernel source tree. Set SYSDIR to override.</em> </p>
  
  <p>What is the output of <strong>make</strong> command?
  What should I do now?</p>