Shared folders with Virtualbox and Centos 7

Got a build error with VirtualBox add-ins and HDP Sandbox 2.2.

Building the main Guest Additions module   [FAILED]

Fixed by checking the log file for errors,  Missing kernel directory issue.

$ export KERN_DIR=/lib/modules/2.6.32-504.1.3.el6.x86_64/

$ cd /usr/src/kernels

$ ln -s /usr/src/kernels/2.6.32-573.7.1.el6.x86_64/ 2.6.32-504.1.3.el6.x86_64