$ sudo apt-get update
$ sudo apt-get install hhvm-dbg 

hhvm-dbg is installed in your system.

Make ensure the hhvm-dbg package were installed using the commands given below,

$ sudo dpkg-query -l | grep hhvm-dbg *

You will get with hhvm-dbg package name, version, architecture and description in a table

hhvm-dbg package basic information: