No offense intended, but if creating ~/unused (or some preferred alternative) is opaque to you, using EE, trying to run a server with HHVM, etc. is probably beyond your current skillset and you might want to back up a little bit and get some basic linux shell training.
That said,
HOW: you make a directory on the command line with the command mkdir
WHERE: is actually already in what I wrote because the ‘~’ is a shortcut in the linux shell for your home directory, so if you type mkdir ~/unused
you will create a directory called “unused” inside your home directory.
(But you might not want to keep it there. You can put it (the start script) anywhere you want or even just throw it away [ rm /etc/init.d/hhvm
]. The idea is just to get it out of /etc/init.d
so it won’t be executed by the system automatically. Again, all of this is basic linux shell / sysadmin stuff that you really need to already know if you are trying to set up and maintain a server with EE).