Installing VirtualBox on Dedicated Server

Hi,
I am trying to install VirtualBox on a dedicated server running CentOS (EL7). However, VirtualBox is unable to compile the required kernel extensions:

libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
libkmod: kmod_module_new_from_loaded: could not open /proc/modules: No such file or directory
Error: could not get list of modules: No such file or directory
This system is currently not set up to build kernel modules.
Please install the Linux kernel "header" files matching the current kernel
for adding new hardware support to the system.
This system is currently not set up to build kernel modules.
Please install the Linux kernel "header" files matching the current kernel
for adding new hardware support to the system.

This looks to be because the server is running a custom kernel so kernel-devel package won't match actual kernel. Can anyone suggest how VirtualBox can be installed on a dedicated server? Or even how kernel extensions may be installed?

Thanks!

Kind regards,
Matt