* Make hashboot executable
* Place hashboot anywhere in $PATH
* Install the appropriate init script
* If applicable, copy kernel-hook to /etc/kernel/post{inst,rm}.d/zzz-hashboot (make sure it is called after all other hooks)

VERIFIED TO WORK ON:
 * Gentoo (as of 2015/10)
 * Arch (as of 2015/10)

SHOULD WORK ON:
 * Systems with systemd init system
 * Systems with openrc init system
 * Systems with system v init system

WORKS NOT ON:
 * Ubuntu 14.04 (initscript.sysv doesn't interrupt boot process)
 * Systems with boot splash (I think)
 * Systems with openrc/sysv-init and parallel boot