Init hooks are for custom personal commands that the user may want to add to alter their boot. These can be used to load kernel modules, modify interfaces, and lot more. Those hooks are added to the /etc/init directory with the hook name as the suffix. For example, a boot script will be placed as /etc/init/my-hook.boot. Currently, there are 4 hooks that the user can use.
Run after pseudo-filesystems are mounted.
Run before the boot stage is completed.
Run first when shutting down.
Run just before the system is halted.