Google Compute Engine offers scripts and daemons which run in the
background and provides the following services:

- Accounts daemon to setup and manage user accounts, and to enable SSH key based
  authentication.
- Clock skew daemon to keep the system clock in sync after VM start and stop
  events.
- Instance setup scripts to execute VM configuration scripts during boot.
- IP forwarding daemon that integrates network load balancing with forwarding
  rule changes into the guest.
- Metadata scripts to run user provided scripts at VM startup and shutdown.
- Network setup service to enable multiple network interfaces on boot.

WWW: https://github.com/GoogleCloudPlatform/compute-image-packages