When you launch an instance from our cloud control panel, you'll see various boot source options. These images include several common Linux distributions labeled either "ISO" or "Cloud".
ISOs are official images provided by the respective Linux distros. Cloud images are essentially templates with additional packages and tweaks to optimize them for our OpenStack cloud environment. All of our cloud images have cloud-init included and preconfigured.
Choose your boot source based on how you want to install the operating system on your instance.
ISO - Traditional install. Requires selection of operating system options which allows for full customization.
Cloud Image - Instant install. The instance boots with the operating system installed. Customization possible with cloud-init user data.
See also: How do I use Cloud-Init User Data?