Public Cloud
Public Cloud
This domain tests the OpenStack-based Public Cloud model: projects, regions, instances, storage, networking and billing. You should know what a project is and which objects live inside a region.
Projects and access
A project is the resource container and the billing boundary; deleting it deletes its resources. Underneath, OpenStack services handle compute (Nova), networking (Neutron), block storage (Cinder), object storage (Swift) and identity (Keystone). You can drive it from the OVHcloud control panel, Horizon, the OpenStack CLI/API or Terraform.
Instances and storage
Flavours are grouped by profile: general purpose, compute-optimised, memory-optimised, storage/IO-optimised and GPU. Instances are region-scoped and billed hourly, with a monthly cap option. Images come from public distributions, your own uploads, or snapshots. Volumes are block devices bound to one region and can be snapshotted.
Networking
Instances can be placed on a public network or on a private network with a subnet. Private-only instances need a router with a gateway and a floating IP to be reachable. Security groups are stateful and attach to ports.
Worked example
An instance on a private subnet must accept SSH from the internet and serve HTTPS. Create the network and subnet, attach a router to the external network, associate a floating IP with the instance port, then add a security group allowing TCP 22 and 443 inbound. Reasoning: private subnet → router; external reachability → floating IP; filtering → security group rather than guest firewall alone.
Traps
Quotas are per project and block creation silently. Volumes cannot be attached across regions. A floating IP must be associated, not merely allocated. Snapshots cost money and are not images by default.