## Glossary This glossary defines common terms used throughout the RunAtlas cloud platform. ### A - **Account**: The administrative entity that owns resources (instances, networks, volumes) and is billed monthly. - **Availability Zone (AZ)**: Isolated data center location within a Region designed to minimize failure impact. ### C - **Cluster**: A group of Host nodes (physical servers) managed as a single pool of resources. - **Compute Offering**: defines CPU and RAM allocations for an Instance (e.g., Small, Medium, Large). - **Core**: A virtual CPU (vCPU) allocated to an instance. ### D - **Disk Offering**: Defines the size and performance characteristics (IOPS) of a Data Volume. - **Data Volume**: Additional storage attached to an instance, separate from the Operating System (Root) disk. ### E - **Elastic IP (EIP)**: A static public IP address that can be remapped between instances. - **Egress Rule**: Firewall rule controlling outbound traffic from a network. ### G - **Guest Network**: An isolated virtual network (VLAN/VXLAN) dedicated to a single account. - **Gateway**: The router interface providing connectivity for a network. ### H - **Host**: Physical server running the hypervisor (KVM) where instances reside. - **Hypervisor**: Software (KVM) that creates and runs virtual machines. ### I - **Image / Template**: A pre-configured operating system image (e.g., Ubuntu, CentOS) used to launch instances. - **Instance**: A Virtual Machine (VM). - **Ingress Rule**: Firewall rule controlling inbound traffic to a network. ### K - **Key Pair**: SSH public/private keys used for secure instance authentication. ### N - **Network**: The connectivity layer (L2/L3) for instances. See [[Guest Networks]]. - **Network ACL**: Stateless firewall rules operating at the subnet level in a VPC. ### P - **Port Forwarding**: Mapping an external public port to an internal private IP/port. - **Public IP**: A globally routable IPv4 address. - **Project**: A logical grouping of resources and users for collaborative management. ### R - **Region**: A geographic area containing multiple Availability Zones. - **Root Volume**: The primary disk containing the OS of an instance. - **Router (Virtual Router)**: A system VM managing network services (DHCP, DNS, NAT, VPN, Firewall) for a Guest Network. ### S - **Security Group**: Stateful firewall rules applied directly to an instance's network interface. - **Snapshot**: A point-in-time backup of a Volume. - **Source NAT**: The primary public IP used for outbound traffic from a private network. - **Static NAT**: 1-to-1 mapping of a Public IP to a Private IP. ### T - **Template**: System image used to create new VMs. - **Tier**: A logical subnet within a VPC (e.g., Web Tier, App Tier). ### U - **User Data**: Scripts or cloud-init configuration passed to an instance at launch. ### V - **VLAN**: Virtual Local Area Network; L2 isolation mechanism. - **VM**: Virtual Machine; see Instance. - **Volume**: A virtual hard disk (standard or SSD). - **VPC (Virtual Private Cloud)**: An isolated network environment with user-defined subnets, routes, and gateways. - **VPN**: Virtual Private Network; secure connection logic.