Kubernetes Glossary

DigitalOcean Kubernetes (DOKS) is a managed Kubernetes service. Deploy Kubernetes clusters with a fully managed control plane, high availability, autoscaling, and native integration with DigitalOcean Load Balancers and volumes. DOKS clusters are compatible with standard Kubernetes toolchains and the DigitalOcean API and CLI.

This glossary defines the core concepts behind Kubernetes to help build your mental model of how Kubernetes work and understand what the documentation is referring to when it uses certain terminology.

Cluster networking is highly-coupled container-to-container, pod-to-pod, pod-to-service, or external-to-service communication.
A central processing unit, also called a processor or CPU, is an essential piece of computer hardware that executes the instructions from a computer program.
An environment variable is a in-memory key/value pair that developers use to store configuration details about their app.
Feature gates are key-value pairs that describe upstream Kubernetes features.

A hash is a fixed-sized string created by applying a hash function to data. A hash can be used in many different applications for various purposes but are often used to encrypt SSH keys or create unique numerical values that can act as identifiers for data resources.

For example, hashes are used to reference code changes, called commits, in GitHub and other code repository services. DigitalOcean’s Container Registry also uses hashes to create digests for each version of an image stored in a registry. An example hash created with the SHA algorithm looks like this: 3479436528b6961f29e22576d76787b6e5262761

A health check is a scheduled HTTP or TCP request that you can configure to run on a repeating basis to ensure that a service is healthy.
High Availability (HA) is an approach to infrastructure design focusing on reducing downtime and eliminating single points of failure.
High-availability control plane is a control plane that has multiple replicas of each control plane component.
A container image, Docker image, or image, is a static file containing executable code that cannot be changed.
The Internet Protocol (IP) is a communications protocol used to connect computers across a network, specifically the Internet. IP consists of rules and regulations for transmission of packets across a network including routing and addressing. IP ensures that the packets of data that travel across a network arrives at the correct location.
Keep-Alive, or keepalive, is a signal sent from one device to another in order to maintain the connection between the two devices.
kubectl is a command-line interface (CLI) used to run commands on Kubernetes clusters.
A load balancer distributes traffic across a backend pool of servers to improve the stability and responsiveness of an application.
Logs are captures of the standard output stream that you can inspect for information about activity related to your app.
Machine type is the set of virtualized hardware resources used for a virtual machine (VM) instance.
A namespace is a collection of resources containing one or more functions hosted on the DigitalOcean Functions service.
Node plan, database or cluster configuration is the hardware plan for node specifications.
A node pool is a group of nodes with the same configuration within a cluster.
A pod is the smallest deployable unit of computing that is created and managed by Kubernetes.
A port is a communication endpoint of a network connection. A port is identified using a port number for each transport protocol.
A proxy is a computer or software system that acts as a dedicated intermediary between an endpoint device and another server.
Role-based access control (RBAC), also known as role-based security, restricts network access based on the role a user has within an organization.
SSL certificate is a digital document outlining the identity of the website.
Sticky session, or session persistence occurs when the load balancer creates a connection between a network and a user for a direction of the session.
Surge upgrades create duplicate, up to a maximum of 10, nodes during cluster upgrade.
Tags are keywords associated with resources which help with managing resource ownership and organize lookups and actions on resources.
The Transmission Control Protocol (TCP) is a communication standard for programs and computing devices to exchange messages over a network.
TTL, also known as time to live or hop limit, is the amount of time (also called hops) that a packet exists before being discarded by a router. TTL limits the lifespan of data within a network through attaching a time limit to data.
User Datagram Protocol, or UDP, is an established low-latency connection communication protocol between applications.
A worker node is a node that runs the application in a cluster and reports to a control plane.