(glossary)= # Glossary A partial glossary of terms used in this guide. For more complete descriptions of the components in JupyterHub, see {ref}`tools`. Here we try to keep the definition as succinct and relevant as possible, and provide links to learn more details. ```{glossary} [admin user](https://jupyterhub.readthedocs.io/en/stable/getting-started/authenticators-users-basics.html?highlight=admin) A user who can access the JupyterHub admin panel. They can start/stop user pods, and potentially access their notebooks. [authenticator](https://jupyterhub.readthedocs.io/en/stable/reference/authenticators.html) The way in which users are authenticated to log into JupyterHub. There are many authenticators available, like GitHub, Google, MediaWiki, Dummy (anyone can log in), etc. `config.yaml` The {term}`Helm charts ` templates are rendered with these {term}`Helm values` as input. The file is written in the [YAML](https://en.wikipedia.org/wiki/YAML) format. The YAML format is essential to grasp if working with Kubernetes and Helm. container A container is a isolated working space which for us gives users the tools, libraries, and capabilities to be productive. culler A separate process in the JupyterHub that stops the user pods of users who have not been active in a configured interval. Dockerfile A Dockerfile declares how to build a {term}`Docker image`. Docker image A Docker image, built from a {term}`Dockerfile`, allows tools like `docker` to create any number of {term}`containers `. image registry A service for storing Docker images so that they can be stored and used later. The default public registry is at https://hub.docker.com, but you can also run your own private image registry. Many cloud providers offer private image registry services. [environment variables](https://en.wikipedia.org/wiki/Environment_variable) A set of named values that can affect the way running processes will behave on a computer. Some common examples are `PATH`, `HOME`, and `EDITOR`. [Helm chart](https://helm.sh/docs/topics/charts/) A Helm chart is a group of {term}`Helm templates ` that can, given its default values and overrides in provided `yaml` files, render to a set of {term}`Kubernetes resources ` that can be easily installed to your Kubernetes cluster. In other words a Helm chart is like a configurable installation of software and infrastructure to exist on a cloud. [Helm template](https://helm.sh/docs/chart_template_guide/) A Helm template (`.yaml` files), can given values, render to a {term}`Kubernetes resource`. [Helm values](https://helm.sh/docs/chart_template_guide/values_files/) {term}`Helm charts ` has a set of predefined values (`values.yaml`) typically overridden by other values in `config.yaml`. The final values are used to generate {term}`Kubernetes resources ` from {term}`Helm templates ` within a {term}`Helm chart`. Kubernetes For our purposes, you can think of Kubernetes as a way to speak to a cloud and describe what you would like it to do, in a manner that isn't specific for that cloud. - [The Illustrated Children's Guide to Kubernetes](https://www.youtube.com/watch?v=4ht22ReBjno) - [The official "What is Kubernetes?" text](https://kubernetes.io/docs/concepts/overview/) Kubernetes API server The [Kubernetes API](https://kubernetes.io/docs/concepts/overview/kubernetes-api/) server, also referred to as the master, will answer questions and update the desired state of the cluster for you. When you use `kubectl` you communicate with the API server. Kubernetes Pod *Pods* are the smallest deployable units of computing that can be created and managed in Kubernetes. A pod will use a {term}`Docker image` to create a container, and most often a controller such as a Deployment will ensure there is always X running pods of a kind. See the [Kubernetes documentation](https://kubernetes.io/docs/concepts/workloads/pods/) for more information. Kubernetes resource A Kubernetes resource can for example be a [Deployment](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/), [Service](https://kubernetes.io/docs/concepts/services-networking/service/) or a [Secret](https://kubernetes.io/docs/concepts/configuration/secret/). It is something you can request by the {term}`Kubernetes API server` to be present in the cluster. persistent storage A filesystem attached to a user pod that allows the user to store notebooks and files that persist across multiple logins. Node Pool A *node pool* or *node group* represents a set of nodes of the same kind. With cluster autoscaling, a node pool can grow and shrink based on demand allowing you to save computational resources. [repo2docker](https://github.com/jupyterhub/repo2docker) A tool which lets you quickly convert a Git repository into a {term}`Docker image`. [spawner](https://jupyterhub.readthedocs.io/en/stable/getting-started/spawners-basics.html) A spawner is a separate process created for each active user by JupyterHub. They are each responsible for one user. This Helm chart relies on [KubeSpawner](https://jupyterhub-kubespawner.readthedocs.io/en/latest/). ```