.. glossary::
Alertmanager
The Alertmanager is a service for handling alerts sent by client
applications, such as :term:`Prometheus`.
See also the official Prometheus documentation for
`Alertmanager <https://prometheus.io/docs/alerting/alertmanager/>`_.
API Server
``kube-apiserver``
The Kubernetes API Server validates and configures data for the Kubernetes
objects that make up a cluster, such as :term:`Nodes <Node>` or
:term:`Pods <Pod>`.
|see K8s docs|
`kube-apiserver <https://kubernetes.io/docs/reference/command-line-tools-reference/kube-apiserver/>`_.
Bootstrap
Bootstrap node
The Bootstrap node is the first machine on which MetalK8s is installed,
and from where the cluster will be deployed to other machines. It also
serves as the entrypoint for upgrades of the cluster.
ConfigMap
A ConfigMap is a Kubernetes object that allows one to store general
configuration information such as environment variables in a key-value
pair format.
ConfigMaps can only be applied to namespaces and once created, they can
be updated automatically without the need of restarting containers that
depend on it.
|see K8s docs|
`ConfigMap <https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/#understanding-configmaps-and-pods/>`_.
Controller Manager
``kube-controller-manager``
The Kubernetes controller manager embeds the core control loops shipped
with Kubernetes, which role is to watch the shared state from
:term:`API Server` and make changes to move the current state towards
the desired state.
|see K8s docs|
`kube-controller-manager <https://kubernetes.io/docs/reference/command-line-tools-reference/kube-controller-manager/>`_.
``etcd``
``etcd`` is a distributed data store, which is used in particular for the
persistent storage of :term:`API Server`.
For more information, see `etcd.io <https://etcd.io>`_.
Environment
An Environment is a namespace or group of namespaces with specific labels
containing one or more Solutions.
It allows to run multiple instances of a Solution on the same cluster,
without collision between them.
Grafana
Grafana is a service for analysing and visualizing metrics scraped by
Prometheus.
For more information, see `Grafana <https://grafana.com/docs/grafana/latest/>`_.
Kubeconfig
A configuration file for :term:`kubectl`, which includes authentication
through embedded certificates.
|see K8s docs|
`kubeconfig <https://kubernetes.io/docs/concepts/configuration/organize-cluster-access-kubeconfig/>`_.
Kubelet
The kubelet is the primary "node agent" that runs on each cluster node.
|see K8s docs|
`kubelet <https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet/>`_.
Kube-state-metrics
The kube-state-metrics service listens to the Kubernetes API server and
generates metrics about the state of the objects.
|see K8s docs|
`kube-state-metrics <https://github.com/kubernetes/kube-state-metrics/tree/master/docs/>`_.
Loki
Loki is a log aggregation system designed to be cost-effective, only
indexing metadata (labels).
For more details, see `Loki documentation <https://grafana.com/docs/loki/latest/>`_.
Namespace
A Namespace is a Kubernetes abstraction to support multiple virtual
clusters backed by the same physical cluster, providing a scope for
resource names.
|see K8s docs|
`namespaces <https://kubernetes.io/docs/concepts/overview/working-with-objects/namespaces/>`_.
Node
A Node is a Kubernetes worker machine - either virtual or physical.
A Node contains the services required to run :term:`Pods <Pod>`.
|see K8s docs|
`Nodes <https://kubernetes.io/docs/concepts/architecture/nodes/>`_.
Node manifest
The YAML file describing a :term:`Node`.
|see K8s docs|
`Nodes management <https://kubernetes.io/docs/concepts/architecture/nodes/#management>`_.
Operator
A Kubernetes operator is an application-specific controller that extends
the functionality of the Kubernetes API to create, configure, and manage
instances of complex applications.
|see K8s docs|
`Operator <https://kubernetes.io/docs/concepts/extend-kubernetes/operator/>`_.
Pod
A Pod is a group of one or more containers sharing storage and network
resources, with a specification of how to run these containers.
|see K8s docs|
`Pods <https://kubernetes.io/docs/concepts/workloads/pods/pod/>`_.
Prometheus
Prometheus serves as a time-series database, and is used in MetalK8s as
the storage for all metrics exported by applications, whether being
provided by the cluster or installed afterwards.
For more details, see `prometheus.io <https://prometheus.io>`_.
Prometheus Node-exporter
The Prometheus node-exporter is an exporter for exposing hardware and
OS metrics read from the Linux Kernel. Users can typically obtain the
following metrics; cpu, memory, filesystem for each Kubernetes node.
For more details, see `prometheus node-exporter <https://prometheus.io/docs/guides/node-exporter>`_.
SaltAPI
SaltAPI is an HTTP service for exposing operations to perform with a
:term:`Salt Master`. The version deployed by MetalK8s is configured to
use the cluster authentication/authorization services.
|see Salt docs|
`SaltAPI <https://docs.saltstack.com/en/latest/ref/netapi/all/salt.netapi.rest_cherrypy.html#a-rest-api-for-salt>`_.
Salt Master
The Salt Master is a daemon responsible for orchestrating infrastructure
changes by managing a set of :term:`Salt Minions <Salt Minion>`.
|see Salt docs|
`Salt Master <https://docs.saltstack.com/en/latest/topics/development/architecture.html#salt-master>`_.
Salt Minion
The Salt Minion is an agent responsible for operating changes on a system.
It runs on all MetalK8s nodes.
|see Salt docs|
`Salt Minion <https://docs.saltstack.com/en/latest/topics/development/architecture.html#salt-minion>`_.
Scheduler
``kube-scheduler``
The Kubernetes scheduler is responsible for assigning :term:`Pods <Pod>`
to specific :term:`Nodes <Node>` using a complex set of constraints and
requirements.
|see K8s docs|
`kube-scheduler <https://kubernetes.io/docs/reference/command-line-tools-reference/kube-scheduler/>`_.
Secret
Kubernetes Secrets let you store and manage sensitive information,
such as passwords, OAuth tokens, and SSH keys.
|see K8s docs|
`Secrets <https://kubernetes.io/docs/concepts/configuration/secret/>`_.
Service
A Kubernetes Service is an abstract way to expose an application running
on a set of :term:`Pods <Pod>` as a network service.
|see K8s docs|
`Services <https://kubernetes.io/docs/concepts/services-networking/service/>`_.
Taint
Taints are a system for Kubernetes to mark :term:`Nodes <Node>` as
reserved for a specific use-case. They are used in conjunction with
:term:`tolerations <Toleration>`.
|see K8s docs|
`taints and tolerations <https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/>`_.
Toleration
Tolerations allow to mark :term:`Pods <Pod>` as schedulable for all
:term:`Nodes <Node>` matching some *filter*, described with
:term:`taints <Taint>`.
|see K8s docs|
`taints and tolerations <https://kubernetes.io/docs/concepts/configuration/taint-and-toleration/>`_.
``kubectl``
|kubectl| is a CLI interface for interacting with a Kubernetes cluster.
|see K8s docs| |kubectl|_.