Terminology¶

Label¶

Example labels: Labels are key-value pairs assigned to Kubernetes Objects like Pods, Service

Example labels:

"release" : "stable", "release" : "canary"

Labels can be used to:

find all pods that have a value associated with the key
```
kubectl get pods -l key=val,key2=val2
```
merge and stream logs of the various pod that share the same label
```
kubectl logs -l key=val
```
apply filters to replica sets
```
kubectl get rs -l key=val
```

Label selectors¶

Unlike names and UIDs, labels do not provide uniqueness. In general, we many objects can have the same label.

Label selectors can be used to identify a set of objects. The label selector is the core grouping primitive in Kubernetes.

The API currently supports two types of selectors:

equality-based
- environment = production
- tier != frontend
set-based
- environment in (production, qa)
- tier notin (frontend, backend)
- partition
- !partition

Annotations¶

Annotations are used to store data about the resource itself

This usually consists of machine-generated data, and can even be stored in JSON form.

Examples:

last updated managed by sidecar injection configuration etc

ReplicaSet¶

A ReplicaSet's purpose is to maintain a stable set of replica Pods running at any given time. As such, it is often used to guarantee the availability of a specified number of identical Pods.

A ReplicaSet ensures that a specified number of pod replicas are running at any given time.

Deployment Strategies¶

kubectl abbreviations¶

Long Name	Short Name
services	svc
deployment	deploy