113 lines
4.6 KiB
Markdown
113 lines
4.6 KiB
Markdown
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# Vocabulary
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https://kubernetes.io/docs/tutorials/kubernetes-basics/explore/explore-intro/ - Good summary of the different parts
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## Cluster
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The largest unit, a kubernetes cluster is a collection of one or more worker machines (virtual or physical machines), and the control plane.
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## Control plane
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A control plane is in charge of managing worker nodes and pods in a cluster.
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## Node
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[A node](https://kubernetes.io/docs/tutorials/kubernetes-basics/explore/explore-intro/) is a virtual or physical machine that in Kubernetes, and is managed by the control plane. A Node can have multiple pods, and the control plane is in charge of scheduling pods across nodes.
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Each node runs at least:
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- A Kubelet, the process responsible for handling communication between the control plane and the node. It manages the pods and containers running on a machine
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- A [container runtime](https://kubernetes.io/docs/setup/production-environment/container-runtimes/) responsible for pulling the container image from a registry, unpacking the container, and running the application. Examples include containerd and docker.
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## Deployment
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A [deployment](https://kubernetes.io/docs/tutorials/kubernetes-basics/deploy-app/deploy-intro/) instructs kubernetes how to create and update instances of an application. It can be imagined similar to a blueprint. The term 'deployment' may also refer to the group of pods and replicas defined by one or more configuration files.
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## Pod
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A [pod](https://kubernetes.io/docs/tutorials/kubernetes-basics/explore/explore-intro/) is an abstraction that represents a group of one or more application containers, and shared resources. Some shared include storage and a private network. They are meant to represent a logical host, and a rough parallel might be a physical machine running a service, although this machine may have multiple network adapters. A deployment creates pods, and not containers.
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## ReplicaSet
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A [ReplicaSet](https://kubernetes.io/docs/concepts/workloads/controllers/replicaset/), often referred to as a pod replica, is an identical copy of pod. They can be used for many things, most commonly high availability and load balancing.
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## Service
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A [service](https://kubernetes.io/docs/concepts/services-networking/service/) in Kubernetes is is an abstraction that defines a logical set of Pods and a policy to access them. A Service is defined using YAML or JSON, and is primarily used to expose a network application that's running on one or more Pods in a cluster. They also route traffic across a set of Pods, allowing Pods to die and replicate without impacting the application.
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## `kubectl`
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`kubectl` is the Kubernetes command line tool used to run commands against clusters. You can use `kubectl` to deploy applications, inspect and manage cluster resources, and view logs. The general format of the command follows `kubectl [action] [resource]`
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## `minikube`
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`minikube` creates a local Kubernetes cluster for development. It can be configured to deploy on bare metal, containers (like docker), or a VM (QEMU).
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# Commands
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## Common commands
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- **kubectl get** - list resources
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- **kubectl describe** - show detailed information about a resource
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- **kubectl logs** - print the logs from a container in a pod
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- **kubectl exec** - execute a command on a container in a pod
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## Start `minikube`
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```
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minikube start
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```
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## Stop `minikube`
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```
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minikube stop
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```
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## Expose services running in minikube
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```
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minikube services
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```
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## View the dashboard for `minikube`(run in new terminal window)
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```
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minikube dashboard
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```
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## Check that `kubectl` is configured to talk to the cluster
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```
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kubectl version
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```
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## View nodes in the server
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```
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kubectl get nodes
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```
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## List deployments
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```
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kubectl get deployments
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```
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## Start a proxy to access the private network
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```
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kubectl proxy
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```
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## Access the API of a pod (through the proxy)
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```
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curl http://localhost:8001/api/v1/namespaces/default/pods/$POD_NAME/
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```
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Where `$POD_NAME` is the name of a pod, you can get this information with `kubectl get pods`
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## Start a Bash session in a Pod's container
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```
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kubectl exec --ti $POD_NAME -- bash
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```
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## Create a new Service and expose it to external traffic
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```
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kubectl expose deployment/kubernetes-bootcamp --type="NodePort" --port 8080
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```
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## Apply a new label to pods
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```
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kubectl label pods "$POD_NAME" version=v1
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```
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## See if a Service is load-balancing traffic
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```
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kubectl describe services/$SERVICE_NAME
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```
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## Set a different desired amount of replicas for a deployment
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```
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kubectl scale deployments/$DEPLOYMENT_NAME --replicas=$DESIRED_NUM_OF_REPLICAS
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```
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# Tutorials
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https://kubernetes.io/docs/tutorials/hello-minikube/
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https://kubernetes.io/docs/tutorials/kubernetes-basics/
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