Can somene explain the different Kubernetes yaml files and types?

2/7/2020

First off, I'm completely new with Kubernetes so I may have missed something completely obvious but the documentation is exactly helping, so I'm turning to you guys for help.

I'm trying to figure out just how many types of "deployment files" there are for Kubernetes. I call them "deployment files" because I really don't know what else to call them and they're usually associated with a deployment.

So far, every yml/yaml file I've seen start like this:

apiVersion:
kind: << this is what I'm asking about >>
metadata:

And so far I have seen this many "kind"(s)

ClusterConfig
ClusterRole
ClusterRoleBinding
CronJob
Deployment
Job
PersistentVolumeClaim
Pod
ReplicationController
Role
RoleBinding
Secret
Service
ServiceAccount

I'm sure there are many more. But I can't seem to find a location where they are listed and the contexts broken down.

So what I want to know is this,

  1. Where can I find an explanation for these yaml files?
  2. Where can I learn about the different kinds?
  3. Where can I get a broken down explanation of the minimum required fields/values are for any of these?
  4. Are there templates for these files?

Thanks

-- luis.madrigal
kubectl
kubernetes
kubernetes-pod

3 Answers

2/7/2020

When you are talking about specific yaml file containing the definition of specific kubernetes object, you can call them yaml manifests or simply yaml definition files. Using word Deployment for all of them isn't a good idea as there is already specific resource type defined and called by this name in kubernetes. So it's better you don't call them all deployments for consistency.

I'm sure there are many more. But I can't seem to find a location where they are listed and the contexts broken down.

Yes, there are a lot more of them and you can list those which are available by running:

kubectl api-resources

These different objects are actually called api-resources. As you can see they are listed in three columns: NAME, SHORTNAMES, APIGROUP, NAMESPACED and KIND

NAME                                       SHORTNAMES   APIGROUP                       NAMESPACED   KIND
bindings                                                                               true         Binding
componentstatuses                          cs                                          false        ComponentStatus
configmaps                                 cm                                          true         ConfigMap
endpoints                                  ep                                          true         Endpoints
events                                     ev                                          true         Event
limitranges                                limits                                      true         LimitRange
namespaces                                 ns                                          false        Namespace
nodes                                      no                                          false        Node

Note that the name of resource corresponds to its KIND but it is slightly different. NAME simply describes resource types as we are referring to them e.g. using kubectl command line utility. Just to give one example, when you want to list pods available in your cluster you simply type kubectl get pods. You don't have to use resource kind i.e. Pod in this context. You can but you don't have to. So kubectl get Pod or kubectl get ConfigMap will also return desired result. You can also refer to them by their shournames so kubectl get daemonsets and kubectl get ds are equivalent.

It's totally different when it comes to specific resource/object definition. In context of yaml definition file we must to use proper KIND of the resource. They are mostly start with capital letter and are written by co called CamelCase but there are exceptions from this rule.

I really recommend you to familiarize with kubernetes documentation. It is very user-friendly and nicely explains both key kubernetes concepts as well as all very tiny details.

Here you have even more useful commands for exploring API resources:

kubectl api-resources --namespaced=true      # All namespaced resources
kubectl api-resources --namespaced=false     # All non-namespaced resources
kubectl api-resources -o name                # All resources with simple output (just the resource name)
kubectl api-resources -o wide                # All resources with expanded (aka "wide") output
kubectl api-resources --verbs=list,get       # All resources that support the "list" and "get" request verbs
kubectl api-resources --api-group=extensions # All resources in the "extensions" API group

As @wargre already suggested in his comment, kubernetes official documentetion is definitely the best place to start as you will find there very detailed description of every resource.

-- mario
Source: StackOverflow

2/7/2020

This question will need a blog to answer but still in short you can try these options and command to learn from your kubectl CLI.

Learn to use kubectl explain command which shows you a list of Kubernetes objects:

$ kubectl explain

You can get detailed information about any of listed resources using this syntax

`$ kubectl explain pod

$ kubectl explain pod.spec

$ kubectl explain pod.spec.containers`

Or you can get yam template of the object by adding --recursive flag to explain command.

$ kubectl explain pod --recursive

This will also give you official document link.

So in short running kubectl explain with recursive option will list every thing.

-- DT.
Source: StackOverflow

2/7/2020

Understanding Kubernetes Objects

You may start from reading this article: Understanding Kubernetes Objects

Kubernetes Objects are persistent entities in the Kubernetes system. Kubernetes uses these entities to represent the state of your cluster. Specifically, they can describe:

  • What containerized applications are running (and on which nodes)
  • The resources available to those applications
  • The policies around how those applications behave, such as restart policies, upgrades, and fault-tolerance

A Kubernetes object is a “record of intent”–once you create the object, the Kubernetes system will constantly work to ensure that object exists. By creating an object, you’re effectively telling the Kubernetes system what you want your cluster’s workload to look like; this is your cluster’s desired state.

K8s API reference

A detailed description of all objects can be found in the Kubernetes API reference guide.

-- Yasen
Source: StackOverflow