01 - Core Concepts - ReplicaSets

ReplicaSets

$ kubectl get replicaset       

$ kubectl get rs                  

Get the current ReplicaSets deployed.

$ kubectl describe rs <replicaset-name>          

Get detailed information about ReplicaSet.

$ kubectl delete pod <pod-name1> <pod-name2> <pod-name3>    

$ kubectl delete rs <replicaset-name>                                          

$ kubectl delete -f <file-name>.yaml                                            

Delete pods/ReplicaSet.

Q: Why are there still 4 PODs, even after you deleted one?

A: ReplicaSet ensures that desired number of PODs always run

Fix YAML file

$ kubectl create -f replicaset-definition-1.yaml        

➥ 先用此指令，得到 Error Msg

$ kubectl api-resources | grep replicaset                  

Print the supported API resources.

$ kubectl explain replicaset                                    

Get the documentation of the resource and its fields.

$ vim replicaset-definition-1.yaml                           

$ kubectl create -f replicaset-definition-1.yaml        

Create a resource from a file or from stdin.

$ kubectl apply -f replicaset-definition-1.yaml         

Apply a configuration to a resource by file name or stdin. 

• The resource name must be specified. This resource will be created if it doesn't exist yet. 
• To use 'apply', always create the resource initially with either 'apply' or 'create --save-config'.

Fix the original ReplicaSet

$ kubectl edit rs <replicaset-name>                            

※ 若更改了 image，還需要將原始的 pod 刪除，才會套用新的 image。

```yaml

spec:

  template:

    spec:

      containers:

        image: busybox

```

※ 若更改了 replicas，無需將原始的 pod 刪除，會自動套用新的 replicas 設定。

```yaml

spec:

  replicas: 5

```

$ kubectl scale rs <replicaset-name> --replicas=5           

※ 若更改了 replicas，無需將原始的 pod 刪除，會自動套用新的 replicas 設定。