KodeCloud CKAD Misc

Links: 111 KodeCloud Index

Doing dry runs

k apply -f dep.yaml --dry-run=client This will not create the resource, instead, tell you whether the resource can be created and if your command is right.

  • Output the yaml files of imperative commands

    • k run nginx --image=nginx --dry-run=client -o yaml
    • Other imperative commands are create (creating a service, creating a deployment, etc), expose etc.

  • Get the yaml file for any resource:

    • k get <resource-type> <resource-name> -o yaml > definition.yaml
    • This is useful when you have already defined resources in a cluster and you don't have their yaml files.

  • Formatting the output:

    1. -o json: Output a JSON formatted API object.
    2. -o name: Print only the resource name and nothing else.
    3. -o wide: Output in the plain-text format with any additional information.
    4. -o yaml: Output a YAML formatted API object.

  • Forcefully apply a file

    • k apply -f --force <file-name>.yaml

  • Get objects from all the namespaces:

    • k get <resource-name> -A
    • Example: k get pods -A
    • Get all the objects in all namespaces: k get all -A

  • Service full DNS: <svc-name>.<namespace>.svc.cluster.local

  • We can remove the headers from the output of any command using:
    • k <command> --no-headers
If we want to get the short names or api version or kind or find out whether they are namespaced or not we can use k api-resources

Long form: k api-resource -o wide

What happens when you do k get pods
  • The request goes to the kubeapi-server.
  • When the request hits the kubeapi-server it goes through an authentication process and this is done using certificates.
  • If the request was sent using kubectl then we know that the kubeconfig file has the required certificates configured.
  • After authentication the request goes through and authorisation process. This is achieved using RBAC.
  • If the user is allowed to list the pods then he will be able to list the pods. attachments/Pasted image 20221008204838.jpg

  • If the scheduler can't schedule the pod then it will go into PENDING state.

  • Get all the events in a namespace: k get events

  • Describing the api-server pod for important details
    • k get pods -n kube-system
    • k describe pod/kube-apiserver-controlplane -n kube-system - It may be named differently depending on how it is setup.

Last updated: 2023-05-10