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Kubernetes

Kubernetes Commands: kubectl config – Tutorials and Examples

January 17, 2020 comments off

The kubectl command-line tool uses kubeconfig files(file named with – config) to find the information it needs to choose a cluster and communicate with the API server of a cluster.

Note:
A file that is used to configure access to clusters is called a kubeconfig file. This is a generic way of referring to configuration files. It does not mean that there is a file named kubeconfig.

How to set kubeconfig file to kubectl?

  • Method 1 – By default, kubectl looks for a file named config in the $HOME/.kube directory.
  • Method 2 – You can specify other kubeconfig files by setting the KUBECONFIG environment variable or
  • Method 3 – You can specify other kubeconfig files by setting the –kubeconfig flag.

The loading order follows these rules:

  • Rules 1 – If the –kubeconfig flag is set, then only that file is loaded. The flag may only be set once and no merging takes place.
  • Rules 2 – If $KUBECONFIG environment variable is set, then it is used as a list of paths (normal path delimiting rules for your system). These paths are merged. When a value is modified, it is modified in the file that defines the stanza. When a value is created, it is created in the first file that exists. If no files in the chain exist, then it creates the last file in the list.
  • Rules 3 – Otherwise, ${HOME}/.kube/config is used and no merging takes place.
$ kubectl help config

Available Commands:
  current-context Displays the current-context
  delete-cluster  Delete the specified cluster from the kubeconfig
  delete-context  Delete the specified context from the kubeconfig
  get-clusters    Display clusters defined in the kubeconfig
  get-contexts    Describe one or many contexts
  rename-context  Renames a context from the kubeconfig file.
  set             Sets an individual value in a kubeconfig file
  set-cluster     Sets a cluster entry in kubeconfig
  set-context     Sets a context entry in kubeconfig
  set-credentials Sets a user entry in kubeconfig
  unset           Unsets an individual value in a kubeconfig file
  use-context     Sets the current-context in a kubeconfig file
  view            Display merged kubeconfig settings or a specified kubeconfig file

Displays the kubectl config current-context command help.
$ kubectl config current-context --help

$ kubectl config view 

$ kubectl config get-contexts --help
# List all the contexts in your kubeconfig file
$ kubectl config get-contexts
# Describe one context in your kubeconfig file.
$ kubectl config get-contexts my-context

$ kubectl config get-clusters --help 
# List the clusters kubectl knows about
$ kubectl config get-clusters

$ kubectl config use-context --help      

# Use the context for the minikube cluster
$ kubectl config use-context minikube
     
$ kubectl config set-cluster --help

# Set only the server field on the e2e cluster entry without touching other values.
$ kubectl config set-cluster e2e --server=https://1.2.3.4

# Embed certificate authority data for the e2e cluster entry
$ kubectl config set-cluster e2e --certificate-authority=~/.kube/e2e/kubernetes.ca.crt

# Disable cert checking for the dev cluster entry
$ kubectl config set-cluster e2e --insecure-skip-tls-verify=true

$ kubectl config set-context --help

# Set the user field on the gce context entry without touching other values
kubectl config set-context gce --user=cluster-admin

$ kubectl config set-credentials --help

$ kubectl options
      --certificate-authority='': Path to a cert file for the certificate authority
      --client-certificate='': Path to a client certificate file for TLS
      --client-key='': Path to a client key file for TLS
      --cluster='': The name of the kubeconfig cluster to use
      --context='': The name of the kubeconfig context to use
      --insecure-skip-tls-verify=false: If true, the server's certificate will not be checked for
validity. This will make your HTTPS connections insecure
      --kubeconfig='': Path to the kubeconfig file to use for CLI requests.
      --token='': Bearer token for authentication to the API server
      --user='': The name of the kubeconfig user to use
      --username='': Username for basic authentication to the API server
      --password='': Password for basic authentication to the API server

Skeleton/Example of kube config file

Rajesh Kumar
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