Kubectl Usage Conventions

https://kubernetes.io/docs/reference/kubectl/conventions/

Using kubectl in Reusable Scripts

For a stable output in a script:

• Request one of the machine-oriented output forms, such as -o name, -o json, -o yaml, -o go-template, or -o jsonpath.
• Fully-qualify the version. For example, jobs.v1.batch/myjob. This will ensure that kubectl does not use its default version that can change over time.
• Don’t rely on context, preferences, or other implicit states.

Best Practices

kubectl run

For kubectl run to satisfy infrastructure as code:

• Tag the image with a version-specific tag and don’t move that tag to a new version. For example, use :v1234, v1.2.3, r03062016-1-4, rather than :latest (For more information, see Best Practices for Configuration).
• Check in the script for an image that is heavily parameterized.
• Switch to configuration files checked into source control for features that are needed, but not expressible via kubectl run flags.

You can use the --dry-run=client flag to preview the object that would be sent to your cluster, without really submitting it.Note: All kubectl generators are deprecated. See the Kubernetes v1.17 documentation for a list of generators and how they were used.

Generators

You can generate the following resources with a kubectl command, kubectl create --dry-run=client -o yaml:

  clusterrole         Create a ClusterRole.
  clusterrolebinding  Create a ClusterRoleBinding for a particular ClusterRole.
  configmap           Create a configmap from a local file, directory or literal value.
  cronjob             Create a cronjob with the specified name.
  deployment          Create a deployment with the specified name.
  job                 Create a job with the specified name.
  namespace           Create a namespace with the specified name.
  poddisruptionbudget Create a pod disruption budget with the specified name.
  priorityclass       Create a priorityclass with the specified name.
  quota               Create a quota with the specified name.
  role                Create a role with single rule.
  rolebinding         Create a RoleBinding for a particular Role or ClusterRole.
  secret              Create a secret using specified subcommand.
  service             Create a service using specified subcommand.
  serviceaccount      Create a service account with the specified name.

kubectl apply

• You can use kubectl apply to create or update resources. For more information about using kubectl apply to update resources, see Kubectl Book.

Q Node03 has our critical applications. We do not want to schedule any more apps on node03. Mark node03 as unschedulable but do not remove any apps currently running on it.

kubectl cordon node03