• Keeping record of the change cause using the --record flag

  3 min read

  
  

  On Kubernetes, when we update objects such as a deployment or a daemonset we can check it's rollout history using kubectl rollout history:

  $ kubectl rollout history deploy pet2cattle
  deployment.apps/pet2cattle 
  REVISION  CHANGE-CAUSE
  21        <none>
  22        <none>
  23        <none>
  24        <none>
  26        <none>
  28        <none>
  29        <none>
  30        <none>
  32        <none>
  33        <none>
  34        <none>
  

  By default we won't be able to see a change cause, but we can fill this gap by setting the command that triggered the update adding the --record flag as follows:

  $ kubectl scale deployment/pet2cattle --replicas 2 --record
  deployment.apps/pet2cattle scaled
  

  18/05/2021

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• Rolling updates on Kubernetes deployments

  2 min read

  
  

  There are several strategies available for updating a deployment on Kubernetes, by default it will trigger a rolling update: It will deploy the new version before tearing down the old one so there's no downtime associated to it.

  Let's see how we can see this process by applying an update to a deployment:

  $ kubectl apply -f deployment.yaml
  

  17/05/2021

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• How to imperatively change a container's image

  2 min read

  
  

  To change a container's image we can:

  • Update the yaml definition and push it using kubectl apply
  • Use kubectl edit to update it using a definition fetched from the Kubernetes cluster itself
  • To use kubectl set image to set the new image

  Let's check how to use kubectl set image

  14/05/2021

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• Forward traffic to kubernetes services

  2 min read

  
  

  When we want to access services that run inside a kubernetes cluster that are not supposed to be normally accessed we can temporally run kubectl port-forward to forward traffic to our workstation. To be able to use it, the node must have socat installed.

  13/05/2021

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• Forcefully replace a terraform resource / terraform taint

  3 min read

  
  

  With terraform taint we are telling terraform that a particular object has become degraded so it will propose to replace it in the next plan. This command is going to be deprecated on terraform v1.0 since now we have the -replace flag on the apply command

  $ terraform taint kubernetes_namespace.pet2cattle_namespace
  Acquiring state lock. This may take a few moments...
  Resource instance kubernetes_namespace.pet2cattle_namespace has been marked as tainted.
  Releasing state lock. This may take a few moments...
  

  12/05/2021

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