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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.yaml17/05/2021
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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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How to add entries to a pod's /etc/hosts file
2 min read
The /etc/hosts file is a Kubernetes-managed file so we cannot add entries freely to it. If we want to add entries to it we will have to use the hostAliases field in the Pod's spec.
$ kubectl exec -it demo-pod -- cat /etc/hosts # Kubernetes-managed hosts file. 127.0.0.1 localhost ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet fe00::0 ip6-mcastprefix fe00::1 ip6-allnodes fe00::2 ip6-allrouters 10.103.198.74 demo-pod11/05/2021
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AWS EKS: How to resize Persistent Volumes
3 min read
On a AWS EKS cluster, at the time of this writing, by default you cannot resize volumes provisioned with the default gp2 StorageClass. This is because on the default StorageClass the allowVolumeExpansion is set to false, preventing the volume expansion:
$ kubectl get sc NAME PROVISIONER RECLAIMPOLICY VOLUMEBINDINGMODE ALLOWVOLUMEEXPANSION AGE gp2 (default) kubernetes.io/aws-ebs Delete WaitForFirstConsumer false 78d10/05/2021
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terraform state list: List resources from the terraform state
1 min read
To be able to get a list of resources managed by terraform we can use terraform state list for listing all the resources on the terraform state:
07/05/2021
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formatting Terraform code
2 min read
One of the nicest functions terraform has is terraform fmt: Just as go fmt would do with Go code, it will rewrite Terraform configuration files (.tf and .tfvars files) to a canonical format and style. This will improve it's readability, helping making the code more consistent.
06/05/2021
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Kubernetes: Image pull policies
2 min read
On Kubernetes we can configure using the Pod manifest under which conditions we want to query the container registry to pull images by using the imagePullPolicy setting. We can configure the it on several objects like Deployment, StatefulSet, Pod, Job... In fact, we can set it on any object that includes a Pod template
apiVersion: v1 kind: Pod metadata: name: test-pod namespace: demo spec: containers: - image: alpine imagePullPolicy: IfNotPresent (...)05/05/2021
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terraform: Import existing resources for terraform to manage them
3 min read
If we have some of the infrastructure that were created manually we can still import it into the terraform state. This ensures you can have a smooth transition from manually created resources to Infrastructure as Code
To do so we will be using then terraform import command:
$ terraform import The import command expects two arguments. Usage: terraform import [options] ADDR ID (...)04/05/2021
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