Consider this post more of a summary or a cheat sheet of the important parts mentioned in the documentation about DNS records automatically created for Services and Pods in your K8S cluster’s DNS Server. Kubelet configures each Pod’s DNS (/etc/resolv.conf) so that the running containers can make requests to/perform DNS lookups for Services and other […]

If you’re running a StatefulSet application/workload in Kubernetes like a database (Postgres, Mongo, ElasticSearch, etc.), at some point your disk storage will get full and you will have to increase the size of the StatefulSet’s persistent volumes. Let’s go through the steps to do this. First of all, if you are provisioning persistent volumes for […]

Let’s cover everything you need to know about resizing Kubernetes volumes to expand their size (upsizing). Downsizing is not possible. We will talk keeping persistent volumes in mind but most of what we discuss should also be applicable to Generic ephemeral volumes. Also when we say “resizing volumes”, we refer to resizing the actual storage […]

In Kubernetes, if you store some data (create a file, write to it, modify a file, etc.) in a container running inside your pod, the changes won’t persist once the container stops running (crashes, stops normally or restarts). For better data persistence, Kubernetes provides the following options: Now when specifically working with Persistent Volumes, they […]

The short answer is IT DEPENDS. Let’s say you have a PVC called myclaim: You can go ahead and create multiple pods whose spec try to use this PVC, K8S will allow us to schedule all these pods without any validation error: But whether multiple pods are able to mount the same volume that the […]

The short answer is NO. As mentioned in the documentation, PersistentVolumeClaims (PVC) and PersistentVolumes (PV) in K8S have a one-to-one relationship: A PVC to PV binding is a one-to-one mapping, using a ClaimRef which is a bi-directional binding between the PersistentVolume and the PersistentVolumeClaim. When a PVC is using a PV, its spec.volumeName points to […]

Sometimes we want to cleanup a bunch of pods that are failing to get scheduled or failing to execute after getting scheduled. Removal and cleanup of pods failing to execute can even help scale down your cluster workers and hence reduce costs. When I say failing pods, it means pods with statuses (that you see […]

The short answer to this question is that you cannot. For a slightly descriptive answer, keep reading. Let’s say you try deleting a PersistentVolume (kubectl delete pv [pv_name]) that is bound to a PersistentVolumeClaim, it will get stuck in Terminating state. This is because the PV has a Finalizer (kubernetes.io/pv-protection) that prevents it from accidentally […]

A PersistentVolume with persistentVolumeReclaimPolicy: Retain (not applicable for Delete) used by a PersistentVolumeClaim transitions from Bound to Released state when the attached PVC is deleted. If you try to create a new PVC and bind that to the same PV, the PVC will continue to be in Pending state and the PV in Released state. […]

You can run kubectl describe pvc [pvc_name] and look at the Used By label to find out the list of pods using that particular PersistentVolumeClaim in your Kubernetes/K8S cluster’s namespace. The myclaim pvc above is being used by pod-1 and pod-2 in the test namespace. Sometimes it might be useful to go through all the […]