Is there any way to access Google cloud Kubernetes persistent volume data without using pod. I cannot start pod due to data corruption in persistent volume. Have any command line tool or any other way.
If you have any concerns running pod with any specific application, in that case, you can run the Ubuntu POD and attach that pod to the PVC and access the data.
There also another option to clone the PV and PVC, perform the testing, and newly created PV and PVC while the old one will work as the backup option.
For cloning PV and PVC you can also use the tool : https://velero.io/
You can also attach the PVC to the POD in read-only mode and try accessing the data.
PersistentVolume resources are cluster resources that exist independently of Pods. This means that the disk and data represented by a PersistentVolume continue to exist as the cluster changes and as Pods are deleted and recreated.
It is possible to save data from your PersistentVolume with Status: Terminating and RetainPolicy set to default(delete). Your PersistentVolumes will not be terminated until there is a pod, deployment or to be more specific a PersistentVolumeClaim using it.
The steps we took to remedy our broken state are as follows:
The first thing you want to do is to create a snapshot of your PersistentVolumes.
In GKE console, go to Compute Engine -> Disks and find your volume there and create a snapshot of your volume. use
kubectl get pv | grep pvc-name
Use the snapshot to create a disk:
gcloud compute disks create name-of-disk --size=10 --source-snapshot=name-of-snapshot --type=pd-standard --zone=your-zone
At this point, stop the services using the volume and delete the volume and volume claim.
Re-create the volume manually with the data from the disk and update your volume claim to target a specific volume file.
For more information refer to the links below.
Accessing file shares from Google Kubernetes Engine clusters.
Configure a Pod to Use a PersistentVolume for Storage
Related
In a Kubernetes cluster on Oracle cloud, I have a pod with an Apache server.
This pod needs a persistent volume so I used a persistentVolumeClaim and the cloud provider is able to automatically create an associated volume (Oracle Block Volume).
The access mode used by the PVC is readWriteOnce and therefore the volume created has the same access mode.
Everything work great.
Now I want to backup this volume using borg backup and borgmatic by starting a new pod regularly with a cronJob.
This backup pod needs to mount the volume in read only.
Question:
Can I use the previously defined PVC?
Do I need to create a new PVC with readOnly access mode?
As per documentation:
ReadWriteOnce:
the volume can be mounted as read-write by a single node. ReadWriteOnce access mode still can allow multiple pods to access the volume when the pods are running on the same node.
That means if you make a strict rule for deploying your pods to the same node, you can use the same PVC, here's the INSTRUCTION
I'm learning Kubernetes and there is something I don't get well.
There are 3 ways of setting up static storage:
Pods with volumes you attach diretctly the storage to
Pods with a PVC attached to its volume
StatefulSets with also PVC inside
I can understand the power of PVC when working together with StorageClass, but not when working with static storage and local storage like hostPath
To me, it sounds very similar:
In the first case I have a volume directly attached to a pod.
In the second case I have a volume statically attached to a PVC, which is also manually attached to a Pod. In the end, the volume will be statically attached to the Pod.
On both cases, the data will remain when the Pod is terminates and will be adopted by the next Pod which the corresponing definition, right?
The only profit I see from using PVCs over plain Pod is that you can define the acces mode. Apart of that. Is there a difference when working with hostpath?
On the other hand, the advantage of using a StatefulSet instead of a PVC is (if understood properly) that it get a headless service, and that the rollout and rollback mechanism works differently. Is that the point?
Thank you in advance!
Extracted from this blog:
The biggest difference is that the Kubernetes scheduler understands
which node a Local Persistent Volume belongs to. With HostPath
volumes, a pod referencing a HostPath volume may be moved by the
scheduler to a different node resulting in data loss. But with Local
Persistent Volumes, the Kubernetes scheduler ensures that a pod using
a Local Persistent Volume is always scheduled to the same node.
Using hostPath does not garantee that a pod will restart on the same node. So you pod can attach /tmp/storage on k8s-node-1, then if you delete and re-create the pod, it may attach tmp/storage on k8s-node-[2-n]
On the contrary, if you use PVC/PV with local persistent storage class, then if you delete and re-create a pod, it will stick on the node which handle the local persistent storage.
StatefulSet creates pods and has volumeClaimTemplate field, which creates a dedicated PVC for each pod. So each pod created by the statefulSet will have its own dedicated storage, linked with Pod->PVC->PV->Storage. So StatefulSet use also the PVC/PV mechanism.
More details are available here.
I have a StatefulSet-1 running with 3 replicas & each pod writing logs to its own persistent volume say pv1,pv2,pv3 (achieved using volumeClaimTemplates:)
I have another StatefulSet-2 running with 3 replicas & I want each POD of StatefulSet-2 access already created StatefulSet-1's volumes i.e. pv1,pv2 & pv3 for processing seperate logs written by each pod of StatefulSet-1.
So pv1,pv2,pv3 should be using by both StatefulSet1 & StatefulSet2 since pv1,pv2,pv3 created as part of StatefulSet-1 deployment! pv1,pv2,pv3 will ofcourse takes POD's name of StatefulSet-1 which is ok for StatefulSet-2.
How to configure StatefulSet2 to achieve the above scenario? please help!
Thanks & Regards,
Sudhir
This won't work.
1. PVs backed by GCE disks are in readWriteOnce mode so 1 pvc per pod.
2. You are achieving the statefulset pods with PVCs using PVC templates which rely on dynamic volume provisioning to create the appropriate PVs and PVCs.
If you need these pods to share the PVC, your best bet is to use a readWriteMany PV such as one backed by NFS. You will also need to create the pods of statefulSet-2 manually to have them mount the appropriate PVCs. You could achieve this by creating a single pod deployment for each one.
Something else to consider, can you have the containers of each statefulSet run together in the same pods? Normally this is not recommended, but it would allow them both to share the same volumes (as long as they are not using the same ports)
I want a kubernetes data to be backed up. So I have a persistent disk with kubernetes cluster and have set reclaimPolicy: Retain on storage.yaml file to make sure disks should not be deleted.
After the deletion of kubernetes cluster the disk retains on compute Engine -> Disks. But with the help of disk i am unable to create a kubernetes cluster. I have options only to create VM in GCP.
Is there a possible way to create a new kubernetes cluster with the existing disk on GCP
To use your existing Persistent Disk in a new GKE cluster, you'll need to first create the new cluster, then:
create and apply new PersistentVolume and PersistentVolumeClaim objects based on the name of your existing PD.
Once those exist in your cluster, you'll be able to give a Pod's container access to that volume by specifying values for the container's volumeMounts.mountPath and volumeMounts.name in the pod definition file.
You'll find more details about how to achieve this in the doc here.
I am using rookio on Kubernetes with CoreOS for dynamically creating Persistent Volume.
So I create a PersistentVolumeClaim (kubectl create -f postgres-pvc.yaml) and apply a patch for persistentVolumeReclaimPolicy to Retain. I do a "kubectl get pv"and I can see a dynamically created persistentvolume and is bound. Now when I delete the PersitentVolumeClaim the status goes to Released.
I have stored some precious data in that persistentvolume. Is there a way I can reuse that persistentvolume that has gone into Released status?
thanks
-sonam
If you have precious data that you want to use in another PostgreSQL pod, maybe StatefulSets is which you are looking for, as it allows:
Stable, persistent storage [...] across Pod (re)schedulings.
Therefore, I would advise you to deploy your PostgreSQL database as a StatefulSet. You would need to check that your already existing Volume is bound.
[1] https://kubernetes.io/docs/concepts/workloads/controllers/statefulset/