I have a kubernetes deployment which generates hundreds of thousands of files. I've mounted and EFS instance into my pod with a persistent volume and persistent volume claim. I've tried running my deployment but ran into an issue and now I need to wipe the persistent volume. What's the best way to do this?
I've tried running exec-ing into my pod and running rm -rf but that didn't seem to make any progress after 30 minutes. I also tried using rsync but that also was incredibly slow.
Does EFS offer a mechanism to delete files from the console or command line? Does k8s offer a mechanism to wipe a persistent volume (claim)? What's the best way to give my pod a fresh slate to start working with again?
EDIT: I tried deleting and recreating the PVC but that didn't seem to work since my pod crashlooped once the deployment was restarted with the new PVC.
EDIT 2: I was mounting my PVC with a subPath - changing the subPath gave my pod a fresh new directory to work with. This was a nice workaround but I still would like to delete the old data in the EFS volume so I don't have to pay for it.
I am pretty new to Kubernetes so I don't have much idea. Last day a pod went down and I was thinking if I would be able to recover the tmp folder.
So basically I want to know that when a pod in Kubernetes goes down, does it lose access to the "/tmp" folder ?
Unless you configure otherwise, this folder will be considered storage within the container, and the contents will be lost when the container terminates.
Similarly to how you can run a container in docker, write something to the filesystem within the container, then stop and remove the container, start a new one, and find the file you wrote within the container is no longer there.
If you want to keep the /tmp folder contents between restarts, you'll need to attach a persistent volume to it and mount it as /tmp within the container, but with the caveat that if you do that, you cannot use that same volume with other replicas in a deployment unless you use a read-write-many capable filesystem underneath, like NFS.
I have used some bitnami charts in my kubernetes app. In my pod, there is a file whose path is /etc/settings/test.html. I want to override the file. When I search it, I figured out that I should mount my file by creating a configmap. But how can I use the created configmap with the existed pod . Many of the examples creates a new pod and uses the created config map. But I dont want to create a new pod, I wnat to use the existed pod.
Thanks
If not all then almost all pod specs are immutable, meaning that you can't change them without destroying the old pod and creating a new one with desired parameters. There is no way to edit pod volume list without recreating it.
The reason behind this is that pods aren't meant to be immortal. Pods meant to be temporary units that can be spawned/destroyed according to scheduler needs. In general, you need a workload object that does pod management for you (a Deployement, StatefulSet, Job, or DaemonSet, depenging on deployment strategy and application nature).
There are two ways to edit a file in an existing pod: either by using kubectl exec and console commands to edit the file in place, or kubectl cp to copy an already edited file into the pod. I advise you against both of these, because this is not permanent. Better backup the necessary data, switch deployment type to Deployment with one replica, then go with mounting a configMap as you read on the Internet.
When changing a variable in a configmap, the environment variables inside running pods are not updated.
We have a stateful pod that cannot be restarted easily.
Trying to update the environment variable inside the container with
export VARIABLE_TO_BE_UPDATED="new value"
lasts a little while but is then rolled back automatically after some short time (maybe this has something to due with the open session).
Any way to update those environment variables (manually) in a persistent way without restarting the pod?
You can't reload a ConfigMap that was already mounted. The ConfigMap is read from the API and dumped into a volume before the container is started, it remains static afterwards.
Another way to do this could be to use a sidecard container, watching over changes to those ConfigMaps, refreshing copies in some volume that would be shared with your application container, then instructing your application to reload its configuration. A common implementation for this would be the Prometheus Rule Reloader.
I'm running a MySQL deployment on Kubernetes however seems like my allocated space was not enough, initially I added a persistent volume of 50GB and now I'd like to expand that to 100GB.
I already saw the a persistent volume claim is immutable after creation, but can I somehow just resize the persistent volume and then recreate my claim?
Yes, as of 1.11, persistent volumes can be resized on certain cloud providers. To increase volume size:
Edit the PVC (kubectl edit pvc $your_pvc) to specify the new size. The key to edit is spec.resources.requests.storage:
Terminate the pod using the volume.
Once the pod using the volume is terminated, the filesystem is expanded and the size of the PV is increased. See the above link for details.
It is possible in Kubernetes 1.9 (alpha in 1.8) for some volume types: gcePersistentDisk, awsElasticBlockStore, Cinder, glusterfs, rbd
It requires enabling the PersistentVolumeClaimResize admission plug-in and storage classes whose allowVolumeExpansion field is set to true.
See official docs at https://kubernetes.io/docs/concepts/storage/persistent-volumes/#expanding-persistent-volumes-claims
Update: volume expansion is available as a beta feature starting Kubernetes v1.11 for in-tree volume plugins. It is also available as a beta feature for volumes backed by CSI drivers as of Kubernetes v1.16.
If the volume plugin or CSI driver for your volume support volume expansion, you can resize a volume via the Kubernetes API:
Ensure volume expansion is enabled for the StorageClass (allowVolumeExpansion: true is set on the StorageClass) associated with your PVC.
Request a change in volume capacity by editing your PVC (spec.resources.requests).
For more information, see:
https://kubernetes.io/docs/concepts/storage/persistent-volumes/#expanding-persistent-volumes-claims
https://kubernetes-csi.github.io/docs/volume-expansion.html
No, Kubernetes does not support automatic volume resizing yet.
Disk resizing is an entirely manual process at the moment.
Assuming that you created a Kubernetes PV object with a given capacity and the PV is bound to a PVC, and then attached/mounted to a node for use by a pod. If you increase the volume size, pods would continue to be able to use the disk without issue, however they would not have access to the additional space.
To enable the additional space on the volume, you must manually resize the partitions. You can do that by following the instructions here. You'd have to delete the pods referencing the volume first, wait for it to detach, than manually attach/mount the volume to some VM instance you have access to, and run through the required steps to resize it.
Opened issue #35941 to track the feature request.
There is some support for this in 1.8 and above, for some volume types, including gcePersistentDisk and awsBlockStore, if certain experimental features are enabled on the cluster.
For other volume types, it must be done manually for now. In addition, support for doing this automatically while pods are online (nice!) is coming in a future version (currently slated for 1.11):
For now, these are the steps I followed to do this manually with an AzureDisk volume type (for managed disks) which currently does not support persistent disk resize (but support is coming for this too):
Ensure PVs have reclaim policy "Retain" set.
Delete the stateful set and related pods. Kubernetes should release the PVs, even though the PV and PVC statuses will remain Bound. Take special care for stateful sets that are managed by an operator, such as Prometheus -- the operator may need to be disabled temporarily. It may also be possible to use Scale to do one pod at a time. This may take a few minutes, be patient.
Resize the underlying storage for the PV(s) using the Azure API or portal.
Mount the underlying storage on a VM (such as the Kubernetes master) by adding them as a "Disk" in the VM settings. In the VM, use e2fsck and resize2fs to resize the filesystem on the PV (assuming an ext3/4 FS). Unmount the disks.
Save the JSON/YAML configuration of the associated PVC.
Delete the associated PVC. The PV should change to status Released.
Edit the YAML config of the PV, after which the PV status should be Available:
specify the new volume size in spec.capacity.storage,
remove the spec.claimref uid and resourceVersion fields, and
remove status.phase.
Edit the saved PVC configuration:
remove the metadata.resourceVersion field,
remove the metadata pv.kubernetes.io/bind-completed and pv.kubernetes.io/bound-by-controller annotations, and
change the spec.resources.requests.storage field to the updated PV size, and
remove all fields inside status.
Create a new resource using the edited PVC configuration. The PVC should start in Pending state, but both the PV and PVC should transition relatively quickly to Bound.
Recreate the StatefulSet and/or change the stateful set configuration to restart pods.
In terms of PVC/PV 'resizing', that's still not supported in k8s, though I believe it could potentially arrive in 1.9
It's possible to achieve the same end result by dealing with PVC/PV and (e.g.) GCE PD though..
For example, I had a gitlab deployment, with a PVC and a dynamically provisioned PV via a StorageClass resource. Here are the steps I ran through:
Take a snapshot of the PD (provided you care about the data)
Ensure the ReclaimPolicy of the PV is "Retain", patch if necessary as detailed here: https://kubernetes.io/docs/tasks/administer-cluster/change-pv-reclaim-policy/
kubectl describe pv <name-of-pv> (useful when creating the PV manifest later)
Delete the deployment/pod (probably not essential, but seems cleaner)
Delete PVC and PV
Ensure PD is recognised as being not in use by anything (e.g. google console, compute/disks page)
Resize PD with cloud provider (with GCE, for example, this can actually be done at an earlier stage, even if the disk is in use)
Create k8s PersistentVolume manifest (this had previously been done dynamically via the use of the StorageClass resource). In the PersistentVolume yaml spec, I had "gcePersistentDisk: pdName: <name-of-pd>" defined, along with other details that I'd grabbed at step 3. make sure you update the spec.capacity.storage to the new capacity you want the PV to have (although not essential, and has no effect here, you may want to update the storage capacity/value in your PVC manifest, for posterity)
kubectl apply (or equivalent) to recreate your deployment/pod, PVC and PV
note: some steps may not be essential, such as deleting some of the existing deployment/pod.. resources, though I personally prefer to remove them, seeing as I know the ReclaimPolicy is Retain, and I have a snapshot.
The first thing you can do is, check for the storage class that you are using, see if allowVolumeExpansion is set to `true. If yes then simply update PVC with requested volume and check for status in PVCs.
If this doesn't work for you then try this (for AWS users).
Check for the attached volume id in the PV (under awsElasticBlockStore -> `volume).
Go to Volumes in AWS, and modify volume to whatever is required
SSH into the node to which is volume is currently attached (to find node name describe pod and check for node key)
use lsblk to list the volume attached
Run resize2fs or xfs_growfs based on what type of volume you have.
exec into the pod run df -h and check the volume.
Note: You can only modify a volume once in 6 hours.
Edit the PVC (kubectl edit pvc $your_pvc) to specify the new size. The key to edit is spec.resources.requests.storage:
Even though this answer worked quite well for one pvc of my statefulset, the others didn't managed to resize. I guess it's because the pods restarted too quick, leaving no time for the resizing process to start due to the backoff. In fact, the pods started fast but took some time to be considered as ready (increasing backoff).
Here's my workaround:
Update the pvc
Backup the sts spec
k get sts <sts-name> -o yaml > sts.yaml
Then delete the sts with cascade=orphan. Thus, the pods will still run
kubectl delete sts --cascade=orphan <sts-name>
Then delete one of the pod whose pvc wouldn't resize
kubectl delete pod <pod-name>
Wait for the pvc to resize
kubectl get pvc -w
Reapply the sts so the pod comes back
kubectl apply -f sts.yaml
Wait for the pod to come back
Repeat until all pvc are resized!
Below is how we can expand the volume size of azure disks mounted on statefulset(STS) pod when storage class is used.(AWS EBS and GCP Persistent volumes should be similar).
Summary:
Delete the statefulset.
Update the volume size on the PVC. Wait till the condition message prompts to start up the pods.
Apply new statefulset with updated volume size and you should see the volume getting resized when the pod starts up.
Complete Steps:
Check if volume resize is enabled in the storage class.
kubectl get storageclass
First, delete the statefulset. This is required because
The volumes should be unmounted and detached from the node before it can be resized.
The volume size on the STS YAML is immutable (cant be updated).
We will have to create a new STS with higher volume size later on. Don't forget to backup the STS YAML if you don't have it in your repo's.
After deleting the STS, wait for some time so that k8s can detach the volume from the node.
Next, modify the PVC with higher value for volume size.
At this point, if the volume is still attached, you will see below warning message in the PVC events.
Either the volume is still mounted to the pod or you just have to wait and give some time to k8s.
Next, run the describe command on the PVC, you should now see a message(in conditions) prompting you to start up the pod.
kubectl describe pvc app-master-volume-app-master-0
In the earlier step, we had deleted the statefulset. Now we need to create and apply a new STS with higher volume size. This should match the value earlier modified in the PVC spec.
When the new pod gets created, you will see pod event like shown below which indicates that the volume resize is successful.
Yes, it can be, after version 1.8, have a look at volume expansion here
Volume expansion was introduced in v1.8 as an Alpha feature
I have persistent volume with self created StorageClass (allowVolumeExpansion: true).
PV spec: accessMode: readWriteOnce
PVC spec: same
When I upgrade PV, changes are not reflected in PVC.