ReStructuredText Demo

k8s-volumes

#NFS Volumes create NFS share on my QNAP with squash option no_root_squash.

#Local volumes Didnt manage to launch

Change nodes ip sudo vim /var/lib/kubelet/kubeadm-flags.env --node-ip=192.168.50.12 KUBELET_KUBEADM_ARGS="--cgroup-driver=cgroupfs --network-plugin=cni --pod-infra-container-image=k8s.gcr.io/pause:3.2 --resolv-conf=/run/systemd/resolve/resolv.conf --node-ip=192.168.50.12"

systemctl restart kubelet

#exec

kubectl exec --stdin --tty mysql-deployment-bfcd64b55-mqp4q -- /bin/bash

#sharing vol between pods My working solutuion not advised:

apiVersion: v1 kind: PersistentVolume metadata:

name: task-pv-volume labels:

System Message: ERROR/3 (<string>, line 30)

Unexpected indentation.

type: local

spec:

storageClassName: manual capacity:

System Message: ERROR/3 (<string>, line 34)

Unexpected indentation.

storage: 1Gi

System Message: WARNING/2 (<string>, line 35)

Block quote ends without a blank line; unexpected unindent.

accessModes:

• ReadWriteOnce

hostPath:

path: "/mnt/data"

apiVersion: v1 kind: PersistentVolumeClaim metadata:

name: task-pv-claim

spec:

storageClassName: manual accessModes:

System Message: ERROR/3 (<string>, line 46)

Unexpected indentation.

• ReadWriteOnce

System Message: WARNING/2 (<string>, line 47)

Block quote ends without a blank line; unexpected unindent.

resources:

requests:

storage: 1Gi

apiVersion: apps/v1 kind: Deployment metadata:

name: mysql-deployment labels:

System Message: ERROR/3 (<string>, line 56)

Unexpected indentation.

app: mysql

spec:

replicas: 1 selector:

System Message: ERROR/3 (<string>, line 60)

Unexpected indentation.

matchLabels:

app: mysql

System Message: WARNING/2 (<string>, line 62)

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template:

metadata:

labels:

app: mysql

spec:

containers:

• name: mysql image: mysql:5.7 ports:

  System Message: ERROR/3 (<string>, line 71)

  Unexpected indentation.

  • containerPort: 3306

  System Message: WARNING/2 (<string>, line 72)

  Block quote ends without a blank line; unexpected unindent.

  volumeMounts:

  • mountPath: "/var/lib/mysql" subPath: "mysql" name: mysql-data

  env:

  • name: MYSQL_ROOT_PASSWORD valueFrom:

    System Message: ERROR/3 (<string>, line 79)

    Unexpected indentation.

    secretKeyRef:

    name: mysql-secrets key: ROOT_PASSWORD

volumes:

• name: mysql-data persistentVolumeClaim:

  System Message: ERROR/3 (<string>, line 85)

  Unexpected indentation.

  claimName: task-pv-claim

#sharing dir between pods

First of all. Kubernetes doesn't have integrated functionality to share storage between hosts. There are several options below. But first how to share storage if you already have some volumes set up.

To share a volume between multiple pods you'd need to create a PVC with access mode ReadWriteMany

kind: PersistentVolumeClaim apiVersion: v1 metadata:

name: my-pvc

spec:

accessModes:

• ReadWriteMany

System Message: WARNING/2 (<string>, line 103)

Definition list ends without a blank line; unexpected unindent.

storageClassName: myvolume resources:

System Message: ERROR/3 (<string>, line 105)

Unexpected indentation.

requests:

storage: 1Gi

After that you can mount it to multiple pods:

apiVersion: v1 kind: Pod metadata:

name: myapp1

spec:

containers:

...

volumeMounts:

• mountPath: /data name: data subPath: app1

System Message: WARNING/2 (<string>, line 120)

Block quote ends without a blank line; unexpected unindent.

volumes:

• name: data persistentVolumeClaim:

  System Message: ERROR/3 (<string>, line 123)

  Unexpected indentation.

  claimName: 'my-pvc'

--- apiVersion: v1 kind: Pod metadata:

name: myapp2

spec:

containers:

...

volumeMounts:

• mountPath: /data name: data subPath: app2

System Message: WARNING/2 (<string>, line 136)

Block quote ends without a blank line; unexpected unindent.

volumes:

• name: data persistentVolumeClaim:

  System Message: ERROR/3 (<string>, line 139)

  Unexpected indentation.

  claimName: 'my-pvc'

Of course, persistent volume must be accessible via network. Otherwise you'd need to make sure that all the pods are scheduled to the node with that volume.

There are several volume types that are suitable for that and not tied to any cloud provider:

NFS RBD (Ceph Block Device) CephFS Glusterfs Portworx Volumes Of course, to use a volume you need to have it first. That is, if you want to consume NFS you need to setup NFS on all nodes in K8s cluster. If you want to consume Ceph, you need to setup Ceph cluster and so on.

The only volume type that supports Kubernetes out of the box is Portworks. There are instruction on how to set it up in GKE.

To setup Ceph cluster in K8s there's a project in development called Rook.

But this is all overkill if you just want a folder from one node to be available in another node. In this case just setup NFS server. It wouldn't be harder than provisioning other volume types and will consume much less cpu/memory/disk resources. ## Example1 Configure a Pod to Use a PersistentVolume for Storage

https://kubernetes.io/blog/2018/04/13/local-persistent-volumes-beta/

apiVersion: v1 kind: PersistentVolume metadata:

name: mysql-pv-volume labels:

System Message: ERROR/3 (<string>, line 165)

Unexpected indentation.

type: local

spec:

capacity:

storage: 1Gi

accessModes:

• ReadWriteOnce

System Message: WARNING/2 (<string>, line 171)

Definition list ends without a blank line; unexpected unindent.

persistentVolumeReclaimPolicy: Retain storageClassName: local-storage local:

System Message: ERROR/3 (<string>, line 174)

Unexpected indentation.

path: /mnt/data

System Message: WARNING/2 (<string>, line 175)

Block quote ends without a blank line; unexpected unindent.

nodeAffinity:

required:

nodeSelectorTerms: - matchExpressions:

System Message: ERROR/3 (<string>, line 179)

Unexpected indentation.

• key: kubernetes.io/hostname operator: In values: - node

apiVersion: v1 kind: PersistentVolumeClaim metadata:

name: mysql-pv-claim

spec:

storageClassName: local-storage accessModes:

System Message: ERROR/3 (<string>, line 191)

Unexpected indentation.

• ReadWriteOnce

System Message: WARNING/2 (<string>, line 192)

Block quote ends without a blank line; unexpected unindent.

resources:

requests:

storage: 1Gi