add how to use JuiceFS on Kubernetes doc (#184)

* add how to use on kubernetes doc

* add doc for installation with kubectl

README.md

@@ -92,7 +92,7 @@ There is a [command reference](docs/en/command_reference.md) to see all options
 
 ### Kubernetes
 
-There is a [Kubernetes CSI driver](https://github.com/juicedata/juicefs-csi-driver) to use JuiceFS in Kubernetes easily.
+[Using JuiceFS on Kubernetes](docs/en/how_to_use_on_kubernetes.md) is so easy, have a try.
 
 ### Hadoop Java SDK
 

docs/en/how_to_use_on_kubernetes.md

+# Use JuiceFS on Kubernetes
+
+JuiceFS provides the [CSI driver](https://github.com/juicedata/juicefs-csi-driver) for Kubernetes.
+
+
+
+## Prerequisites
+
+- Kubernetes 1.14+
+
+
+
+## Installation
+
+### Install with helm 
+
+To install helm, refer to the [Helm install guide](https://github.com/helm/helm#install) , helm 3 is required.
+
+1. Prepare a file `values.yaml` with access infomation about redis and object storage (take amazon s3 `us-east-1` as an example)
+
+```yaml
+storageClasses:
+- name: juicefs-sc
+  enabled: true
+  reclaimPolicy: Delete
+  backend:
+    name: "test"
+    metaurl: "redis://juicefs.afyq4z.0001.use1.cache.amazonaws.com/3"
+    storage: "s3"
+    accessKey: ""
+    secretKey: ""
+    bucket: "https://juicefs-test.s3.us-east-1.amazonaws.com"
+```
+
+  Here we assign AWS [IAM role](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_switch-role-ec2.html) for the EC2 Kuberentes node, otherwise the `accessKey` and `secretKey` cannot be empty. We use ElasticCache redis as the meta store.
+
+2. Install
+
+```shell
+helm repo add juicefs-csi-driver https://juicedata.github.io/juicefs-csi-driver/
+helm repo update
+helm upgrade juicefs-csi-driver juicefs-csi-driver/juicefs-csi-driver --install -f ./values.yaml
+```
+
+3. Check the deployment
+
+- Check running pods: the deployment will launch a `StatefulSet` with replica `1` for the `juicefs-csi-controller` and a `DaemonSet` for `juicefs-csi-node` ，so run `kubectl -n kube-system get pods | grep juicefs-csi` should see `n+1` （where `n` is the number of worker node of the kubernetes cluster) pods is running
+- Check secret: `kubectl -n kube-system describe secret juicefs-sc-secret` will show the secret with above `backend` fields: 
+
+```
+Name:         juicefs-sc-secret
+Namespace:    kube-system
+Labels:       app.kubernetes.io/instance=juicefs-csi-driver
+              app.kubernetes.io/managed-by=Helm
+              app.kubernetes.io/name=juicefs-csi-driver
+              app.kubernetes.io/version=0.7.0
+              helm.sh/chart=juicefs-csi-driver-0.1.0
+Annotations:  meta.helm.sh/release-name: juicefs-csi-driver
+              meta.helm.sh/release-namespace: default
+
+Type:  Opaque
+
+Data
+====
+access-key:  0 bytes
+bucket:      47 bytes
+metaurl:     54 bytes
+name:        4 bytes
+secret-key:  0 bytes
+storage:     2 bytes
+```
+
+
+- Check storage class: `kubectl get sc` will show the storage class like this:
+
+```
+NAME                 PROVISIONER                RECLAIMPOLICY   VOLUMEBINDINGMODE   ALLOWVOLUMEEXPANSION   AGE
+juicefs-sc           csi.juicefs.com            Delete          Immediate           false                  21m
+```
+
+
+### Install with kubectl
+
+1. Deploy the driver:
+
+```bash
+kubectl apply -f https://raw.githubusercontent.com/juicedata/juicefs-csi-driver/master/deploy/k8s.yaml
+```
+
+Here we use the `juicedata/juicefs-csi-driver:latest` image, if we want to use the specified tag such as `v0.7.0` , we should download the deploy YAML file and modified it:
+
+```bash
+curl -sSL https://raw.githubusercontent.com/juicedata/juicefs-csi-driver/master/deploy/k8s.yaml | sed 's@juicedata/juicefs-csi-driver@juicedata/juicefs-csi-driver:v0.7.0@' | kubectl apply -f -
+```
+
+2. Create storage class
+
+- Add secret `juicefs-sc-secret` :
+
+```bash
+kubectl -n kube-system create secret generic juicefs-sc-secret \
+  --from-literal=name=test \
+  --from-literal=meta-url=redis://juicefs.afyq4z.0001.use1.cache.amazonaws.com/3 \
+  --from-literal=storage=s3 \
+  --from-literal=bucket=https://juicefs-test.s3.us-east-1.amazonaws.com \
+  --from-literal=access-key="" \
+  --from-literal=secret-key=""
+
+```
+
+- Create storage class use `kubectl apply`:
+
+```yaml
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: juicefs-sc
+provisioner: csi.juicefs.com
+parameters:
+  csi.storage.k8s.io/node-publish-secret-name: juicefs-sc-secret
+  csi.storage.k8s.io/node-publish-secret-namespace: kube-system
+  csi.storage.k8s.io/provisioner-secret-name: juicefs-sc-secret
+  csi.storage.k8s.io/provisioner-secret-namespace: kube-system
+reclaimPolicy: Delete
+volumeBindingMode: Immediate
+```
+
+
+# Use JuiceFS
+
+Now we can use JuiceFS in our pods.  Here we create a `PVC` and refer it in a pod as an example:
+
+```yaml
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: jtext-pvc
+spec:
+  accessModes:
+  - ReadWriteMany
+  resources:
+    requests:
+      storage: 10Gi
+  storageClassName: juicefs-sc
+---
+apiVersion: v1
+kind: Pod
+metadata:
+  name: juicefs-app
+spec:
+  containers:
+  - args:
+    - -c
+    - while true; do echo $(date -u) >> /data/out.txt; sleep 5; done
+    command:
+    - /bin/sh
+    image: busybox
+    name: app
+    volumeMounts:
+    - mountPath: /data
+      name: juicefs-pv
+  volumes:
+  - name: juicefs-pv
+    persistentVolumeClaim:
+      claimName: jtext-pvc
+
+```
+
+Save above content to a file named like `juicefs-app.yaml` ，then use command `kubectl apply -f juicefs-app.yaml` to bootstrap the pod.
+
+
+
+For more details about using JuiceFS on Kubernetes please refer [JuiceFS CSI driver](https://github.com/juicedata/juicefs-csi-driver).