Docs: add en/juicefs_on_k3s.md (#826)

* Docs: add en/juicefs_on_k3s.md

* Update

* Update
Co-authored-by: NChangjian Gao <gcj@juicedata.io>

docs/en/README.md

@@ -36,6 +36,7 @@ JuiceFS can simply and conveniently connect massive cloud storage directly to bi
   - [Use JuiceFS on Windows](juicefs_on_windows.md)
   - [Use JuiceFS on Docker](juicefs_on_docker.md)
   - [Use JuiceFS on Kubernetes](how_to_use_on_kubernetes.md)
+  - [Use JuiceFS on K3s](juicefs_on_k3s.md)
   - [Use JuiceFS on Hadoop](hadoop_java_sdk.md)
   - [JuiceFS enable S3 Gateway](s3_gateway.md)
   - [JuiceFS client compilation and upgrade](client_compile_and_upgrade.md)

docs/en/juicefs_on_k3s.md

+# Use JuiceFS on K3s
+
+[K3s](https://k3s.io/) is a functionally optimized lightweight Kubernetes distribution that is fully compatible with Kubernetes, that is, almost all operations on Kubernetes can be performed on K3s. K3s has packaged the entire container orchestration system into a binary program with a capacity of less than 100MB, which greatly reduces the environment dependency and installation of deploying Kubernetes production clusters. In contrast, K3s has lower performance requirements for the operating system, and ARM devices such as Raspberry Pi can be used to form a cluster.
+
+In this article, we will build a K3s cluster with two nodes, install and configure [JuiceFS CSI Driver](https://github.com/juicedata/juicefs-csi-driver) for the cluster, and finally create a Nginx Pod for verification.
+
+## Deploy a K3s cluster
+
+K3s has very low **minimum requirements** for hardware:
+
+- **Memory**：512MB+（recommend 1GB+）
+- **CPU**：1 core
+
+When deploying a production cluster, you can usually use the Raspberry Pi 4B (4 CPU cores, 8G memory) as the starting point for the hardware of a node. For details, see [Hardware Requirements](https://rancher.com/docs/k3s/latest/en/installation/installation-requirements/#hardware).
+
+### K3s server node
+
+The IP address of the server node is: `192.168.1.35`
+
+Use the script officially provided by K3s to deploy the server node on a regular Linux distribution.
+
+```shell
+$ curl -sfL https://get.k3s.io | sh -
+```
+
+After the deployment is successful, the K3s service will automatically start, and kubectl and other tools will also be installed.
+
+Execute the command to view the status of the node:
+
+```shell
+$ sudo kubectl get nodes
+NAME     STATUS   ROLES                  AGE   VERSION
+k3s-s1   Ready    control-plane,master   28h   v1.21.4+k3s1
+```
+
+Get the `node-token`：
+
+```shell
+$ sudo -u root cat /var/lib/rancher/k3s/server/node-token
+K1041f7c4fabcdefghijklmnopqrste2ec338b7300674f::server:3d0ab12800000000000000006328bbd80
+```
+
+### K3s worker node
+
+The IP address of the worker node is: `192.168.1.36`
+
+Execute the following command and change the value of `K3S_URL` to the IP or domain name of the server node, the default port is `6443`. Replace the value of `K3S_TOKEN` with the `node-token` obtained from the server node.
+
+```shell
+$ curl -sfL https://get.k3s.io | K3S_URL=http://192.168.1.35:6443 K3S_TOKEN=K1041f7c4fabcdefghijklmnopqrste2ec338b7300674f::server:3d0ab12800000000000000006328bbd80 sh -
+```
+
+After the deployment is successful, go back to the server node to check the node status:
+
+```shell
+$ sudo kubectl get nodes
+NAME     STATUS   ROLES                  AGE   VERSION
+k3s-s1   Ready    control-plane,master   28h   v1.21.4+k3s1
+k3s-n1   Ready    <none>                 28h   v1.21.4+k3s1
+```
+
+## Install CSI Driver
+
+It is consistent with the method of [Use JuiceFS on Kubernetes](how_to_use_on_kubernetes.md), you can install it through Helm or kubectl.
+
+Here we use kubectl, execute the following command to install the CSI Driver:
+
+```shell
+$ kubectl apply -f https://raw.githubusercontent.com/juicedata/juicefs-csi-driver/master/deploy/k8s.yaml
+```
+
+### Create Storage Class
+
+Copy and modify the following code to create a configuration file, for example: `juicefs-sc.yaml`
+
+```yaml
+apiVersion: v1
+kind: Secret
+metadata:
+  name: juicefs-sc-secret
+  namespace: kube-system
+type: Opaque
+stringData:
+  name: "test"
+  metaurl: "redis://juicefs.afyq4z.0001.use1.cache.amazonaws.com/3"
+  storage: "s3"
+  bucket: "https://juicefs-test.s3.us-east-1.amazonaws.com"
+  access-key: "<your-access-key-id>"
+  secret-key: "<your-access-key-secret>"
+---
+apiVersion: storage.k8s.io/v1
+kind: StorageClass
+metadata:
+  name: juicefs-sc
+provisioner: csi.juicefs.com
+reclaimPolicy: Retain
+volumeBindingMode: Immediate
+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
+```
+
+The `stringData` part of the configuration file is used to set the information related to the JuiceFS file system. It will create the file system based on the information you specify. When you need to use the pre-created file system in the storage class, you only need to fill in the `name` and `metaurl`, and the other items can be deleted or the value can be left blank.
+
+Execute the command to deploy the storage class:
+
+```shell
+$ kubectl apply -f juicefs-sc.yaml
+```
+
+View storage class status:
+
+```shell
+$ sudo kubectl get sc
+NAME                   PROVISIONER             RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
+local-path (default)   rancher.io/local-path   Delete          WaitForFirstConsumer   false                  28h
+juicefs-sc             csi.juicefs.com         Retain          Immediate              false                  28h
+```
+
+> **Note**: A storage class is associated with a JuiceFS file system. You can create as many storage classes as you need. But you need to pay attention to modifying the storage class name in the configuration file to avoid conflicts with the same name.
+
+## Use JuiceFS to persist Nginx data
+
+Next, deploy an Nginx Pod, using the persistent storage declared by the JuiceFS storage class.
+
+### Depolyment
+
+Create a configuration file, for example: `depolyment.yaml`
+
+```yaml
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: web-pvc
+spec:
+  accessModes:
+    - ReadWriteMany
+  resources:
+    requests:
+      storage: 10Pi
+  storageClassName: juicefs-sc
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx-run
+  labels:
+    app: nginx
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app: nginx
+  template:
+    metadata:
+      labels:
+        app: nginx
+    spec:
+      containers:
+        - name: nginx
+          image: linuxserver/nginx
+          ports:
+            - containerPort: 80
+          volumeMounts:
+            - mountPath: /config
+              name: web-data
+      volumes:
+        - name: web-data
+          persistentVolumeClaim:
+            claimName: web-pvc
+```
+
+Depoly it:
+
+```
+$ sudo kubectl apply -f depolyment.yaml
+```
+
+### Service
+
+Create a configuration file, for example: `service.yaml`
+
+```yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx-run-service
+spec:
+  selector:
+    app: nginx
+  ports:
+    - name: http
+      port: 80
+```
+
+Depoly it:
+
+```shell
+$ sudo kubectl apply -f service.yaml
+```
+
+### Ingress
+
+K3s is pre-installed with traefik-ingress by default. Create an ingress for Nginx through the following configuration. For example: `ingress.yaml`
+
+```yaml
+apiVersion: networking.k8s.io/v1
+kind: Ingress
+metadata:
+  name: nginx-run-ingress
+  annotations:
+    traefik.ingress.kubernetes.io/router.entrypoints: web
+spec:
+  rules:
+    - http:
+        paths:
+          - pathType: Prefix
+            path: "/web"
+            backend:
+              service:
+                name: nginx-run-service
+                port:
+                  number: 80
+```
+
+Depoly it:
+
+```shell
+$ sudo kubectl apply -f ingress.yaml
+```
+
+### Visit
+
+After the deployment is complete, use the host on the same LAN to access any cluster node, and you can see the Nginx welcome page.
+
+![](../images/k3s-nginx-welcome.png)
+
+Next, check whether the container has successfully mounted JuiceFS, and execute the command to check the pod status:
+
+```shell
+$ sudo kubectl get pods
+NAME                         READY   STATUS    RESTARTS   AGE
+nginx-run-7d6fb7d6df-qhr2m   1/1     Running   0          28h
+nginx-run-7d6fb7d6df-5hpv7   1/1     Running   0          24h
+```
+
+Execute the command to view the file system mount status of any pods:
+
+```shell
+$ sudo kubectl exec nginx-run-7d6fb7d6df-qhr2m -- df -Th
+Filesystem     Type          Size  Used Avail Use% Mounted on
+overlay        overlay        20G  3.2G   17G  17% /
+tmpfs          tmpfs          64M     0   64M   0% /dev
+tmpfs          tmpfs         2.0G     0  2.0G   0% /sys/fs/cgroup
+JuiceFS:jfs    fuse.juicefs  1.0P  174M  1.0P   1% /config
+/dev/sda1      ext4           20G  3.2G   17G  17% /etc/hosts
+shm            tmpfs          64M     0   64M   0% /dev/shm
+tmpfs          tmpfs         2.0G   12K  2.0G   1% /run/secrets/kubernetes.io/serviceaccount
+tmpfs          tmpfs         2.0G     0  2.0G   0% /proc/acpi
+tmpfs          tmpfs         2.0G     0  2.0G   0% /proc/scsi
+tmpfs          tmpfs         2.0G     0  2.0G   0% /sys/firmware
+```
+
+As you can see, the file system named `jfs` has been mounted to the `/config` directory of the container, and the used space is 174M.
+
+This indicates that the Pods in the cluster have been successfully configured and used JuiceFS to persist data.

docs/zh_cn/juicefs_on_k3s.md

-# K3s 使用 JuiceFS 持久化数据
+# K3s 使用 JuiceFS
 
-[K3s](https://k3s.io/) 是一个经过功能优化的 Kubernetes 发行版，它与 Kubernetes 完全兼容，即几乎所有在 Kubernetes 的操作都可以在 K3s 上执行。K3s 将整个容器编排系统打包进了一个容量不足 40MB 的二进制程序，减少了部署 Kubernetes 生产集群的环境依赖，大大降低了安装难度。相比之下，K3s 对操作系统的性能要求更低，树莓派等 ARM 设备都可以用来组建集群。
+[K3s](https://k3s.io/) 是一个经过功能优化的 Kubernetes 发行版，它与 Kubernetes 完全兼容，即几乎所有在 Kubernetes 的操作都可以在 K3s 上执行。K3s 将整个容器编排系统打包进了一个容量不足 100MB 的二进制程序，减少了部署 Kubernetes 生产集群的环境依赖，大大降低了安装难度。相比之下，K3s 对操作系统的性能要求更低，树莓派等 ARM 设备都可以用来组建集群。
 
 在本文中，我们会建立一个包含两个节点的 K3s 集群，为集群安装并配置使用 [JuiceFS CSI Driver](https://github.com/juicedata/juicefs-csi-driver)，最后会创建一个 Nginx 容器进行验证。