Create 8.faq.md (#901)

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+# FAQ
+
+This topic lists the frequently asked questions for using Nebula Dashboard. You can use the search box in the help center or the search function of the browser to match the questions you are looking for.
+
+## "What are Cluster, Node, and Service?"
+
+- Cluster: refers to a group of systems composed of nodes where multiple Nebula Graph services are located.
+
+- Node: refers to the physical or virtual machine hosting Nebula Graph services.
+
+- Service: refers to Nebula services, including Metad, Storaged, and Graphd services.
+
+## "What is the cluster status?"
+
+The status of a cluster is as follows:
+
+- installing: The cluster is being created. The process will take about 3 to 10 minutes.
+- healthy: All services in the cluster are healthy.
+- unhealthy: There is an unhealthy service in the cluster service.
+
+## "Why authorizing nodes?"
+
+Managing clusters requires the SSH information of the corresponding node. Therefore, you need to have at least an SSH account and the corresponding password with executable permissions before performing operations on Dashboard.
+
+## "What is scaling?"
+
+Nebula Graph is a distributed graph database that supports dynamic scaling services at runtime. Therefore, you can dynamically scale Storaged and Graphd services through Dashboard. The Metad service cannot be scaled.
+
+## "Why cannot operate on the Metad service?"
+
+The Metad service stores the metadata of the Nebula Graph database. Once the Metad service fails to function, the entire cluster may break down. Besides, the amount of data processed by the Metad service is not much, so it is not recommended to scale the Metad service. And we directly disabled operating on the Metad service in Dashboard to prevent the cluster from being unavailable due to the misoperation of users.
+
+## "What impact will the scaling have on the data?"
+
+- Scale out the Storaged service: Dashboard will create and start the Storaged service on the specified machine, which will not affect the existing data. You can choose to perform `Balance Data` on the `Service information` page or `Balance Leader` on the `Leader` page according to your own needs.
+
+- Scale in the Storaged service: Dashboard will automatically execute `Balance Data Remove` to ensure that the service is stopped after the data partition on the specified service is successfully migrated.
+
+- Scaling the Graphd service will not affect the data.
+
+## "Why Dashboard Enterprise Edition cannot be started?"
+
+- Make sure that the license file is copied to the Dashboard directory and `bash ./scripts/start.sh` is executed.
+
+- Make sure that the license is not expired.
+
+You can also execute `cat logs/webserver.log` in the Dashboard directory to view the startup information of each module. If the above conditions are met but Dashboard still cannot be started, go to [Nebula Graph Official Forum](https://discuss.nebula-graph.io/ "Click to go to Nebula Graph Official Forum") for consultation.
+
+## "Can I add the Nebula Graph installation package manually?"
+
+You can add the installation package manually in Dashboard. To download the system and RPM/DEB package you need, see [How to download Nebula Graph](https://nebula-graph.io/download/) and add the package to `dashboard/download/nebula-graph`. And you can select the added package for deployment when creating and scaling out a cluster.