docs(docker): sync README.md with the official image docs

deploy/docker/README.md

@@ -50,20 +50,17 @@ The EMQX broker runs as Linux user `emqx` in the docker container.
 
 All EMQX Configuration in [`etc/emqx.conf`](https://github.com/emqx/emqx/blob/master/apps/emqx/etc/emqx.conf) can be configured via environment variables.
 
-The environment variables with `EMQX_` prefix are mapped to key-value pairs in configuration files.
-
 Example:
 
-```bash
-EMQX_DASHBOARD__DEFAULT_PASSWORD       <--> dashboard.default_password
-EMQX_NODE__COOKIE                      <--> node.cookie
-EMQX_LISTENERS__SSL__default__ENABLE   <--> listeners.ssl.default.enable
-```
+	EMQX_DASHBOARD__DEFAULT_PASSWORD       <--> dashboard.default_password
+	EMQX_NODE__COOKIE                      <--> node.cookie
+	EMQX_LISTENERS__SSL__default__ENABLE   <--> listeners.ssl.default.enable
+
 Note: The lowercase use of 'default' is not a typo. It is used to demonstrate that lowercase environment variables are equivalent.
 
-+ Prefix `EMQX_` is removed
-+ All upper case letters is replaced with lower case letters
-+ `__` is replaced with `.`
+-	Prefix `EMQX_` is removed
+-	All upper case letters are replaced with lower case letters
+-	`__` is replaced with `.`
 
 For example, set MQTT TCP port to 1883
 
@@ -71,38 +68,30 @@ For example, set MQTT TCP port to 1883
 $ docker run -d --name emqx -e EMQX_DASHBOARD__DEFAULT_PASSWORD=mysecret -p 18083:18083 -p 1883:1883 emqx/emqx:latest
 ```
 
-Please read more about EMQX configuration in the [official documentation](https://www.emqx.io/docs/en/v5.0/configuration/configuration.html)
+Please read more about EMQX configuration in the [official documentation](https://docs.emqx.com/en/emqx/latest/configuration/configuration.html)
 
 #### EMQX node name configuration
 
-A node name consists of two parts, `EMQX_NAME` part and `EMQX_HOST` part connected by a the symbol `@`. For example: `emqx@127.0.0.1`.
-
-Environment variables `EMQX_NODE_NAME` or `EMQX_NODE__NAME` can be used to set a EMQX node name.
-If neither of them is set, EMQX will resolve its node name from the running environment or other environment varialbes used for node discovery.
-
-When running in docker, by default, `EMQX_NAME` and `EMQX_HOST` are resolved as below:
+Environment variable `EMQX_NODE__NAME` allows you to specify an EMQX node name, which defaults to `<container_name>@<container_ip>`.
 
-| Options      | Default         | Description                  |
-| -------------| --------------- | -----------------------------|
-| `EMQX_NAME`  | container name  | EMQX node short name         |
-| `EMQX_HOST`  | container IP    | EMQX node host, IP or FQDN   |
+If not specified, EMQX determines its node name based on the running environment or other environment variables used for node discovery.
 
 ### Cluster
 
-EMQX supports a variety of clustering methods, see our [documentation](https://www.emqx.io/docs/en/latest/deploy/cluster/intro.html) for details.
+EMQX supports a variety of clustering methods, see our [documentation](https://docs.emqx.com/en/emqx/latest/deploy/cluster/create-cluster.html) for details.
 
 Let's create a static node list cluster from docker-compose.
 
-+ Create `docker-compose.yaml`:
+-	Create `docker-compose.yaml`:
 
-  ```yaml
+```yaml
   version: '3'
 
   services:
     emqx1:
       image: emqx/emqx:latest
       environment:
-      - "EMQX_NODE_NAME=emqx@node1.emqx.io"
+      - "EMQX_NODE__NAME=emqx@node1.emqx.io"
       - "EMQX_CLUSTER__DISCOVERY_STRATEGY=static"
       - "EMQX_CLUSTER__STATIC__SEEDS=[emqx@node1.emqx.io, emqx@node2.emqx.io]"
       networks:
@@ -113,7 +102,7 @@ Let's create a static node list cluster from docker-compose.
     emqx2:
       image: emqx/emqx:latest
       environment:
-      - "EMQX_NODE_NAME=emqx@node2.emqx.io"
+      - "EMQX_NODE__NAME=emqx@node2.emqx.io"
       - "EMQX_CLUSTER__DISCOVERY_STRATEGY=static"
       - "EMQX_CLUSTER__STATIC__SEEDS=[emqx@node1.emqx.io, emqx@node2.emqx.io]"
       networks:
@@ -124,31 +113,30 @@ Let's create a static node list cluster from docker-compose.
   networks:
     emqx-bridge:
       driver: bridge
-  ```
+```
 
-+ Start the docker-compose cluster
+-	Start the docker-compose cluster
 
-  ```bash
+```bash
   docker-compose -p my_emqx up -d
-  ```
+```
 
-+ View cluster
+-	View cluster
 
-  ```bash
-  $ docker exec -it my_emqx_emqx1_1 sh -c "emqx_ctl cluster status"
+```bash
+  $ docker exec -it my_emqx_emqx1_1 sh -c "emqx ctl cluster status"
   Cluster status: #{running_nodes => ['emqx@node1.emqx.io','emqx@node2.emqx.io'],
                     stopped_nodes => []}
-  ```
+```
 
 ### Persistence
 
 If you want to persist the EMQX docker container, you need to keep the following directories:
 
-+ `/opt/emqx/data`
-+ `/opt/emqx/etc`
-+ `/opt/emqx/log`
+-	`/opt/emqx/data`
+-	`/opt/emqx/log`
 
-Since data in these folders are partially stored under the `/opt/emqx/data/mnesia/${node_name}`, the user also needs to reuse the same node name to see the previous state. In detail, one needs to specify the two environment variables: `EMQX_NAME` and `EMQX_HOST`, `EMQX_HOST` set as `127.0.0.1` or network alias would be useful.
+Since data in these folders are partially stored under the `/opt/emqx/data/mnesia/${node_name}`, the user also needs to reuse the same node name to see the previous state. To make this work, one needs to set the host part of `EMQX_NODE__NAME` to something static that does not change when you restart or recreate the container. It could be container name, hostname or loopback IP address `127.0.0.1` if you only have one node.
 
 In if you use docker-compose, the configuration would look something like this:
 
@@ -156,8 +144,6 @@ In if you use docker-compose, the configuration would look something like this:
 volumes:
   vol-emqx-data:
     name: foo-emqx-data
-  vol-emqx-etc:
-    name: foo-emqx-etc
   vol-emqx-log:
     name: foo-emqx-log
 
@@ -166,18 +152,15 @@ services:
     image: emqx/emqx:latest
     restart: always
     environment:
-      EMQX_NODE_NAME: foo_emqx@127.0.0.1
+      EMQX_NODE__NAME: foo_emqx@127.0.0.1
     volumes:
       - vol-emqx-data:/opt/emqx/data
-      - vol-emqx-etc:/opt/emqx/etc
       - vol-emqx-log:/opt/emqx/log
 ```
 
-Note that `/opt/emqx/etc` contains some essential configuration files. If you want to mount a host directory in the container to persist configuration overrides, you will need to bootstrap it with [default configuration files](https://github.com/emqx/emqx/tree/master/apps/emqx/etc).
-
 ### Kernel Tuning
 
-Under Linux host machine, the easiest way is [Tuning guide](https://www.emqx.io/docs/en/latest/deploy/tune.html).
+Under Linux host machine, the easiest way is [Tuning guide](https://docs.emqx.com/en/emqx/latest/performance/tune.html).
 
 If you want tune Linux kernel by docker, you must ensure your docker is latest version (>=1.12).