update emqx content (#2452)

* update emqx content

* emqx: address review comments

emqx/content.md

@@ -32,51 +32,35 @@ 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.
 
-By default, the environment variables with `EMQX_` prefix are mapped to key-value pairs in configuration files.
-
-You can change the prefix by overriding `HOCON_ENV_OVERRIDE_PREFIX`.
-
 Example:
 
-```bash
-EMQX_LISTENERS__SSL__DEFAULT__ACCEPTORS <--> listeners.ssl.default.acceptors
-EMQX_ZONES__DEFAULT__MQTT__MAX_PACKET_SIZE <--> zones.default.mqtt.max_packet_size
-```
+	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
+-	All upper case letters are replaced with lower case letters
 -	`__` is replaced with `.`
 
-If `HOCON_ENV_OVERRIDE_PREFIX=DEV_` is set:
-
-```bash
-DEV_LISTENER__SSL__EXTERNAL__ACCEPTORS <--> listener.ssl.external.acceptors
-DEV_MQTT__MAX_PACKET_SIZE              <--> mqtt.max_packet_size
-DEV_LISTENERS__TCP__DEFAULT__BIND      <--> listeners.tcp.default.bind
-```
-
 For example, set MQTT TCP port to 1883
 
 ```console
-$ docker run -d --name emqx -e DEV_LISTENERS__TCP__DEFAULT__BIND=1883 -p 18083:18083 -p 1883:1883 %%IMAGE%%:latest
+$ docker run -d --name emqx -e EMQX_DASHBOARD__DEFAULT_PASSWORD=mysecret -p 18083:18083 -p 1883:1883 %%IMAGE%%:latest
 ```
 
-Please read more about EMQX configuration in the [official documentation](https://www.emqx.io/docs/en/v5.0/admin/cfg.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
 
-| Options     | Default        | Mapped | Description                |
-|-------------|----------------|--------|----------------------------|
-| `EMQX_NAME` | container name | none   | EMQX node short name       |
-| `EMQX_HOST` | container IP   | none   | EMQX node host, IP or FQDN |
+Environment variable `EMQX_NODE__NAME` allows you to specify an EMQX node name, which defaults to `<container_name>@<container_ip>`.
 
-These environment variables are used during container startup phase only in [docker-entrypoint.sh](./docker-entrypoint.sh).
-
-If `EMQX_NAME` and `EMQX_HOST` are set, and `EMQX_NODE_NAME` is not set, `EMQX_NODE_NAME=$EMQX_NAME@$EMQX_HOST`. Otherwise `EMQX_NODE_NAME` is taken verbatim.
+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.
 
@@ -89,8 +73,7 @@ Let's create a static node list cluster from docker-compose.
     emqx1:
       image: %%IMAGE%%:latest
       environment:
-      - "EMQX_NAME=emqx"
-      - "EMQX_HOST=node1.emqx.io"
+      - "[email protected]"
       - "EMQX_CLUSTER__DISCOVERY_STRATEGY=static"
       - "EMQX_CLUSTER__STATIC__SEEDS=[[email protected], [email protected]]"
       networks:
@@ -101,8 +84,7 @@ Let's create a static node list cluster from docker-compose.
     emqx2:
       image: %%IMAGE%%:latest
       environment:
-      - "EMQX_NAME=emqx"
-      - "EMQX_HOST=node2.emqx.io"
+      - "[email protected]"
       - "EMQX_CLUSTER__DISCOVERY_STRATEGY=static"
       - "EMQX_CLUSTER__STATIC__SEEDS=[[email protected], [email protected]]"
       networks:
@@ -124,7 +106,7 @@ Let's create a static node list cluster from docker-compose.
 -	View cluster
 
 ```bash
-  $ docker exec -it my_emqx_emqx1_1 sh -c "emqx_ctl cluster status"
+  $ docker exec -it my_emqx_emqx1_1 sh -c "emqx ctl cluster status"
   Cluster status: #{running_nodes => ['[email protected]','[email protected]'],
                     stopped_nodes => []}
 ```
@@ -134,10 +116,9 @@ Let's create a static node list cluster from docker-compose.
 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`
 
-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:
 
@@ -145,8 +126,6 @@ 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
 
@@ -155,19 +134,15 @@ services:
     image: %%IMAGE%%:latest
     restart: always
     environment:
-      EMQX_NAME: foo_emqx
-      EMQX_HOST: 127.0.0.1
+      EMQX_NODE__NAME: [email protected]
     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).