AMBARI-25751: Update README.md for dev-support/docker/centos7 (#3384)

dev-support/docker/centos7/README.md

@@ -11,12 +11,69 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 -->
+## Build and install Ambari by dev-support
+Dev support is used to quickly develop and test ambari, which runs on the docker containers.
 
-1、Build image ambari/develop:trunk-centos-7(build-image.sh)
-2、Build containers for cluster env(build-containers.sh)
-3、Clear containers after tests done(clear-containers.sh)
-4、Ambari UI、Ambari Server Debug Port、MariaDB Server are also exposed to local ports: 8080、5005、3306
-5、Docker host names are: ambari-server、ambari-agent-01、ambari-agent-02
-6、Extra configurations are in `build-containers.sh` last few lines, eg. Kerberos Configuration、Hive DB Configuration
-7、Re-build Ambari without re-creating clusters when code updates(build-ambari.sh)
-8、Distribute stack scripts without re-creating clusters(distribute-scripts.sh)
+### **Step 1**: Install build tools: Git、Docker
+The scripts require docker to be installed, since the compile process will run in a docker container and Ambari cluster also deploys on containers.
+
+**RHEL (CentOS 7) :**
+```shell
+yum install -y git docker
+```
+### **Step 2**: Download Ambari source
+```shell
+git clone https://github.com/apache/ambari.git
+```
+### **Step 3**: Enter workspace
+**RHEL (CentOS 7) :**
+```shell
+cd ambari/dev-support/docker/centos7/
+```
+### **Step 4**: Build develop basic image
+Run the setup command, you will get `ambari/develop:trunk-centos-7` image. It has the enviroment needed to compile Ambari and run servers such as Ambari Server, Ambari Agent, Mysql, etc.
+
+**RHEL (CentOS 7) :**
+```shell
+./build-image.sh
+```
+### **Step 5**: Build Ambari source & create Ambari cluster
+* The first compilation will take about 1 hour to download resources, and the next compilation will directly use the maven cache.
+* Ambari UI、Ambari Server Debug Port、MariaDB Server are also exposed to local ports: 8080、5005、3306.
+* Docker host names are: ambari-server、ambari-agent-01、ambari-agent-02.
+* Access admin page via http://localhost:8080 on your web browser. Log in with username `admin` and password `admin`.
+* Extra configurations are in `build-containers.sh` last few lines, eg. Kerberos Configuration、Hive DB Configuration.
+
+**RHEL (CentOS 7) :**
+```shell
+./build-containers.sh
+```
+### **Step 6**: Re-build Ambari Server
+Re-compile Ambari without re-create and deploy clusters.
+
+**RHEL (CentOS 7) :**
+```shell
+./build-ambari.sh
+```
+
+### **Step 7**: Redistribution stack
+Re-distribute stack scripts without re-create clusters.
+
+**RHEL (CentOS 7) :**
+```shell
+./distribute-scripts.sh
+```
+### **Step 8**: Clean Ambari cluster
+Clean up the containers of Ambari cluster when you are done developing or testing.
+
+**RHEL (CentOS 7) :**
+```shell
+./clear-containers.sh
+```
+### Step 9: Clean up the build environment
+**Note :** This operation will completely delete maven cache.
+
+**RHEL (CentOS 7) :**
+```shell
+docker rm -f ambari-rpm-build
+```