update GPDB entrypoint file (#12)

* update entrypoint file
* update GPDB docs

docker_greenplum/README.md

@@ -1,20 +1,48 @@
-```bash
-docker build -t qpod0dev/greenplum --build-arg "BASE_NAMESPACE=qpod" .
+# GreenplumDB 
 
-docker run -it \
+This is the docker contianer for starting a GreenplumDB 7 cluster.
+https://docs.vmware.com/en/VMware-Greenplum/7/greenplum-database/landing-index.html
+
+Note: After the creation of a cluster, it is required to initialize the cluster using the functions in `$GPHOME/entrypoint.sh`.
+
+## Quick Start
+
+To start a GPDB single node cluster, try the command below, or refer to the `example/gpdb-single-node/docker-compose.yml`
+
+```bash
+docker run -d \
   -p 15432:5432  -p 10022:22 \
   -v /data/database/gpdb:/data/gpdb \
   -h gpdb-cdw \
   --name gpdb-cdw \
-  docker.io/qpod0dev/greenplum \
-  bash
+  docker.io/qpod0dev/greenplum
 
-docker run -d \
+# to change the password for gpadmin db user, enter the container and execute the command below.
+psql -d postgres -c "ALTER ROLE gpadmin WITH PASSWORD 'gpadmin';"
+```
+
+## Multi-node cluster on a single machine
+
+Please refer to the file `example/gpdb-single-vm/docker-compose.yml`.
+Note: it is neded to create folders `primary1` and `primary2` for segment nodes in `/data/database/greenplum`:
+```
+mkdir -pv /data/database/greenplum/primary1
+mkdir -pv /data/database/greenplum/primary2
+```
+
+# Debug
+
+```bash
+# to build the docker image
+docker build -t qpod0dev/greenplum --build-arg "BASE_NAMESPACE=qpod" .
+
+docker run -it \
   -p 15432:5432  -p 10022:22 \
   -v /data/database/gpdb:/data/gpdb \
   -h gpdb-cdw \
   --name gpdb-cdw \
-  docker.io/qpod0dev/greenplum
+  docker.io/qpod0dev/greenplum \
+  bash
 
 /bin/bash -c ${GPHOME}/entrypoint.sh
 ```

docker_greenplum/example/gpdb-single-vm/docker-compose.yml

@@ -23,6 +23,9 @@ services:
     volumes:
     - ./conf:/opt/gpdb/conf
     - /data/database/greenplum:/data/gpdb
+    depends_on:
+      - sdw1
+      - sdw2
 
   sdw1:
     image: "docker.io/qpod/greenplum"

docker_greenplum/rootfs/opt/gpdb/entrypoint.sh

@@ -28,3 +28,4 @@ else
   echo "Starting existing GPDB" && gpstart -a
 fi
 # tail -f gpAdminLogs/*.log
+bash