Merge pull request #1087 from GeoCat/master

Updated documentation of how-to connect to a postgres database

geonetwork/variant-postgres.md

@@ -8,28 +8,30 @@ In order to setup the connection from geonetwork, you **must** inject the follow
 
 If your postgres instance is listening on a non-standard port, you must also set that variable: - `POSTGRES_DB_PORT`: postgres port on your database server (defaults to `5432`)
 
-### Linking to a postgres container
+### Connecting to a postgres database
 
-Linking to a postgres container, is pretty straightforward: - `--link <some-postgres-container>:postgres`
+If you want to connect to a postgres server, you need to pass an extra environment variable, `POSTGRES_DB_HOST`, containing the address of this server.
 
-For instance, if you want to run the official image for postgres, you could launch it like this:
+If you want to connect to an **external database server**, you can use either the IP address or the DNS as `POSTGRES_DB_HOST`. For instance, if the server is running on `mydns.net`, on port `5434`, the username is `postgres` and the password is `mysecretpassword`:
 
 ```console
-$ docker run --name some-postgres -p 5432:5432 -d postgres
+$ docker run --name geonetwork -d -p 8080:8080 -e POSTGRES_DB_HOST=mydns.net -e POSTGRES_DB_PORT=5434 -e POSTGRES_DB_USERNAME=postgres -e POSTGRES_DB_PASSWORD=mysecretpassword geonetwork:postgres
 ```
 
-And then you could launch geonetwork, linking to this container, and setting the required environment variables:
+If are want to **run postgres on a container**, you can use the container name as `POSTGRES_DB_HOST`: just make sure that containers can discover each other, by **running them in the same user-defined network**. For instance, you can create a bridge network:
 
 ```console
-$ docker run --name geonetwork -d -p 8080:8080 --link some-postgres:postgres -e POSTGRES_DB_USERNAME=postgres -e POSTGRES_DB_PASSWORD=mysecretpassword geonetwork:postgres
+$ docker network create --driver bridge mynet
 ```
 
-### Connecting to a postgres instance
+Then if you want to run the official image of postgres, using `some-postgres` as container name, you could launch it like this:
 
-If you want to connect to a postgres server running somewhere, you need to pass an extra environment variable, containing the IP address for this server (which could be localhost, if you are running it locally). - `POSTGRES_DB_HOST`: IP address of your database server
+```console
+$ docker run --name some-postgres --network=mynet -d postgres
+```
 
-For instance, if the server is running on `192.168.1.10`, on port `5434`, the username is `postgres` and the password is `mysecretpassword`:
+And then you could launch geonetwork, making sure you join the same network, and setting the required environment variables, including the `POSTGRES_DB_HOST`:
 
 ```console
-$ docker run --name geonetwork -d -p 8080:8080 -e POSTGRES_DB_HOST=192.168.1.10 -e POSTGRES_DB_PORT=5434 -e POSTGRES_DB_USERNAME=postgres -e POSTGRES_DB_PASSWORD=mysecretpassword geonetwork:postgres
+$ docker run --name geonetwork -d -p 8080:8080 --network=mynet -e POSTGRES_DB_HOST=some-postgres -e POSTGRES_DB_PORT=5432 -e POSTGRES_DB_USERNAME=postgres -e POSTGRES_DB_PASSWORD=mysecretpassword geonetwork:postgres
 ```