Merge pull request #1676 from desmap/patch-1

Update README.md

Author: yosifkit

postgres/content.md

@@ -63,6 +63,8 @@ Note 2: This variable defines the superuser password in the PostgreSQL instance,
 
 This optional environment variable is used in conjunction with `POSTGRES_PASSWORD` to set a user and its password. This variable will create the specified user with superuser power and a database with the same name. If it is not specified, then the default user of `postgres` will be used.
 
+Be aware that if this parameter is specified, PostgreSQL will still show `The files belonging to this database system will be owned by user "postgres"` during initialization. This refers to the Linux system user (from `/etc/passwd` in the image) that the `postgres` daemon runs as, and as such is unrelated to the `POSTGRES_USER` option. See the section titled "Arbitrary `--user` Notes" for more details.
+
 ### `POSTGRES_DB`
 
 This optional environment variable can be used to define a different name for the default database that is created when the image is first started. If it is not specified, then the value of `POSTGRES_USER` will be used.