Update influxdb documentation with database initialization

influxdb/content.md

@@ -131,3 +131,72 @@ $ docker run --rm --link=influxdb -it influxdb influx -host influxdb
 ```
 
 At the moment, you cannot use `docker exec` to run the influx client since `docker exec` will not properly allocate a TTY. This is due to a current bug in Docker that is detailed in [docker/docker#8755](https://github.com/docker/docker/issues/8755).
+
+### Database Initialization
+
+The InfluxDB image contains some extra functionality for initializing a database. These options are not suggested for production, but are quite useful when running standalone instances for testing.
+
+The database initialization script will only be called when running `influxd`. It will not be executed when running any other program.
+
+#### Environment Variables
+
+The InfluxDB image uses several environment variables to automatically configure certain parts of the server. They may significantly aid you in using this image.
+
+##### INFLUXDB_DB
+
+Automatically initializes a database with the name of this environment variable.
+
+##### INFLUXDB_HTTP_AUTH_ENABLED
+
+Enables authentication. Either this must be set or `auth-enabled = true` must be set within the configuration file for any authentication related options below to work.
+
+##### INFLUXDB_ADMIN_USER
+
+The name of the admin user to be created. If this is unset, no admin user is created.
+
+##### INFLUXDB_ADMIN_PASSWORD
+
+The password for the admin user configured with `INFLUXDB_ADMIN_USER`. If this is unset, a random password is generated and printed to standard out.
+
+##### INFLUXDB_USER
+
+The name of a user to be created with no privileges. If `INFLUXDB_DB` is set, this user will be granted read and write permissions for that database.
+
+##### INFLUXDB_USER_PASSWORD
+
+The password for the user configured with `INFLUXDB_USER`. If this is unset, a random password is generated and printed to standard out.
+
+##### INFLUXDB_READ_USER
+
+The name of a user to be created with read privileges on `INFLUXDB_DB`. If `INFLUXDB_DB` is not set, this user will have no granted permissions.
+
+##### INFLUXDB_READ_USER_PASSWORD
+
+The password for the user configured with `INFLUXDB_READ_USER`. If this is unset, a random password is generated and printed to standard out.
+
+##### INFLUXDB_WRITE_USER
+
+The name of a user to be created with write privileges on `INFLUXDB_DB`. If `INFLUXDB_DB` is not set, this user will have no granted permissions.
+
+##### INFLUXDB_WRITE_USER_PASSWORD
+
+The password for the user configured with `INFLUXDB_WRITE_USER`. If this is unset, a random password is generated and printed to standard out.
+
+#### Initialization Files
+
+If the Docker image finds any files with the extensions `.sh` or `.iql` inside of the `/docker-entrypoint-initdb.d` folder, it will execute them. The order they are executed in is determined by the shell. This is usually alphabetical order.
+
+#### Manually Initializing the Database
+
+To manually initialize the database and exit, the `/init-influxdb.sh` script can be used directly. It takes the same parameters as the `influxd run` command. As an example:
+
+```console
+$ docker run --rm \
+      -e INFLUXDB_DB=db0 -e INFLUXDB_ADMIN_ENABLED=true
+      -e INFLUXDB_ADMIN_USER=admin -e INFLUXDB_ADMIN_USER=supersecretpassword
+      -e INFLUXDB_USER=telegraf -e INFLUXDB_USER_PASSWORD=secretpassword
+      -v $PWD:/var/lib/influxdb \
+      /init-influxdb.sh
+```
+
+The above would create the database `db0`, create an admin user with the password `supersecretpassword`, then create the `telegraf` user with your telegraf's secret password. It would then exit and leave behind any files it created in the volume that you mounted.