#4324 - Allow configuring UID GID etc in Kubernetes

- Improve documentation

inception/inception-doc/src/main/resources/META-INF/asciidoc/admin-guide/installation_docker.adoc

@@ -101,6 +101,33 @@ annotations and knowledge bases, these are stored in files on disk). For product
 recommended to use a dedicated database server (i.e. MariaDB or compatible) instead of the embedded
 SQL database.
 
+== Memory and other Java options
+
+By default, {application-name} will use 80% of the memory allocated to the container.
+However, if you allocate very little or very much memory to the container, you may want to adjust this.
+
+For example, to set the available memory (RAM) to e.g. 4GB, append `-Xmx4g`.
+
+[source,shell,subs="+attributes"]
+----
+$ docker run -it -e JAVA_OPTS=-Xmx4g ghcr.io/inception-project/inception:{revnumber}
+----
+
+Be sure to leave some memory for the operating system inside the Docker container as well. Instead of setting a fixed value for the memory, you might consider allocating a percentage of the container's memory to {application-name} using `-XX:MaxRAMPercentage=80`.
+
+[source,shell,subs="+attributes"]
+----
+$ docker run -it -e JAVA_OPTS=-XX:MaxRAMPercentage=80 ghcr.io/inception-project/inception:{revnumber}
+----
+
+The applications logs the amount of memory it will use during startup. Check this value to validate that your memory setting takes effect.
+
+----
+INFO [main] [SYSTEM] boot - Max. application memory: 4096MB
+---
+
+You also pass additional options to the Java runtime through the `JAVA_OPTS` environment variable. This also includes system properties, e.g. `-DpropertName=value`. Most of the settings that can be configured in the `settings.properties` file can also be supplied in this way instead.
+
 == Customizing UID/GID
 
 By default, {product-name} runs with the UID 2000 and the GID 2000. On startup, any files belonging to {product-name} are automatically reassigned to these UID/GID, in the Docker container itself as well as in any volume potentially mounted under `/export` within the container. If you need the application to run as a different UID/GID, you can override these values when starting the container using the `APP_UID` and `APP_GID` environment variables.
@@ -109,6 +136,10 @@ By default, {product-name} runs with the UID 2000 and the GID 2000. On startup,
 $ docker run -it -e APP_UID=1234 -e APP_GID=4321 ghcr.io/inception-project/inception:{revnumber}
 ----
 
+NOTE: If the container is already started using a non-root UID, then `APP_UID` and `APP_GID` have no effect and also
+      no changes to the file ownerships in `/export` will be performed. This is e.g. the case when running a container using 
+      `-u` parameter or using the Kubernetes `runAsUser` setting. 
+
 == Docker Compose
 
 Using Docker Compose, you can manage multiple related containers. This section illustrates how to use
@@ -183,15 +214,5 @@ you mount the data to folders on your host.
 
 NOTE: Mind that you cannot arbitrarily switch between volume-managed and host-stored data. Choose wisely.
 
-=== Java options
-
-You can pass additional options to the Java runtime by extending the `JAVA_OPTS` variable in the
-Docker Compose script. To increase the available memory (RAM) to e.g. 4Gb, append `-Xmx4g`.
-
-[source,shell,subs="+attributes"]
-----
-- JAVA_OPTS=-Dspring.jpa.properties.hibernate.dialect.storage_engine=innodb -Xmx4g
-----
-
 There is a lot more that you can do using Docker and Docker Compose. Please see the link:https://docs.docker.com/compose/[docker-compose reference] for details.