Document command node

Author: willmostly

docs/installation.md

@@ -253,6 +253,15 @@ io/docs/concepts/configuration/secret/)
 is recommended to protect the  database credentials required for this 
 configuration.
 
+By default, the Trino Gateway process is started with the command 
+```shell
+java -XX:MinRAMPercentage=80.0 -XX:MaxRAMPercentage=80.0 -jar /usr/lib/trino/gateway-ha-jar-with-dependencies.jar /etc/gateway/config.yaml
+```
+This can be customized through the `command` node. This node accepts a list, which 
+should begin with an executable such as `java` or `bash`. The following list 
+elements are provided as arguments to the executable. It is not typically necessary
+to modify this node.
+
 #### Additional options
 
 To implement routing rules, create a ConfigMap from your routing rules yaml