Added documentation for gaia-pipeline/gaia#93" (#1)

content/getting-started/install-gaia.md

@@ -55,3 +55,37 @@ Other startup parameters are also available:
     	    If true, will print the version and immediately exit
         -worker string
     	    Number of worker gaia will use to execute pipelines in parallel (default "2")
+
+##### Run-time Arguments
+
+It is possible to define run-time arguments in three ways.
+
+###### As command-line arguments
+
+For example:
+
+    ./cmd/gaia/main -homepath=${PWD}/tmp -dev=true
+
+###### Environment Properties
+
+Environment variables can be used to overwrite any configuration settings / defaults that are already defined in Gaia.
+
+All Environment variables must be pre-fixed with `GAIA_` in order to avoid collision with other variables.
+
+For example:
+
+    export GAIA_PORT=9999
+    ./cmd/gaia/main -homepath=${PWD}/tmp -dev=true
+    # will start gaia with port 9999
+    ⇨ http server started on [::]:9999
+
+###### Configuration file
+
+Alternatively a configuration file can be used with all the properties that gaia defines, called .gaia_config.
+
+If this file is present it will be used to set things up. For example:
+
+    ❯ cat .gaia_config
+    port=9994
+    ./cmd/gaia/main -homepath=${PWD}/tmp -dev=true
+    ⇨ http server started on [::]:9994