From 409ca07fc0ac992a6fb454044ee628308e0771e0 Mon Sep 17 00:00:00 2001
From: Daniel Nephin <dnephin@docker.com>
Date: Fri, 12 May 2017 18:45:08 -0400
Subject: [PATCH] Document arg before from

Signed-off-by: Daniel Nephin <dnephin@docker.com>
Upstream-commit: 83a4afe2645d2e39cf6b10a86e9e681a7ff06eb2
Component: engine
---
 components/engine/docs/reference/builder.md | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/components/engine/docs/reference/builder.md b/components/engine/docs/reference/builder.md
index 9c28e8b47f..2571511b64 100644
--- a/components/engine/docs/reference/builder.md
+++ b/components/engine/docs/reference/builder.md
@@ -530,6 +530,17 @@ FROM extras:${CODE_VERSION}
 CMD  /code/run-extras
 ```
 
+To use the default value of an `ARG` declared before the first `FROM` use an
+`ARG` instruction without a value:
+
+```Dockerfile
+ARG  SETTINGS=default
+
+FROM busybox
+ARG  SETTINGS
+
+```
+
 ## RUN
 
 RUN has 2 forms: